CM From , joined Dec 1969, posts, RR: Posted (4 months 4 weeks 12 hours ago) and read 22112 times:
I'm starting a new conversation here.
In short:
>>The 787 uses Lithium-ion technology for its main and APU batteries. It is the first large commercial aircraft to use this battery technology in a large battery application.
>>Over a span of less than 2 weeks, 2 batteries in two separate 787s experienced thermal runaway events, causing a great deal of heat, smoke and, in the case of a JAL airplane on the ground in BOS, fire in the equipment bay.
>>After the first event, the NTSB opened an investigation and the FAA announced a full review of the 787 design and certification.
>>After the second event, ANA and JAL voluntarily grounded their 787 fleets, with the FAA issuing an AD to ground the US fleet the following day. All other regulators and airlines followed suit, with all 787s now grounded worldwide.
>>The FAA statement on the matter was, in part:
Quote: "As a result of an in-flight, Boeing 787 battery incident earlier today in Japan, the FAA will issue an emergency airworthiness directive (AD) to address a potential battery fire risk in the 787 and require operators to temporarily cease operations. Before further flight, operators of U.S.-registered, Boeing 787 aircraft must demonstrate to the Federal Aviation Administration (FAA) that the batteries are safe.
The FAA will work with the manufacturer and carriers to develop a corrective action plan to allow the U.S. 787 fleet to resume operations as quickly and safely as possible.
The in-flight Japanese battery incident followed an earlier 787 battery incident that occurred on the ground in Boston on January 7, 2013. The AD is prompted by this second incident involving a lithium ion battery. The battery failures resulted in release of flammable electrolytes, heat damage, and smoke on two Model 787 airplanes. The root cause of these failures is currently under investigation. These conditions, if not corrected, could result in damage to critical systems and structures, and the potential for fire in the electrical compartment.
Last Friday, the FAA announced a comprehensive review of the 787’s critical systems with the possibility of further action pending new data and information. In addition to the continuing review of the aircraft’s design, manufacture and assembly, the agency also will validate that 787 batteries and the battery system on the aircraft are in compliance with the special condition the agency issued as part of the aircraft’s certification."
>>There is a great deal of speculation about what the root cause of these events was and ways Boeing might address them in order to return the aircraft to service.
This thread is for the purpose of discussing the events, the FAA action, the technologies involved, and Boeing's effort to get the aircraft back into service. This thread is not for conspiracy theories, speculation about corruption in the certification process, or other issue not directly related to the events and the technologies involved. If you want to discuss those topics, please join the threads in Civ Av, where your comments will be quite welcomed.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 1, posted (4 months 4 weeks 11 hours ago) and read 22105 times:
Before those two incidents, the 787-8 had over 100,000 hours of in-service operation without either the Ship's or the APU battery suffering a fire or leaking electrolyte.
The NH airframe - JA804A - was delivered a year prior to the incident. It was the 9th 787 airframe to begin construction.
The JL airframe - JA829J - was delivered less than three weeks prior to the incident. It was the 84th 787 airframe to begin construction and the most recent 787 airframe delivered to a customer.
The Ship's Battery on JA804A (the NH airframe) had been replaced in October 2011. The stated reason for this was because the original battery could not start the engines. However, the Ship's Battery is not used to start the engines, so it may be a case of mistranslation (the original report was from Japanese media) or a miscommunication (the Ship's Battery can assist the APU battery in starting the APU).
There have been reports in the Japanese media that the two batteries may be from the same production batch.
The NTSB has been quoted as saying that the battery on JA829J was not subjected to charging voltages higher than it was designed to handle.
Japanese government officials have been quoted as saying that the battery on JA804A was subjected to charging voltages higher than it was designed to handle.
I have received an unconfirmed, third-hand report that a software update to the charging system was applied to a number of 787-8s recently, The details of this update are not known, though it has been said they changed the charging controls and algorithms. I also do not know which 787-8 airframes received this update (again, assuming such an update did occur).
kanban From United States of America, joined Jan 2008, 2500 posts, RR: 21 Reply 2, posted (4 months 4 weeks 10 hours ago) and read 22045 times:
CM, while I applaud the idea of a fact and data driven thread, the trollers and conspiracy theorists will find this sooner or later.
I'm afraid that it will still cause you, Tom, Stitch and others to be monitoring both forums and answering questions twice.
case inn point, I just finished a post in the other forum asking about the flammability or the electrolyte.. I could cut an paste it here however I'm leaving it as just one post.
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 3, posted (4 months 4 weeks 9 hours ago) and read 22020 times:
I hear a lot about excessive charging voltage (or lack of) but that's not really the factor in the failures I'm familiar with. You always have to use a high voltage for the final portion of the charge to get that last 10% or so. Cheap batteries might just have a thermistor to limit current when the battery get to a certain temperature, but there's no chance they used that on the 787. That algorithm has to be one that analyzes the voltage to current over time curve to sense end of charge and cut the voltage back down to maintenance, or whatever they call it. I'd hope that it also predicts battery problems by sensing abnormal charging curves.
This would be a lot more fun with some details of the charging/monitoring system. Damn their proprietary eyes anyhow.
I'm guessing a two part fix. Inspection, some replacement and quality control measures to get them airborne. Maybe a 90% charge limit or additional monitoring that wouldn't change anything to the extent of needing new, drawn out certification.
Long term, something that will take a while. A major change in the charging and monitoring in order to predict trouble and disconnect cells before grief ensues. Along with procedure to make sure sub par batteries don't find their way to a plane. Much depending on if the problem was design, production or something else.
I'm not sure if I'd put my money on Japanese government official comments. It's just too easy to prevent or detect higher than designed for voltage.
Cubsrule From United States of America, joined May 2004, 21294 posts, RR: 19 Reply 5, posted (4 months 4 weeks 9 hours ago) and read 22013 times:
One question I have is what assumptions Boeing and Airbus made when they incorporated lithium ion technology in to the 787 and 350. I understand the benefits, but what did Boeing and Airbus decide about thermal runaway and safety that is different today from when the 380 was developed with only minimal use of lithium ion batteries?
I can't decide whether I miss the tulip or the bowling shoe more
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 6, posted (4 months 4 weeks 9 hours ago) and read 21983 times:
I'm gonna repeat the post I just made in the civ/av thread after taking a look at the picture of the battery box after the flight (before it was cracked open):
On the surface, doesn't look too bad...I remember a battery box (containing a lead acid battery) looking like this after a coworker hooked up 28 volts DC to a poor Cessna 150 with a 12 volt electrical system and a dead battery... Fortunately, no one ever turned the master switch on in the 150 before the coworker realized the mistake. The mechanic was able to replace the fried battery and clean up the acid that boiled out of the battery box the same day. And yes, battery acid dripped down out the bottom of the cowling
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
CM From , joined Dec 1969, posts, RR: Reply 7, posted (4 months 4 weeks 9 hours ago) and read 21974 times:
Quoting Stitch (Reply 1): Before those two incidents, the 787-8 had over 100,000 hours of in-service operation without either the Ship's or the APU battery suffering a fire or leaking electrolyte.
Yes. Someone else suggested the total flying time between airline operations and flight test should be a bit over 100,000 hours. I could go verify that number as I have access to operational hours by tail number, but then I couldn't post on here about it - so let's call it 100,000 hours before the incidents. Sometimes it's better to not know things precisely!
Mike Sinnett (787 Chief Project Engineer) also stated the batteries have 1.3 million total operating hours, between labs, flight test airplanes and the in-service fleet.
Quoting kanban (Reply 2): CM, while I applaud the idea of a fact and data driven thread, the trollers and conspiracy theorists will find this sooner or later.
It is why I didn't post this link in the other thread. Perhaps this will give us a little time to discuss things intelligently.
Quoting nomadd22 (Reply 4): By the way. I probably missed it in the last 800 posts, but are we talking about cobalt oxide cathodes?
As far as I am aware, the batteries are Lithium Cobalt Oxide. At one point the batteries were Lithium Manganese, but my recollection is the chemistry was changed for some reason. It may have been to achieve longer on-wing life for the batteries, but I may not be remembering that exactly right.
Quoting kanban (Reply 109): we have discussed that the electrolyte is flammable.. but at what temperature? does the boiled extruded goo have the same or a significantly high ignition temperature? Does that "boiling" reduce the toxicity or encapsulate it so corrosion of surrounding metal is not at risk? My concern with building a double hull type containment is it would not allow the goo to cool which could exacerbate problems. If it runs out the port and hardens or vents from the a/c, it is less likely to ignite than if pooled around a thermal run away.
I don't know the answers to this, but I bet there is a battery expert or a fire chief out there who can help us with this. Let's hope one of those with these qualifications from the other thread drifts over.
Quoting rheinwaldner (Reply 117): The A350 needs equally good battery solutions as the 787 obvioulsly. Airbus even mentions an additional delay, if corrections are needed. The difference is, that the total installed battery capacity is much smaller, and yet the number of cells is higher. So a single cell is less vulnerable and has less capacity to do harm.
This comment caught my attention. I have a copy of an A350 systems description which includes this explanation of the A350 batteries:
Quote: Batteries DC generation:
Four identical Lithium-Ion batteries are connected to the 28 V DC network in order to:
- Ensure the No Break Power Transfer function
- Provide standby DC power
- Provide DC power on ground if AC power is not available .
Two out of the four batteries can provide temporary supply in an emergency configuration.
If only 2 of the 4 A350 batteries provide standby power, it is clear there was not an attempt by Airbus to reduce the size of the batteries by splitting them into 4 batteries instead of the traditional 2. Also, the standby power loads between the A350 and 787 will not be dramatically different. For example, the 787 and 777 have nearly identical standby power loads on the battery with the one difference being the need for additional capacity for electric braking on the 787 when the RAT drops below a certain speed. Because of this, I am of the opinion the A350 has 4 rather normal sized Lithium-ion batteries, not 4 half-sized batteries, as is being suggested. It adds relevance to this comment from the other thread:
Quoting Kaiarahi (Reply 111): The Airbus Director of Programs is on record as saying that an adverse outcome of the Boeing Li-Ion issue would have a significant impact on the A350.
817Dreamliiner From Montserrat, joined Jul 2008, 1490 posts, RR: 1 Reply 8, posted (4 months 4 weeks 8 hours ago) and read 21894 times:
Ive havent been following the previous threads on the topic due to the Boeing haters and trolls, but im glad you've started this thread here CM. I don't want to start speculating but here's my take on the battery accidents:
Quoting Stitch (Reply 1):
Before those two incidents, the 787-8 had over 100,000 hours of in-service operation without either the Ship's or the APU battery suffering a fire or leaking electrolyte.
And you can also include the many hours of flight testing that was done with the 6 test aircraft. The only exception would be the fire that occurred on ZA002, though im sure that is not related to the current battery issue.
Quoting Stitch (Reply 1): There have been reports in the Japanese media that the two batteries may be from the same production batch.
This is Exactly what I thought, when details of the second Incident were released. However, im sure this hasn't been fully proven as yet. As noted above the 787 has been in service for over a year, plus a year and a half of flight testing. If it really was a li-Ion battery design problem it should have came up in flight testing, which lead me to believe that the two batteries came from the same batch.
Quoting Stitch (Reply 1):
The Ship's Battery on JA804A (the NH airframe) had been replaced in October 2011. The stated reason for this was because the original battery could not start the engines. However, the Ship's Battery is not used to start the engines, so it may be a case of mistranslation (the original report was from Japanese media) or a miscommunication (the Ship's Battery can assist the APU battery in starting the APU).
Is that supposed to be October 2011 or 2012? Can you post the link to this?
Quoting Stitch (Reply 1): I have received an unconfirmed, third-hand report that a software update to the charging system was applied to a number of 787-8s recently, The details of this update are not known, though it has been said they changed the charging controls and algorithms. I also do not know which 787-8 airframes received this update (again, assuming such an update did occur).
While unconfirmed, it would be interesting if this did occur, again don't really want to speculate, but a software update causing the problem actually sounds plausible... What would be the process of testing a software update before its released to aircraft?
Also, I read a rumour on another site that the JL 787 might be written off, but as I said that's just a rumour. I don't think the damage was that bad to write it off...
Blast Reality, Burst it into shreds! Banishment, This World!
PITingres From United States of America, joined Dec 2007, 966 posts, RR: 12 Reply 10, posted (4 months 4 weeks 5 hours ago) and read 21679 times:
Curiosity question: How much room is there around the two battery enclosures? If part of the solution is to wrap the box in a sort of "drip tray", or rework the enclosure to give some level of individual cell containment, it's obviously going to make the total package larger. Is there any room to work with or is the battery going to have to maintain its current form factor?
Quoting kanban (Reply 2): ...the trollers and conspiracy theorists will find this sooner or later.
Well, I for one will have no compunction about using the delete post button. Let's hope the mods can keep this thread clean at least for a while.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 11, posted (4 months 4 weeks 5 hours ago) and read 21668 times:
There is a drawing of the forward and aft EE bays at the start of this PPrune thread, but I do not know how accurate they are. If the drawing is accurate to scale, then it looks like there may be room around it.
ADent in Reply 105 of the FAA Grounds 787 Part 4 (by iowaman Jan 21 2013 in Civil Aviation)#1 thread also showed a picture of the Ship's Battery on JA804A in-situ and it does look like there is a bit of extra room around it.
BEG2IAH From United States of America, joined Apr 2004, 840 posts, RR: 12 Reply 12, posted (4 months 4 weeks 4 hours ago) and read 21637 times:
Quoting kanban (Reply 2): I just finished a post in the other forum asking about the flammability or the electrolyte..
I've been searching for the answer and what I found so far says the electrolyte is flammable. Actually, when you read more it says the vapors are flammable and they would need a source of ignition to burn. It does not self ignite! There is a lot of research into new electrolytes that add flame retardants, such as this one: http://www.targray.com/li-ion-battery/electrolyte.php
Here are the sources and excerpts:
1) http://www.sbir.gov/sbirsearch/detail/15939
Commercially available lithium-ion cells use an electrolyte containing a mixture of organic carbonate solvents combined with lithium hexafluorophosphate (LiPF6). These electrolytes have significant disadvantages limiting the performance and safety of lithium-ion batteries. First, the solvents are volatile and flammable, leading to safety issues during production, storage and use of batteries and their behavior under abuse conditions. Second, LiPF6 is not hydrolytically or thermally stable in organic carbonates, leading to degradation of electrolyte, rise in electrode/electrolyte interface impedance, dissolution of active cathode materials and limited battery life. Thirdly, present electrolyte solutions appear to be reactive towards cathode materials at high voltages, which contribute to battery performance deterioration. It also prevents further development of future higher energy cells with 5V cathode materials. Finally, present electrolyte formulations are always a compromise; no one mixture of the solvents has been shown to work well at both low and high temperatures.
2) http://prod.sandia.gov/techlib/access-control.cgi/2012/129186.pdf
For lithium ion rechargeable batteries, these electrolytes are almost universally based on lithium hexafluorophosphate (LiPF6) salts with combinations of linear and cyclic alkyl carbonates. These electrolytes enable the use of lithium as the negative electrode active component and results in the high power and energy densities characteristic of the Li-ion chemistries. However, these organic electrolyte solvents have high volatility and flammability that pose a serious safety issue for their use in the consumer and transportation markets. For example, gas generation in Li-ion cells under abuse conditions has an effect on safety because gas production, if generated at sufficient pressure will vent flammable solvent vapor into the surrounding environment. The resulting fuel-air mixture can be quite explosive and only requires an ignition source to ignite the vapors. LiPF6 is known to react with carbonate solvents at elevated temperature and in the presence of moisture to generate large gas volumes of decomposition products [2-4].
4) http://144.206.159.178/ft/641/92454/1607448.pdf
The electrolyte for these batteries typically consists of ethylene carbonate with a high dielectric constant and an alkyl carbonate as a low viscosity solvent containing the LiPF6 salt. These solvents are flammable. When the internal pressure of the battery increases and the battery is mechanically destroyed, the electrolyte could be led to the dangerous situations such as fire and explosion. These accidents were thought to be related to the flammability of common carbonate-based electrolytes. Therefore, it has been becoming important to find effective method to suppress the flammability of lithium-ion batteries.
5) Wikipedia (this talks about the properties of LiPF6 salt, which by itself is not flammable) http://en.wikipedia.org/wiki/Lithium_hexafluorophosphate
The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a flash point requires an ignition source. At the flash point, the vapor may cease to burn when the source of ignition is removed. The flash point is not to be confused with the autoignition temperature, which does not require an ignition source, or the fire point, the temperature at which the vapor continues to burn after being ignited. Neither the flash point nor the fire point is dependent on the temperature of the ignition source, which is much higher.
I'm fundamentally challenged when it comes to chemistry (just a dumb economist here) so I hope this helps a bit. Please don't ask me for any follow ups.
[Edited 2013-01-22 17:50:20]
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kanban From United States of America, joined Jan 2008, 2500 posts, RR: 21 Reply 13, posted (4 months 4 weeks 1 hour ago) and read 21520 times:
Quoting BEG2IAH (Reply 17): I'm fundamentally challenged when it comes to chemistry
I am also.. failed chemistry so bad had to switch to an art major..
Thanks , some of it made sense.. hopefully tdscanuck or CM will translate to layman's terms.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 14, posted (4 months 4 weeks 1 hour ago) and read 21517 times:
Quoting kanban (Reply 20): I am also.. failed chemistry so bad had to switch to an art major..
Thanks , some of it made sense.. hopefully tdscanuck or CM will translate to layman's terms.
Hated chemistry so much I took Chemistry AP in high school just so I could avoid taking it as an undergraduate. Never took a chemistry course again, although it kept popping up annoyingly in other contexts.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 15, posted (4 months 4 weeks ago) and read 21493 times:
Quoting BEG2IAH (Reply 17): I've been searching for the answer and what I found so far says the electrolyte is flammable. Actually, when you read more it says the vapors are flammable and they would need a source of ignition to burn. It does not self ignite!
So it is possible that with the outflow valve actively clearing the air in the EE bay, then even an electrolyte stream might not ignite due to the flammable vapors being expelled from the bay?
CALTECH From Poland, joined May 2007, 1603 posts, RR: 22 Reply 16, posted (4 months 4 weeks ago) and read 21486 times:
Quoting CM (Reply 7): As far as I am aware, the batteries are Lithium Cobalt Oxide. At one point the batteries were Lithium Manganese, but my recollection is the chemistry was changed for some reason. It may have been to achieve longer on-wing life for the batteries, but I may not be remembering that exactly right.
As relayed to us, the composition of the electrolyte was changed as the batteries were only lasting 6 months. With the new composition, battery service life has gone up to approx 4 years. Oxides had been added to the composition is what has been said.
These 787 batteries, they are high energy and high heat. There were concerns about the temperature generated during periodic main/APU battery capacity checks to be performed on the aircraft, as proposed. Believe our airline is so concerned with the heat generated and relying on a test box to prevent a thermal runaway durng the capacity check, that the batteries will be removed from the aircraft for these capacity checks.
Also, unlike the Ni-Cad batteries, if a bad cell is encountered on these 787 batteries, it supposedly needs all the cells replaced for cell voltage balancing.
787 has a voltage below which it cannot be recharged.The battery has an auto-shutdown program to prevents cell damage from further voltage loss.
In tests, the 787 batteries have been dropped from aircraft E&E hatch height, and then steel rods were driven through the battery, all with no explosive effect. It hasbeen said that the new Li-ion chemistry in this battery – the electrolyte is a paste composed mainly of Li ion solution, cobalt, and a proprietary powder – is a much more stable chemistry than earlier and other Li-ion chemistries.
It has been said that there is no going back to Ni-Cad. This is a interesting aircraft. The leap in new technologies will take some getting used to. Can not wait to fly on one .
BEG2IAH From United States of America, joined Apr 2004, 840 posts, RR: 12 Reply 17, posted (4 months 4 weeks ago) and read 21463 times:
Quoting CALTECH (Reply 23): In tests, the 787 batteries have been dropped from aircraft E&E hatch height, and then steel rods were driven through the battery, all with no explosive effect. It hasbeen said that the new Li-ion chemistry in this battery – the electrolyte is a paste composed mainly of Li ion solution, cobalt, and a proprietary powder – is a much more stable chemistry than earlier and other Li-ion chemistries.
CALTECH, would that mean "flame retardant" might be part of that new proprietary chemistry?
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CM From , joined Dec 1969, posts, RR: Reply 18, posted (4 months 3 weeks 6 days 23 hours ago) and read 21570 times:
Quoting 817Dreamliiner (Reply 8): Also, I read a rumour on another site that the JL 787 might be written off, but as I said that's just a rumour. I don't think the damage was that bad to write it off...
I don't have any direct knowledge of either battery incident, but the photos I've seen of the JL airplane sure wouldn't point in this direction. Let's imagine an extreme scenario: if the entire rack which housed the battery needed to be replaced (P150 panel, WIPS controller, APU battery charger, etc), plus the airplane required a major structural repair in the bilge area below the battery, I am still confident the cost of this repair would fall far short of what would make the insurer consider writing the frame off as a hull loss. I would guess the airplane to be valued by an appraiser at between $125 and $150 million. The cost of the repair would need to approach 50% of this before it would be written off.
Quoting kanban (Reply 20): hopefully tdscanuck or CM will translate to layman's terms.
Not to create a theme, but Would you believe you can get both mechanical and aero degrees with nothing more than grade 10 chemistry? I hated it, did poorly in it, and retained none of it. I will truly be of no use to you on topics of chemistry.
Quoting Stitch (Reply 22): So it is possible that with the outflow valve actively clearing the air in the EE bay, then even an electrolyte stream might not ignite due to the flammable vapors being expelled from the bay?
I doubt this very much. The normal ventilation of the equipment bays is designed with just enough pressure differential to keep steady airflow through the bay for cooling reasons. There are fans in the system, but the negative pressure at the outflow valve will keep things moving even without them. If smoke is detected, there is a second "outflow valve" (called the override valve) which automatically opens and increases the venting of the bay. Even with this second valve open, the intent is to have just enough negative pressure relative to the rest of the airplane that it would not be possible for smoke to migrate from the equipment bay into the main deck. It is by no means a massive vacuum evacuating the bay. A man wearing a toupee would certainly be safe in there, even with the override valve open
Quoting CALTECH (Reply 23): It has been said that there is no going back to Ni-Cad.
I know many in the other threads were asking why Boeing is not just making a Ni-Cd battery for the 787 and being done with this issue altogether. There are distinct differences in the power provided by each battery, which is why I believe your statement is mostly correct; a swap of battery technologies might be possible, but it would not be straightforward. A Ni-Cd cell has a marked voltage decay from peak charge to its depleted state. A Li-ion cell holds a much more constant voltage as it discharges. Among the many desirable aspects of Li-ion batteries, I believe the power quality they produce (and systems which were designed to take advantage of it) may make it very hard for Boeing to change battery types at this point.
CALTECH From Poland, joined May 2007, 1603 posts, RR: 22 Reply 19, posted (4 months 3 weeks 6 days 22 hours ago) and read 21501 times:
Quoting BEG2IAH (Reply 24): CALTECH, would that mean "flame retardant" might be part of that new proprietary chemistry?
As in adding 'flame retardant' ? No. It is just a more stable chemistry. And the new composition of the electrolyte was done quite some time ago, they may play with it some more.
Quoting CM (Reply 25): I know many in the other threads were asking why Boeing is not just making a Ni-Cd battery for the 787 and being done with this issue altogether. There are distinct differences in the power provided by each battery, which is why I believe your statement is mostly correct; a swap of battery technologies might be possible, but it would not be straightforward. A Ni-Cd cell has a marked voltage decay from peak charge to its depleted state. A Li-ion cell holds a much more constant voltage as it discharges. Among the many desirable aspects of Li-ion batteries, I believe the power quality they produce (and systems which were designed to take advantage of it) may make it very hard for Boeing to change battery types at this point.
Spot on. It is and could be possible to go to a Ni-Cad battery, but very unlikely for all those reasons you posted, at least up to this pont in time.
kanban From United States of America, joined Jan 2008, 2500 posts, RR: 21 Reply 20, posted (4 months 3 weeks 6 days 22 hours ago) and read 21533 times:
KC135Hydraulics From United States of America, joined Nov 2012, 165 posts, RR: 0 Reply 21, posted (4 months 3 weeks 6 days 20 hours ago) and read 21498 times:
Hey guys,
Much prefer the discussion on this forum than on civil aviation! I also posted this picture there, but I thought it'd be interesting for conversation here. These are the batteries on the KC-135. They are lead-acid, 28v. These are kept in the latrine... as you can see, the toilet on the left and the urinal can to the right.
Battery charger controller is mounted just above the circuit breaker panel.
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 22, posted (4 months 3 weeks 6 days 18 hours ago) and read 21402 times:
Quoting CALTECH (Reply 23): Also, unlike the Ni-Cad batteries, if a bad cell is encountered on these 787 batteries, it supposedly needs all the cells replaced for cell voltage balancing.
It's more important for the cells to be perfectly matched in a series to prevent overcharging one of them with Lithium.
Quoting CALTECH (Reply 23): It hasbeen said that the new Li-ion chemistry in this battery – the electrolyte is a paste composed mainly of Li ion solution, cobalt, and a proprietary powder – is a much more stable chemistry than earlier and other Li-ion chemistries.
I don't have anything to back it up, but we'd always gathered that the cobalt chemistry was one of the less safe ones and was used for greater capacity and voltage. An iron oxide setup would have needed one more cell to get the same voltage. I gather you're referring to the proprietary solution, and not being cobalt based.
Quote:
Japan Transport Safety Board chairman Norihiro Goto told reporters the jet's data recorder showed the main battery, used to power many electrical systems on the jet, did not exceed its maximum voltage. That contradicts an earlier assertion by the agency as it investigates with the U.S. Federal Aviation Administration.
All 50 of the 787 Dreamliners that Boeing has delivered to airlines were grounded after the emergency landing by the ANA flight in western Japan on Jan. 16. Boeing has halted deliveries of new planes until it can address the electrical problems.
Goto said the maximum voltage recorded for the battery was 31 volts, which was below its 32 volt limit. But the data also showed a sudden, unexplained drop in the battery's voltage, he said.
Aircraft do not usually use the kind of lithium ion battery chosen for the 787, and investigators are still struggling to figure out what may have gone wrong.
"It's not that it is difficult, but that we are not so familiar with it," Goto said.
The Transport Safety Board said it also will study the aircraft's auxiliary battery and compare data from each.
So no overcharging at the battery level for the 2 failures..
and Japanese backpedalling by the way
rcair1 From United States of America, joined Oct 2009, 950 posts, RR: 25 Reply 24, posted (4 months 3 weeks 6 days 15 hours ago) and read 21303 times:
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I, too, have tried to escape the other thread here. Thanks to CM for starting it.
I posted the following in the other thread last night after spending a lot of time doing research into new areas.
To my chagrin - I found that some of the information I had posted on Li-Ion batteries applies only to Li primary (non-rechargeable) batteries.
My apologies to all for being incorrect!
------
So - I got really tired of reading patents today and so I started looking for concrete new data on Li-Ion battery fire danger and suppression techniques. I even spent a fair amount of time reading about "bricking" your Telsa.
I've discovered some errors in what has been posted here, including errors that I made.
To be clear - the information I provided was based on training I received in an alternative fuels class I took about 4 years ago - and it seems like the understanding is evolving.
First - the biggest source of misunderstanding is confusing Lithium and Li-Ion battery chemistry and the approaches to fighting a fire in both cases.
In Lithium battery fires - these are non-rechargable Li Batteries - known as primary batteries - there is significant metallic Lithium. This is a true metal class fire and requires class D extinguishing agents. Conventional extinguishers - ABC as well as Halon, and most especially water - do not work.
-> My training was focused on this - and either I missed the following, or it was not covered.
In Lithium-Ion rechargeable batteries - secondary batteries - there is little metallic Lithium. You can use water or class ABC extinguishing agents - though the efficacy of them is unproven. The primary fire hazard for a Li-Ion battery is 2 fold - heat due to thermal runaway and flammable electrolyte/vent gas. The big difference - which I have just learned - is that the electrolyte in a Li-Ion battery is more flammable that the electrolyte in other batteries (like NiCad or NiMH) because it is not water base. Those other electrolytes pose much higher corrosion and toxicity concerns, but lower fire concerns.
Tests seem to indicate that conventional techniques, if they could be applied, would be effective in extinguishing the flame - however, the danger posed by re-kindle is major.
For instance, Halon 1301 is shown to be effective extinguishing the flame (electrolyte/gas), but not cooling the battery. If you use Halon, you will likely face re-kindle. An effective suppression would need to persist - to remain on the fire long enough to extinguish re-kindles long enough for thermal runaway to terminate. Water is effective in cooling, except that the design of the battery makes it difficult/impossible to apply well enough to overcome the heating of a thermal runaway.
It is interesting to note the 2 methods discussed for aircrews to deal with runaway fires in consumer batteries (laptops) are to 1) douse them repeatedly with water or 2) put them in a containment bag. The containment bag is designed to contain the heat long enough for runaway to terminate and the fire to go out. No effort is made to contain vent gasses in these containment bags. The reports I read seemed to indicate the containment bag was a better approach - it was surer.
It is also unclear if "spreading" the electrolyte by washing it around with water is a concern.
So - the primary issue extinguishing a Li-Ion battery fire is that, while you can potentially extinguish the 'flame' you cannot effectively cool a battery in thermal runaway well enough to prevent re-kindle of either the electrolyte or gasses being expelled. A Halon extinguishing system in the EE bay would be ineffective - it may put out flames (if they are outside the containment), but would not cool the battery. Thermal runaway would continue and re-kindle would be likely.
BTW - the data I could find so far indicates that the flammability limit LFL to UFL for vented gasses is small. LFL is the concentration in air below which the gas is non-flammable (too lean) and UFL is the concentration above which it is not flammable (too rich). A narrow flammability range means that an effective control method is to either concentrate or disperse the gas. The latter is obviously the better choice. Therefore - effective and positive ventilation is important.
One of the better references I've been studying is research performed by the Fire Protection Research Foundation - funded by the NFPA (National Fire Protection Association) - an organization I work with a lot.
The report I reference is located at the link below and was dated July 2011. I might refer you to Chapter 6 (page 84) and beyond.
The obvious question one may ask is does this change my opinion on the situation the 787 and Boeing face. The answer I have is - I'm sure - not going to satisfy some. Simply stated - I don't know yet - I need more data.
It seems that containment and venting (if those are not contradictory terms) are still the best approach based on the data I have seen. Vent the gas to keep it below LFL. Contain the fire so it says in the 'box'.
I do have a concern about the leaked electrolyte. Based on the new knowledge I spent the afternoon gaining (not from a.net by the way), my level of concern is increased. If it is flammable - and it appears it may be (since we do not know the exact composition of the Yuasa batteries, I can't say for sure) it represents a hazard. Is it a hazard that can be managed by placing it in a location where, if ignited, it will consume itself and burn out without the fire extending - then - no. If it the fire could extend - then yes. I would caution you that even the NFPA report I'm citing states that Li and Li-Ion battery chemistry varies dramatically and they are careful not to point out that testing all the types of chemistry is beyond the scope of their research.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 25, posted (4 months 3 weeks 6 days 15 hours ago) and read 21518 times:
Quoting nomadd22 (Reply 30): I don't have anything to back it up, but we'd always gathered that the cobalt chemistry was one of the less safe ones and was used for greater capacity and voltage.
That does appear to be the case with Lithium cobalt oxide (which is what the 787's batteries use). They are more susceptible to thermal runaway in cases of abuse such as high temperature operation (>130ºC) or overcharging.
Lithium nickel manganese cobalt appear to provide most of the benefits of lithium cobalt oxide, but is safer. This formulation was created in 2008, so it was not available at the time of the 787's development, but if it could be retrofitted into the Yuasa cels, it might provide the necessary additional level of safety.
Quoting nomadd22 (Reply 30): An iron oxide setup would have needed one more cell to get the same voltage.
In that case, I wonder if there is enough space in the current bay location to allow a slightly larger battery using this cathode chemical.
rcair1 From United States of America, joined Oct 2009, 950 posts, RR: 25 Reply 26, posted (4 months 3 weeks 6 days 15 hours ago) and read 21451 times:
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Quoting CM (Reply 7): I don't know the answers to this, but I bet there is a battery expert or a fire chief out there who can help us with this. Let's hope one of those with these qualifications from the other thread drifts over
The NFPA report I mentioned (re-linked here) discusses the energy content and flammability of a 16850 cell- this a typical cell used in consumer batteries. Clearly - this battery is different in the one in the 787 which is a prismatic design - but it can give us some idea of the energy content of an example battery of this type.
They do note that calculating the energy content here is difficult - this is based on a model used for fire suppression estimation. (pp88)
In the 16850 cell - they estimated the cell contain 3-6 g of electrolyte (pp 89) but to be conservative, they base the calculations on 10g of electrolyte and 1.6g of poly based separator. Based on the heat of combustion for typical materials, they estimate that battery has ~280kJ in the material. The battery itself can contain between 25 and 40 kJ of energy - so the total energy content of the battery is on the order of 300-320 kJ.
Now - this is for a n 16850 cell - this is the little cylindrical battery - kind of like a AA sized battery - used in consumer packs and they note that this estimate is not good for larger batteries because the size and composition is much different.
Suffice it to say - there is a significant amount of energy in the electrolyte - more than the stored energy.
Regarding flammability - not energy content - the report is less revealing. This is because the chemistry is so variable. What they do discuss is the flammability of vent gasses in terms of UFL and LFL - the range of concentrations where the vent gas is flammable. I refer you to the beginning of chapter 6 - PP 86.
According to tests at Sandia - the vent gases include H2, CO, CO2, CH4, C2H4, C2H6 and some others in vary small quantities. Of those gases - CO2 is the most prevalent - in the 65% range. C2H4 is next (15%ish) followed by CO and H2. CO2, of course, is not combustible - so the most prevalent gas in these test will act more like an extinguishing agent - by displacing O2 and dispersing the other vent gases.
H and CO have large flammability ranges (4-75% and 12.5 to 74%), CH4's pretty narrow (say 1.8 to 9% +/-1) (pp87)
To determine the flammability of this gas - you must vent it into your test atmosphere with designated air flow rates and calculate the mixture present. If the mixture - for a particular gas - is within the flammability limit - and there is appropriate oxygen - and there is an ignition source - you can get a fire. There are way too many variables here that I don't know to be able to even approach the question of flammability of vent gasses in the 787 battery in a battery fire/vent.
You would have to know:
- The actual vent gasses for THIS battery
- The rate of venting
- The rate of airflow around the venting
- The concentration of oxygen and other gasses
I suspect that inside the containment - no way - it is too rich. Outside - if there is good airflow - to low. There may be an issue right at the vent location - where the gasses are vented to the atmosphere. There may be a location where the mixture is such that fire could occur. We talk about that when entering propane leak areas. Far enough away - not enough propane. Up close - too much. But somewhere in the middle, you will walk through a combustible mixture.
-- Regarding suppression mechanisms.
Halon - in particular in treating the vent gases is effective - it narrows the flammability range.
From pp 99
"When small quantities of Halon are added to a fuel/air mixture, they narrow the range
in which that mixture is flammable.176 Halon is far more effective at narrowing the flammable
range than an inert diluent. If sufficient Halon is added, the flammable range of a mixture, even
at an elevated temperature, is eliminated and the mixture cannot be ignited."
Unfortunately - Halon is a problem.
"Note that production of Halon was banned by the Montreal Protocols, as this material contributes to the destruction of
the ozone layer. Halon in use today is from recycled sources only, primarily for protection of aircraft."
moose135 From United States of America, joined Oct 2004, 2020 posts, RR: 12 Reply 27, posted (4 months 3 weeks 6 days 14 hours ago) and read 21549 times:
Quoting CM (Reply 25): I am still confident the cost of this repair would fall far short of what would make the insurer consider writing the frame off as a hull loss. I would guess the airplane to be valued by an appraiser at between $125 and $150 million. The cost of the repair would need to approach 50% of this before it would be written off.
If it even got to that point, I suspect Boeing might eat some (or most) of the cost of repairs simply to avoid the PR issue of having a 787 written off at this stage of the game.
Quoting KC135Hydraulics (Reply 29): These are the batteries on the KC-135. They are lead-acid, 28v. These are kept in the latrine... as you can see, the toilet on the left and the urinal can to the right.
And it was never that bright in there. Aim carefully!
Let me add my thanks to CM for starting this thread - it was difficult to find the useful information hiding amongst the dreck in those CivAv threads.
Kaiarahi From Canada, joined Jul 2009, 2587 posts, RR: 24 Reply 28, posted (4 months 3 weeks 6 days 12 hours ago) and read 21398 times:
NTSB update from Jan 20 that I haven't seen referenced (although I could have missed it on the CivAv compost heap). Major points:
JL battery being disassembled for examination of cell internal components.
Test plans developed for various components:
The team has developed test plans for the various components removed from the aircraft, including the battery management unit (for the APU battery), the APU controller, the battery charger and the start power unit. On Tuesday, the group will convene in Arizona to test and examine the battery charger and download nonvolatile memory from the APU controller. Several other components have been sent for download or examination to Boeing's facility in Seattle and manufacturer's facilities in Japan.
Does any of this (e.g. testing the APU controller / start power unit) suggest an investigative direction?
JTSB and BEA have accredited representatives to the NTSB investigation (there's no indication on the BEA site that they've started their own, contrary to "info" on the other thread).
"Attending emergency services found no trace of fire, however traces of smoke released from the electric compartment were found on the outside of the fuselage. Investigators found the main battery, a lithium ion battery same type as the APU battery, had buckled at the upper cover and was leaking, the inside showed hydrocarbons. The main battery was removed from the aircraft on Jan 17th, the undamaged APU battery was removed from the aircraft on Jan 18th, following a first examination of the main battery on Jan 20th the battery has been dispatched for detailed examination on Jan 22nd."
the posting goes on to show pictures of both the a/c's batteries side by side.
The only thing puzzling is the insistence that the residue under the fuselage is 'smoke' residue rather than liquified electrolyte residue.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 30, posted (4 months 3 weeks 6 days 8 hours ago) and read 21212 times:
Quoting Kaiarahi (Reply 42): Does any of this (e.g. testing the APU controller / start power unit) suggest an investigative direction?
I'm not sure...it looks like they took the battery and everything the battery interfaces with. That seems more like the shotgun approach (investigate everything in the hope that we find the culprit).
If I remember (not sure of the source of the info, though), the APU was running in BOS. Which means it was started relatively recently before the fire was discovered - although we don't know if it was started before powering off the engines.
TheSultanOfWing From El Salvador, joined Dec 2012, 97 posts, RR: 0 Reply 32, posted (4 months 3 weeks 6 days 7 hours ago) and read 21079 times:
Folks,
I tried to have this question answered in the "other" dreaded thread as well, so here goes:
Is Boeing physically checking each airframe delivered, in other words: are they dispatching personnel to NRT, SCL, DOH etc? Or is it just a check in general, concentrating on the batteries?
Same question for the NTSB, or do they leave that the local authorities in each country?
Has the B787 in question left Takamatsu yet?
Thanks,
FH
I feel like the A318 at times: I am probably worth more parted out than as a whole.
airmagnac From Germany, joined Apr 2012, 161 posts, RR: 40 Reply 33, posted (4 months 3 weeks 6 days 7 hours ago) and read 21080 times:
Quoting CM:
here are some personal thoughts on the FAA statement:
[...]
The statement talks about the failure mode, the conditions it may create, and the potential consequences:
Failure Mode:
>> Battery failure by thermal runaway
Conditions it may Create:
>> Heat
>> Release of flammable electrolytes
>> Smoke
>> Fire
Potential Consequences:
>>Damage to critical systems and structure
Hi CM (and everyone)
I've been meaning to build on your thoughts in reply 38 from FAA Grounds 787 Part 4 (by iowaman Jan 21 2013 in Civil Aviation) for a couple of days, but I don't have much free time.
Anyway, I used your ideas to propose this somewhat crude (!!) fault tree representation :
It starts with the root causes, which remain unknown, and could be a problem from any one among design, manufacture, assembly, in flight ops, ground ops, maintenance ops..., and probably a combination of the above.
I represented these root causes at a same level '-x' (-xvious event happened (everything is represented as independant - big approximation...)
Again this is very simplified, and is meant for illustration purposes only.
I did modify a little your interpretation of the "fire" part ; I kept the "EE bay fire" stated by the FAA, but put it as a terminal consequence. But I added a "battery fire" as immediate consequence, which could itself lead to both "bay fire" and "system damage".
Assuming the Boeing design and failure analysis people are competent - which I will - the battery thermal runaway and its consequences (= the lower part of the tree, levels >= 0) are not a surprise, and should have been considered and the relevant occurance probabilities would have been analyzed and calculated. This would be based on a model of the fire/smoke/electrolyte propagation, itself based on some hypotheses.
As I see it, the problem is :
......1) the fact that 2 events happened in rapid succession could indicate that the calculated probability of the main failure is lower than it should be, if this is a systemic failure. The probabilities of all the subsequent events would be automatically increased, resulting in the terminal consequences having too high a probability (>1e-9) and/or
......2) the observations made after the two incidents could invalidate the hypotheses used to calculate the conditional probabilities of the consequences (arrows leading to events at levels >= 1). The resulting calculated probabilities for the terminal consequences would then be invalidated also. If the model seems to be very wrong, the probabilities could be sufficiently off to climb above the 1e-9 threshold.
Alternative 2) seems to unlikely to me (or at least, unlikely that the hypotheses would be so wrong as to invalidate all calculations). And if this is a defect of a limited batch of equipment, then alternative 1) should be cleared also.
At least that is what I see so far, with the little data publicly available
CM From , joined Dec 1969, posts, RR: Reply 34, posted (4 months 3 weeks 6 days 5 hours ago) and read 20963 times:
Quoting airmagnac (Reply 50): I used your ideas to propose this somewhat crude (!!) fault tree representation :
Thanks for this. I always do better when I can visualize things! Just a couple quick comments:
First, I agree with your modification and distinguishing between a fire inside the containment and a fire in the equipment bay. That's a good modification/improvement to how I had worded things before.
Regarding #1. I agree. It seems most likely that the original fault tree had a probability error in Level X or Level -1 than the alternative - that we just witnessed two remote or perhaps even extremely remote events within a relatively small number of operational hours. Lightning doesn't strike twice...
One of the possible precursors to a runaway event is a manufacturing defect inside the battery cell. The manufacturing process will have been studied and approved to validate that the likelihood of this defect occurring during manufacturing, so that some quantifiable probability can be inserted into the fault tree. Not personally knowing any details of the 787 battery fault tree, this probability could range anywhere from 1 to 1e-9, although I would be shocked if the probability wasn't quite remote. If the failure is at this level and if 1e-9 is in reality 2 in 200, you are absolutely correct that everything downstream needs to be revisited.
The absolutists in the other thread are quite hung up on the thermal runaway of the battery - that it must not happen under any circumstance, no exceptions. I think we both know this is not true for any battery on any airplane, and this is not how the 787's problem will be solved. From a "Failure Modes & Effects" standpoint, they are only thinking about the FM, they just assume the "E in FME is catastrophic or otherwise unacceptable. That sentiment in Civ Av (probably because they don't understand how AC 25.1309 or the EASA equivalent works) has them looking for solutions which will likely never even be considered by Boeing and the FAA.
Instead, I say let the fault tree take us to the Level 0 event with an assumed probability of 1. If I was involved with trying to solve this, I would certainly assign a team to go see how they would solve the problem under that assumption - that every battery will go into thermal runaway at some point in its life. This would get the team focused on mitigating the effects of the event and may result in an acceptable fault tree, even with a battery that occasionally misbehaves. (Please note, I'm not saying I would accept the demonstrated failure rate of the batteries, but you get my point)
Lastly, I probably should re-state the fact I was not involved at all in the 787 battery design. With that disclosure, you can take my comments as from someone who is well informed about Boeing design practices and FAA certification, but not from an expert on the failure modes within this particular system.
PITingres From United States of America, joined Dec 2007, 966 posts, RR: 12 Reply 35, posted (4 months 3 weeks 6 days 5 hours ago) and read 20937 times:
I might be one of the (few?) non-chemistry-haters here, although I never studied it at an advanced level. (Did plenty of messing around in the basement as a teen, though.) I happened to run across this haiku in the "Lamentations on Chemistry" blog and thought it might amuse the folks here:
Mighty exotherm
Sleeping in reaction mass
Please stay home today
rcair1 From United States of America, joined Oct 2009, 950 posts, RR: 25 Reply 36, posted (4 months 3 weeks 6 days 5 hours ago) and read 20882 times:
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Quoting airmagnac (Reply 50): Anyway, I used your ideas to propose this somewhat crude (!!) fault tree representation :
I like your representation. I do have some comments.
For instance, you show the "release of flammable electrolyte" and "battery fire inside container" pointing at "EE bay fire.
I don't think that a fire inside the container would combine with electrolyte outside in that way. I think is is more likely that "heat" would combine with 'release" and lead to EE bay fire (not that I think it is likely).
You need to add 'venting gases' too. It may be they are more likely to ignite than the electrolyte - I don't know.
Also - the presence of heat and electrolyte would not, in all cases, lead to fire. Instead - there would be a probability factor (sent that become involved (extension), then it could damage critical components.
If we assume the underlying failure rate is constant, i.e. we are not dealing with an infant mortality issue
If we assume the battery system has accumulated 1.3 million hours of operation (as stated by Boeing exec)
Do you think Poisson is the right distribution model to apply here? I know we don't know the underlying failure mechanism but I have a tough time thinking of any mechanism that would have a constant rate with time.
Quoting TheSultanOfWing (Reply 49): Is Boeing physically checking each airframe delivered, in other words: are they dispatching personnel to NRT, SCL, DOH etc? Or is it just a check in general, concentrating on the batteries?
I doubt they're doing that yet...unless they already know what they're looking for and that just hasn't been made public yet. As soon as they do know what to look for, I'd expect a joint NTSB/FAA/JCAB/Boeing/Yuasa team to visit all 50 airplanes.
Quoting TheSultanOfWing (Reply 49): Same question for the NTSB, or do they leave that the local authorities in each country?
By treaty, the local authorities own the investigation. So NTSB has the Boston event and JCAB (or whoever their investigative branch is) has the Japan event. In many countries the local authorities have very limited resources and request help from a bigger outside agency (BEA, NTSB, etc.). Japan, however, has a very good investigation board so they wouldn't drag NTSB in on that basis. However, it's normal courtesy to bring the investigating body from the country of certification in. And, when two events might be coupled, they cooperate.
Quoting PITingres (Reply 52): I happened to run across this haiku in the "Lamentations on Chemistry" blog and thought it might amuse the folks here:
Mighty exotherm
Sleeping in reaction mass
Please stay home today
The very sardonic part of me wants to see this written in as a footnote to a battery spec somewhere.
Quoting rcair1 (Reply 53): You need to add 'venting gases' too. It may be they are more likely to ignite than the electrolyte - I don't know.
In one of the bazillion posts buried in the CivAv theads, somebody stated that it was only the gases that were flammable (or electrolyte vapour, also a gas). However, I have no idea if that was accurate.
I thought a couple of questions may perhaps be better nested here:
Quote: I wonder whether the container which serves as fire/leak shield for Li-ion batteries may be reflecting back into the battery the (strong) electromagnetic fields which are produced by the movement of lithium ions within it. Depending on the 3D geometry of the container, such retro-reflection may become amplified and focused on a local point within the battery. If such is the case, this point may become susceptible to heat damage and maybe ultimately lead to thermal runaway.
Is this shielding container metallic in the first place? If yes, it is designed to preclude retro-reflection of electromagnetic radiation produced internally by the battery?
Quote:
DC current through a relatively straight path isn't going to produce that much of a field. I don't know if they have something as simple as a large filter cap to keep high speed current pulses out of the battery.
But, it must be either something like that, where field conditions don't match lab conditions or the batteries being used are different than the ones that were tested. I'd think they would have had a full size pack in the the same boxes they'd be using in the plane being tortured under all possible environments for certification.
Quote: The EM field will however peak as the current goes from nil to full discharge current. Given the power of the APU batteries, I dare say that the peak EM field on initial discharge could be quite significant.
Quote: That's what I meant regarding the filter cap. It slows down the rise and fall time of the current changes and reduces the fields caused by such quite a bit.
I trust there is a filter cap in place on these powerful batteries. Can it be ruled out as a causal factor in the thermal runaway with any degree of confidence?
Tristarsteve From Sweden, joined Nov 2005, 3713 posts, RR: 34 Reply 39, posted (4 months 3 weeks 5 days 19 hours ago) and read 20525 times:
I was reading a presentation on the B787 at work, and there was one slide about batteries.
It showed that Yuasa also makes the batteries for the flight control computor. There are two of these batteries on board.
It also states that all these four Yuasa batteries are subject to IATA Dangerous Goods Regulations and cannot be carried on passenger aircraft as cargo.
So are these Flight Control batteries Lion as well?
Are they being investigated?
Just curios
I think anyone that has flown electric models knows that if one tries hard enough, one can make any sort of battery technology from any manufacturer to become unstable if they are not changed correctly.
I think it is a little early to point fingers at a particular battery manufacturer or battery technology, it is only one part of a larger system, it just happens to the most visible part that appears to have failed.
As you would know in flight the main and APU batteries should be receiving next to no change.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
CALTECH From Poland, joined May 2007, 1603 posts, RR: 22 Reply 41, posted (4 months 3 weeks 5 days 15 hours ago) and read 20320 times:
Quoting Tristarsteve (Reply 39): I was reading a presentation on the B787 at work, and there was one slide about batteries.
It showed that Yuasa also makes the batteries for the flight control computor. There are two of these batteries on board.
It also states that all these four Yuasa batteries are subject to IATA Dangerous Goods Regulations and cannot be carried on passenger aircraft as cargo.
So are these Flight Control batteries Lion as well?
Are they being investigated?
Just curios
Besides the Main and APU battery set, there are 3 sets of flight control emergency batteries. Haven't heard of any problems with these.
Quoting zeke (Reply 40): As you would know in flight the main and APU batteries should be receiving next to no change.
In normal flight, until you lose a engine or engine generators, then the batteries will receive a charge, especially after the APU starts up.
rcair1 From United States of America, joined Oct 2009, 950 posts, RR: 25 Reply 42, posted (4 months 3 weeks 5 days 13 hours ago) and read 20201 times:
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I'm reposting portions of a previous post that was removed because it quoted a post that quoted a post that quoted a post that was removed because that post violated rules. I actually don't know which was the offending post - but when a post is removed - every post that quotes it is removed - and if a post quotes one of the quoted ones, its removed- and so on.
It cascades - kind of like a Li-Ion Battery that has a cell in thermal runaway.
Sometimes it can be a lot of posts. In this case at least 16 posts were removed.
Reminds us all how important it is to follow the rules- I'm sure we lost some great discussions because of this - but I appreciate the mods trying to keep this thread focused.
I'm only posting the parts that I'm sure did not quote the post that quoted the offending post.
Quoting tdscanuck (Reply 37): In one of the bazillion posts buried in the CivAv theads, somebody stated that it was only the gases that were flammable (or electrolyte vapour, also a gas). However, I have no idea if that was accurate.
Tom - let me help you with that one.
In this post, in this thread - I discuss the findings in a 2011 study performed for the NFPA on the characteristics of Li-Ion rechargeable (secondary) cells.
Quoting rcair1 (Reply 26): In the 16850 cell - they estimated the cell contain 3-6 g of electrolyte (pp 89) but to be conservative, they base the calculations on 10g of electrolyte and 1.6g of poly based separator. Based on the heat of combustion for typical materials, they estimate that battery has ~280kJ in the material. The battery itself can contain between 25 and 40 kJ of energy - so the total energy content of the battery is on the order of 300-320 kJ.
Quoting rcair1 (Reply 26): Regarding flammability - not energy content - the report is less revealing. This is because the chemistry is so variable. What they do discuss is the flammability of vent gasses in terms of UFL and LFL - the range of concentrations where the vent gas is flammable. I refer you to the beginning of chapter 6 - PP 86.
According to tests at Sandia - the vent gases include H2, CO, CO2, CH4, C2H4, C2H6 and some others in vary small quantities. Of those gases - CO2 is the most prevalent - in the 65% range. C2H4 is next (15%ish) followed by CO and H2. CO2, of course, is not combustible - so the most prevalent gas in these test will act more like an extinguishing agent - by displacing O2 and dispersing the other vent gases.
H and CO have large flammability ranges (4-75% and 12.5 to 74%), CH4's pretty narrow (say 1.8 to 9% /-1) (pp87)
While both are flammable, it seems that vent gasses may pose the highest risk of ignition outside the containment because they must be allowed to escape. Whether or not that is a hazard - in the sense of the FAA understanding - I can't say. Vent gas fire would probably be hot, but short lived. It may re-kindle.
WingedMigrator From United States of America, joined Oct 2005, 2031 posts, RR: 56 Reply 43, posted (4 months 3 weeks 5 days 12 hours ago) and read 20187 times:
Ditto here... re-posting deleted stuff:
If we assume the underlying failure rate is constant, i.e. we are not dealing with an infant mortality issue
If we assume the battery system has accumulated 1.3 million hours of operation (as stated by Boeing exec)
Then:
With zero observed failures, the failure rate would have to be 2.3e-6 per hour (1 in 430,000 hours) to ensure there is only a 5% chance that they got lucky and saw "only" zero failures in 1.3 million hours.
With one observed failure, the failure rate would have to be 3.7e-6 per hour (1 in 270,000 hours) to ensure there is only a 5% chance that they got lucky and saw "only" one failure in 1.3 million hours.
With two observed failures, the failure rate would have to be 4.8e-6 per hour (1 in 208,000 hours) to ensure there is only a 5% chance that they got lucky and saw "only" two failures in 1.3 million hours.
Quoting tdscanuck: Do you think Poisson is the right distribution model to apply here? I know we don't know the underlying failure mechanism but I have a tough time thinking of any mechanism that would have a constant rate with time.
I agree that the current circumstances probably do not jive with the assumption of a constant failure rate. Subject to that (poor) assumption, and subject to one failure having occurred after 1.3 million battery hours, the odds of another failure within (50 airplanes x 2 batteries/airplane x 12 operating hours/battery/day x 2 days = 2400 hours) are roughly 1 in 125, based on a generously large failure rate that corresponds to 95% confidence level. That by itself is a red flag, a mathematical way of saying "lightning never strikes twice"... There's got to be something more than bad luck here.
The failure rate may not be constant in the same battery over time.
The failure rate may vary from battery to battery.
All that being said, the Poisson distribution is a fundamental building block of any reliability analysis. Without it, you cannot make the leap from discrete test outcomes to a calculated failure probability. There are surely more sophisticated versions of it that account for a variable failure rate, and no doubt powerful numerical simulation tools to synthesize all that, but then you have to guess what the failure rate curve looks like (the bathtub parameters). You can quickly find yourself grasping at unobservable straws.
If only these batteries didn't fail so damn rarely, we'd have better data to work with
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 44, posted (4 months 3 weeks 5 days 12 hours ago) and read 20196 times:
Quoting Tristarsteve (Reply 39): So are these Flight Control batteries Lion as well?
I think so. The use of Li-ion in small backup emergency batteries is pretty well established (the A380's been doing it without issue for many years). The ISS also uses them.
Not that I'm aware of. If they crack open *that* can of worms, it's going to impact a lot more than 787's...it will completely kill off flight deck iPads and laptops, for example.
Quoting WingedMigrator (Reply 43): If only these batteries didn't fail so damn rarely, we'd have better data to work with
zeke From Hong Kong, joined Dec 2006, 7770 posts, RR: 73 Reply 45, posted (4 months 3 weeks 5 days 12 hours ago) and read 20174 times:
Quoting CALTECH (Reply 41): In normal flight, until you lose a engine or engine generators, then the batteries will receive a charge, especially after the APU starts up.
In brand A aircraft I am only used to seeing batteries receiving a short charge in flight and then disconnecting from the charge (to bring the battery back up to its nominal voltage range). Most of the time they do not receive a charge, they are simply connected to the DC bus, however the DC bus is normally powered by normal power sources (AC BUS and TR to the DC BUS) and taking next to nothing from the batteries.
The 787 manual shows the 28 Vdc bus being normally powered by the 235 Vac bus via a power converter. I read the 787 FCOM on this part, it lacks any real depth to tell a lot of detail on the system. It does not show any input bus to charge the APU battery. I wonder if the main battery is continuously being charged, or if it has smarts in the system so it is only charged when required.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
PITingres From United States of America, joined Dec 2007, 966 posts, RR: 12 Reply 46, posted (4 months 3 weeks 5 days 11 hours ago) and read 20087 times:
I'll also repost my wild-eyed notion of using an aerogel within the containment case to enhance cell separation. The stuff is supposed to be an excellent insulator, is lightweight and heat resistant, and an extremely poor heat conductor. You could probably cast some sort of vent baffling into it for venting isolation. I don't know if an aerogel is or can be made corrosion resistant, though, and I don't know how well it withstands shock and vibration.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 48, posted (4 months 3 weeks 5 days 10 hours ago) and read 20049 times:
Quoting Pihero (Reply 47): Anybody has gen on the NTSB press conference that was supposed to happen @ 0230pm est ?
Looks to still be planned to start in 10 minutes. There does not appear to be a public-facing option to follow in real-time - no webcast and CSPAN/CSPAN2 are not carrying it. There is a teleconference line, but you must RSVP and it appears to be limited to the press.
BoeEngr From United States of America, joined Feb 2010, 315 posts, RR: 33 Reply 50, posted (4 months 3 weeks 5 days 10 hours ago) and read 20015 times:
Quoting Stitch (Reply 48): Looks to still be planned to start in 10 minutes. There does not appear to be a public-facing option to follow in real-time - no webcast and CSPAN/CSPAN2 are not carrying it. There is a teleconference line, but you must RSVP and it appears to be limited to the press.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 51, posted (4 months 3 weeks 5 days 9 hours ago) and read 19985 times:
Thanks. I came in at the tail-end of the Q&A session, but I heard the spokeswoman noting there was a thermal runaway and short-circuiting inside the battery. The Chicago Sun-Times reported that federal officials found that all eight cells in the APU battery on the JL frame exhibited thermal damage.
BoeEngr From United States of America, joined Feb 2010, 315 posts, RR: 33 Reply 52, posted (4 months 3 weeks 5 days 9 hours ago) and read 20005 times:
Quoting Stitch (Reply 51): Quoting BoeEngr (Reply 50):
It's currently live on NBC:
Thanks. I came in at the tail-end of the Q&A session, but I heard the spokeswoman noting there was a thermal runaway and short-circuiting inside the battery. The Chicago Sun-Times reported that federal officials found that all eight cells in the APU battery on the JL frame exhibited thermal damage.
I didn't find it overly informative. She confirmed they have, to this date, ruled nothing out, and re-affirmed (multiple times) that they are investigating because they would not expect two battery incidents to occur within a two week period. She noted they will be reviewing whether anything was missed in the certification process, and see if changes need to be made.
She also stated that the JAL incident is being considered a "fire event", but that the NH incident is currently considered a "smoke event", not fire.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 53, posted (4 months 3 weeks 5 days 9 hours ago) and read 20004 times:
Thank you.
Reuters is reporting the NTSB chairman stated the systems designed to prevent a battery fire aboard a 787 did not work as intended. Did she provide any specifics?
BoeEngr From United States of America, joined Feb 2010, 315 posts, RR: 33 Reply 55, posted (4 months 3 weeks 5 days 9 hours ago) and read 19969 times:
My interpretation was simply a statement that it shouldn't have caught fire, but it did, so the preventative measures didn't work. When asked for specifics, she stated "things like battery monitoring". That's how I recall it, anyway. Hopefully there will be a transcript.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 56, posted (4 months 3 weeks 5 days 9 hours ago) and read 19994 times:
Thanks again.
The Seattle Times just posted an article on the press conference and the details announced.
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 57, posted (4 months 3 weeks 5 days 8 hours ago) and read 19909 times:
Quoting Stitch (Reply 51): Thanks. I came in at the tail-end of the Q&A session, but I heard the spokeswoman noting there was a thermal runaway and short-circuiting inside the battery. The Chicago Sun-Times reported that federal officials found that all eight cells in the APU battery on the JL frame exhibited thermal damage.
Would not short circuiting fall under the category of "manufacturing defect?" I know that in laptop batteries, there are fuses (tiny pieces of metal) that are designed to melt away if a short happens. The battery pack needs replacement if the fuse ever gets blown...but the idea is that the fuse blows before you get a thermal runaway on a LiIon battery.
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
Pihero From France, joined Jan 2005, 3598 posts, RR: 72 Reply 58, posted (4 months 3 weeks 5 days 8 hours ago) and read 19916 times:
Thanks for the link, Stitch.
The picture of the aft electronic bay is quite impressive.
Basically nothing new for another week, iF I understand correctly.
It also seems that they refuise to lump both events into one - just one - chain of events..
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 59, posted (4 months 3 weeks 5 days 8 hours ago) and read 19905 times:
I'm thinking that in the JL incident, sitting on the ground might have contributed to the problem. Seems like the systems designed to ventilate smoke and heat from the E&E bays require 1) the aircraft to be fully on, and 2) a pressure differential to exist betwen the E&E bay and the outside world, with the E&E bay pressure being greater
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
Tristarsteve From Sweden, joined Nov 2005, 3713 posts, RR: 34 Reply 60, posted (4 months 3 weeks 5 days 8 hours ago) and read 19885 times:
Quoting zeke (Reply 45): The 787 manual shows the 28 Vdc bus being normally powered by the 235 Vac bus via a power converter. I read the 787 FCOM on this part, it lacks any real depth to tell a lot of detail on the system. It does not show any input bus to charge the APU battery. I wonder if the main battery is continuously being charged, or if it has smarts in the system so it is only charged when required.
Just been looking at a B787 Schematics manual. There are too many abbreviations!, but
The Main battery is connected to a Hot battery bus. This is charged by a Battery Charger normaly fed by the Capt Instrument Bus which gets its power from 28V DC1. In normal operation the battery only powers the Hot battery Bus which has tiny loads on it.
The APU battery is connected to the APU Hot battery bus. This is charged by the APU Battery charger which gets power from the F/O Instrument bus which is normaly supplied by 28V DC C2.
Caveat. I have had no training on the aircraft, and it is very different to the B777 at this level.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 61, posted (4 months 3 weeks 5 days 7 hours ago) and read 19852 times:
Quoting KELPkid (Reply 59): I'm thinking that in the JL incident, sitting on the ground might have contributed to the problem.
That was *the* reason there was smoke on the main deck. None of the smoke containment features will work properly with the ECS off and sitting on the ground. The EE bay cooling fans will still run if the aircraft is powered up but, by themselves, they're not going to do the whole job.
kanban From United States of America, joined Jan 2008, 2500 posts, RR: 21 Reply 62, posted (4 months 3 weeks 5 days 4 hours ago) and read 19639 times:
While we've all heard or read the words from the press conf. here are some interesting pictures of the disassembly.. I think picture three has the second battery of the same plane disassembled in the background.. (I could be wrong)
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 63, posted (4 months 3 weeks 4 days 16 hours ago) and read 19312 times:
"Circuit boards that control and monitor the performance of the plane's lithium-ion battery unit were charred and may be of little use to the teams investigating why the battery effectively melted"
Not surprising. The charge controller is a small circuit board which is integral to the battery. It is not the same thing as the battery charger itself, which is a separate box directly next to the battery.
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 65, posted (4 months 3 weeks 4 days 12 hours ago) and read 19127 times:
Quoting CM (Reply 65): Not surprising. The charge controller is a small circuit board which is integral to the battery. It is not the same thing as the battery charger itself, which is a separate box directly next to the battery.
Got it. That was probably the part that tracked status of individual cells then. If it had quit first, I'd have expected the system to default to a lower maintenance voltage, like 29.5 to 30 volts.
Any idea if they're intelligent and monitored by the charger, or just simple thermistor like devices to reduce charge current to warm cells?
kanban From United States of America, joined Jan 2008, 2500 posts, RR: 21 Reply 66, posted (4 months 3 weeks 4 days 12 hours ago) and read 19086 times:
Aviation Herald has some new pictures including a hole in an electrode
Kaiarahi From Canada, joined Jul 2009, 2587 posts, RR: 24 Reply 68, posted (4 months 3 weeks 3 days 11 hours ago) and read 18598 times:
There's also a new NTSB twitter update: "The battery charging unit passed all significant tests and no anomalies were detected."
So far we have:
- evidence of an internal short (damaged electrode)
- BCU appears to operate correctly (assuming there is no test design deficiency)
- limited information obtainable from the 2 internal circuit boards (which presumably control individual cell charging/monitoring)
So it *seems* (at least to my legal evidentiary mind) that the evidence is pointing towards one or a combination of:
- a cell manufacturing defect (electrode shorting because of improper manufacturing tolerances / FOD is a known cause of Li-Ion failures)
- an internal circuit board design or manufacturing defect.
Pihero From France, joined Jan 2005, 3598 posts, RR: 72 Reply 69, posted (4 months 3 weeks 3 days 8 hours ago) and read 18480 times:
Thanks for these posts, Kaiarahi.
My git feelein has always been on manufacturing defects and / or quality control of the battery manufacurer.
That doesn't change the fact that the protection circuit should have worked as specs (but are we still in the realm of original specifications ? ).
Or am I way out of base ?
Quote: We need to keep in mind that these safety precautions are only effective if the mode of operation comes from the outside, such as with an electrical short or a faulty charger. Under normal circumstances, a lithium-ion battery will simply power down when a short circuit occurs. If, however, a defect is inherent to the electrochemical cell, such as in contamination caused by microscopic metal particles, this anomaly will go undetected. Nor can the safety circuit stop the disintegration once the cell is in thermal runaway mode. Nothing can stop it once triggered
KC135Hydraulics From United States of America, joined Nov 2012, 165 posts, RR: 0 Reply 71, posted (4 months 3 weeks 3 days 7 hours ago) and read 18455 times:
So are we saying that the NTSB may be incorrect in stating that Boeing's protection systems did not work correctly? What I've been reading in the last couple posts, is that if there is an internal defect with the battery, the protection systems are incapable of working to stop the battery from catching fire. If this is the case, then Boeing's systems are adequate to protect a properly manufactured battery but not an incorrectly manufactured battery. Is there any protection system available that can prevent a thermal runaway event in a defective battery? I'm assuming there is not, and in that case then the heat can and should be lifted from Boeing relatively soon.
kanban From United States of America, joined Jan 2008, 2500 posts, RR: 21 Reply 72, posted (4 months 3 weeks 3 days 4 hours ago) and read 18358 times:
Quoting KC135Hydraulics (Reply 71): What I've been reading in the last couple posts, is that if there is an internal defect with the battery, the protection systems are incapable of working to stop the battery from catching fire.
That's the way it sounds to me.. And I'm not sure how one would design a protection system that would preclude the failure from an internal defect.
Reading through the NTSB slide show, I can see why a runaway has a very limited duration.. there's just not enough material there.. It's looking like an improved (meaning slightly larger) containment box above a new drip shield/pan. One concern about a larger containment box though is would it provide more combustion room and defeat the purpose. So is it possible to quarter the battery box with double insulated steel walls and have only two cells in each space and still get the benefits out of the unit?
I wonder about ducting to the outside if the electrolyte and gasses are low temperature flammable.. In air probably no problem, but on the ground as the JAL was, what are the possibilities of igniting the CFRP?
The other thing I've been thinking about would be adding either closed circuit cameras continually watching the batteries, or ones that could be turned on and record whenever transient particular matter reached a predetermined threshold. I wouldn't expect these to become long term installations, but just another tool if there is another failure after the fleet is flying again.
Pihero From France, joined Jan 2005, 3598 posts, RR: 72 Reply 73, posted (4 months 3 weeks 3 days 4 hours ago) and read 18338 times:
Quoting KC135Hydraulics (Reply 71): . Is there any protection system available that can prevent a thermal runaway event in a defective battery? I'm assuming there is not, and in that case then the heat can and should be lifted from Boeing relatively soon.
I really do not think that would be acceptable for any certifying authorityhowever dearly we would like to see the planes back in the air where they belong.To the contrary : a protection system that fails in 4% of the fleet (two airplanes out of fifty ) is way short of what we call acceptable risk levels.
That's why I posed the question on whether we're still in the realm of the original specifications.
Tom should provide more qualified opinion on this subject. I'm just an operator ( and even then, not of the 787 ).
WingedMigrator From United States of America, joined Oct 2005, 2031 posts, RR: 56 Reply 74, posted (4 months 3 weeks 3 days 3 hours ago) and read 18311 times:
Quoting kanban (Reply 72): So is it possible to quarter the battery box with double insulated steel walls and have only two cells in each space and still get the benefits out of the unit?
I'm not sure if that helps... all it would do for you is reduce the size of the fire, and maybe provide battery function during and after the fire. But you've still had a fire. It's the same response, both for immediate measures to ensure everyone's safety, and for the regulatory / public relations mess. So what problem were you solving?
Quoting kanban (Reply 72): what are the possibilities of igniting the CFRP?
I'm curious about this too. How flammable is CFRP? Epoxy resin seems like a pretty good fuel, at least compared to aluminum...
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 75, posted (4 months 3 weeks 3 days 3 hours ago) and read 18306 times:
Thanks for finding that Kaiarahi. It answers just about all the questions I had about the design.
Packing the cells like that surprises me a little, given the nature of Lithium batteries. An extra 20 pounds of steel and 2 inches of space should let them come up with a segmented design that would isolate the cells from each other. I'm not in aviation, other than communications, but in my business we'd want to keep whatever happened from happening again, and make sure that it would be handled better if it did happen.
I'm guessing that a bunch new cells and cells from the same batch as the troublemakers are being dissected and analyzed to check for manufacturing issues.
Kaiarahi From Canada, joined Jul 2009, 2587 posts, RR: 24 Reply 76, posted (4 months 3 weeks 3 days 3 hours ago) and read 18305 times:
Quoting nomadd22 (Reply 75): Thanks for finding that Kaiarahi. It answers just about all the questions I had about the design.
Packing the cells like that surprises me a little, given the nature of Lithium batteries.
My first thoughts around the packing are that Li-Ion is mostly used (and designed) for consumer electronic applications, where space is at a premium. Perhaps there's a paradigm shift that needs to happen here, where the battery engineers are not fixated on minimizing physical space.
I can't say much more, but my eldest son is an exec at Yuasa ....
Seat55A From New Zealand, joined Jan 2013, 31 posts, RR: 0 Reply 77, posted (4 months 3 weeks 3 days 3 hours ago) and read 18379 times:
Quoting kanban (Reply 72): I'm not sure how one would design a protection system that would preclude the failure from an internal defect.
I think one must expand the scope of thinking about fault protection, to include the Quality Control (and production quality engineering) of the cells and the battery assembly. I mean, the chance that a defect can pass through those processes must be part of the fault probability calculation for the airplane as a whole system.
Quoting nomadd22 (Reply 75): I'm guessing that a bunch new cells and cells from the same batch as the troublemakers are being dissected and analyzed to check for manufacturing issues.
Yes, and suppose an issue is found (with one or more batches), would it not be necessary to explain why the issue is limited to those batches and how it got through? Until they could do so, wouldn't all the production be equally suspect? It would be a big step in understanding for sure, but wouldn't make everything O.K.
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 78, posted (4 months 3 weeks 2 days 22 hours ago) and read 18260 times:
Quoting WingedMigrator (Reply 74):
I'm curious about this too. How flammable is CFRP? Epoxy resin seems like a pretty good fuel, at least compared to aluminum...
Aluminum is most assuredly flammable. You haven't thrown beer cans into the camp fire?
Granted, it doesn't go up like magnesium in your high school chemistry class...but it does burn. Aluminum was a key ingredient in the Space Shuttle Solid Rocket Booster propellant....
[Edited 2013-01-26 23:48:07]
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
Deltal1011man From United States of America, joined Sep 2005, 8628 posts, RR: 8 Reply 79, posted (4 months 3 weeks 2 days 19 hours ago) and read 18178 times:
Just got to say thanks to CM for starting a thread that isn't full of trolls.
Quoting CM (Reply 18): Not to create a theme, but Would you believe you can get both mechanical and aero degrees with nothing more than grade 10 chemistry? I hated it, did poorly in it, and retained none of it. I will truly be of no use to you on topics of chemistry.
Ha!
Or, say never mind to those degrees, go and get and A&P and a business degree and just go into management (and never, ever have to take a Chemistry class(even in HS). Math = good, Chemistry....run, run as fast as you can!)
Quoting KC135Hydraulics (Reply 21): Much prefer the discussion on this forum than on civil aviation! I also posted this picture there, but I thought it'd be interesting for conversation here. These are the batteries on the KC-135. They are lead-acid, 28v. These are kept in the latrine... as you can see, the toilet on the left and the urinal can to the right.
Whoa. Could make for a crappy day if the you hit some kind of chop.... (pun intended)
Quoting moose135 (Reply 27): If it even got to that point, I suspect Boeing might eat some (or most) of the cost of repairs simply to avoid the PR issue of having a 787 written off at this stage of the game.
Agree. I don't see Boeing letting this bird get scraped unless it is reeeeeally bad off.
Quoting moose135 (Reply 27): And it was never that bright in there. Aim carefully!
no kidding.
"Oh look at the sUGAr falling out of the sky! Look at the sUGAr falling out of the sky!" LM 1922-2011 Go Dawgs! G.A.T.A.
sunrisevalley From Canada, joined Jul 2004, 4002 posts, RR: 4 Reply 80, posted (4 months 3 weeks 2 days 17 hours ago) and read 18109 times:
Am I correct in my understanding that in the two incidents in question ( JL and ANA) the batteries had relatively low "hours" and that there are other batteries in service with many more hours on them.
Does it make sense to take each new battery and run it through charge/discharge cycles for "X" hours to take care of the possibility of a manufacturing fault. Perhaps the testing process should require the battery to be able to cope with abnormal loads , say somewhere between 3 and 10% .
My worth
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 81, posted (4 months 3 weeks 2 days 13 hours ago) and read 17992 times:
Quoting sunrisevalley (Reply 80): Am I correct in my understanding that in the two incidents in question ( JL and ANA) the batteries had relatively low "hours" and that there are other batteries in service with many more hours on them.
The Ship's Battery on the NH bird was replaced in October. The airframe was delivered in January 2012, so that would make the original battery upwards of 10 months old. The APU battery on that frame would be 12 months old.
JA801A, NH's first delivery, is 17 months old. JA802A is 16 months old and JA805A is 13 months old. If they have their original delivery batteries, then they will be at least that old.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 82, posted (4 months 3 weeks 2 days 8 hours ago) and read 17773 times:
Quoting kanban (Reply 72): I wonder about ducting to the outside if the electrolyte and gasses are low temperature flammable.. In air probably no problem, but on the ground as the JAL was, what are the possibilities of igniting the CFRP?
Quoting WingedMigrator (Reply 74): I'm curious about this too. How flammable is CFRP? Epoxy resin seems like a pretty good fuel, at least compared to aluminum...
Although not totally inflammable, CFRP doesn't burn as well as aluminum. It's harder to light and takes longer to burn through. In virtually ever conceivable fire situation, CFRP is better to have around.
Quoting Pihero (Reply 73): That's why I posed the question on whether we're still in the realm of the original specifications.
Tom should provide more qualified opinion on this subject.
The original specifications would be contained in something called a Specification Control Document (SCD) that goes from Boeing to the supplier an defines everything in nauseating detail (these things are hundreds of pages for even very simple components...for a battery it would be huge). I do not know if we're in the range of the SCD or not; even if I had the document it would be highly proprietary.
Quoting WingedMigrator (Reply 74): I'm not sure if that helps... all it would do for you is reduce the size of the fire, and maybe provide battery function during and after the fire. But you've still had a fire.
That's never going to go away. They'll have to convince the FAA/NTSB that they've pushed the probability of a fire down (by identifiying and fixing whatever caused these two fires) *and* convince them you have the fire properly contained.
Quoting sunrisevalley (Reply 80): Does it make sense to take each new battery and run it through charge/discharge cycles for "X" hours to take care of the possibility of a manufacturing fault.
Quoting sunrisevalley (Reply 80): Perhaps the testing process should require the battery to be able to cope with abnormal loads , say somewhere between 3 and 10% .
I'd be appalled if this wasn't already part of the manufacturing procedure. It's too obvious to not be.
Seat55A From New Zealand, joined Jan 2013, 31 posts, RR: 0 Reply 83, posted (4 months 3 weeks 2 days 7 hours ago) and read 17686 times:
Quoting sunrisevalley (Reply 80): Does it make sense to take each new battery and run it through charge/discharge cycles for "X" hours to take care of the possibility of a manufacturing fault.
Is extended quality testing of 100% of articles really normal for any manufacturing process? That's far more than Quality Control. It expresses zero confidence in the quality aspects of the manufacturing process. I don't see how the morale of the company could survive this. I wonder also about marketability of the products where the company itself has this low level of confidence in its processes. I am certainly not an expert in manufacturing Q C and happy to be told I'm wrong.
If the incidents were due to failure of batteries that did undergo such extended testing (if the cause of the fault is the batteries), that's not too good for return to flight.
zanl188 From United States of America, joined Oct 2006, 3261 posts, RR: 0 Reply 84, posted (4 months 3 weeks 2 days 5 hours ago) and read 17615 times:
Todays NTSB update:
January 27, 2013
WASHINGTON – The National Transportation Safety Board today released a fourth update on its investigation into the Jan. 7 fire aboard a Japan Airlines Boeing 787 at Logan International Airport in Boston. The fire occurred after the airplane had landed and no passengers or crew were onboard.
The event airplane, JA829J was delivered to JAL on December 20, 2012. At the time of the battery fire, the aircraft had logged 169 flight hours with 22 cycles. The auxiliary power unit battery was manufactured by GS Yuasa in September 2012.
NTSB investigators have continued disassembling the internal components of the APU battery in its Materials Laboratory in Washington, and disassembly of the last of eight cells has begun. Examinations of the cell elements with a scanning-electron microscope and energy-dispersive spectroscopy are ongoing.
A cursory comparative exam has been conducted on the undamaged main battery. No obvious anomalies were found. More detailed examination will be conducted as the main battery undergoes a thorough tear down and test sequence series of non-destructive examinations.
In addition to the activities at the NTSB lab, members of the investigative team continue working in Seattle and Japan and have completed work in Arizona. Their activities are detailed below.
ARIZONA
The airworthiness group completed testing of the APU start power unit at Securaplane in Tucson and the APU controller at UTC Aerospace Systems in Phoenix. Both units operated normally with no significant findings.
SEATTLE
Two additional NTSB investigators were sent to Seattle to take part in FAA’s comprehensive review. One of the investigators will focus on testing efforts associated with Boeing's root cause corrective action efforts, which FAA is helping to lead. The other will take part in the FAA's ongoing review of the battery and battery system special conditions compliance documentation.
JAPAN
The NTSB-led team completed component examination of the JAL APU battery monitoring unit at Kanto Aircraft Instrument Company, Ltd., in Fujisawa, Kanagawa, Japan. The team cleaned and examined both battery monitoring unit circuit boards, which were housed in the APU battery case. The circuit boards were damaged, which limited the information that could be obtained from tests, however the team found no significant discoveries.
Additional information on the NTSB’s investigation of the Japan Airlines B-787 battery fire in Boston can be found at http://go.usa.gov/4K4J
The NTSB will provide another factual update on Tuesday, Jan. 29, or earlier if developments warrant. To be alerted to any updates or developments, follow the NTSB on Twitter at www.twitter.com/ntsb
#NTSB#
[Edited 2013-01-27 16:19:01]
Legal considerations provided by: Dewey, Cheatum, and Howe
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 85, posted (4 months 3 weeks 2 days 5 hours ago) and read 17584 times:
Quoting Seat55A (Reply 83): Is extended quality testing of 100% of articles really normal for any manufacturing process?
For safety critical applications, it's absolutely normal.
Quoting Seat55A (Reply 83): That's far more than Quality Control. It expresses zero confidence in the quality aspects of the manufacturing process.
No. It's the reality that complicated assemblies with hundreds or thousands of components have no realistic chance of achieving acceptable reliability through statistical control, even if the individual process are really good. The chance that one of your thousands of parts is bad is too high. If you need 100% pass, you do 100% inspection. Anything less will *always* allow something through, albeit at potentially very low rate. For many types of goods, the potential of a bad unit getting through is just economic and you roll it into the cost of doing business. That's not generally an acceptable practice where a faulty unit could kill someone. Even something as mundane as pre-filled syringes (for vaccines and such) that can be manufactured in the millions and only have four or five parts are 100% inspected.
Quoting Seat55A (Reply 83): I don't see how the morale of the company could survive this. I wonder also about marketability of the products where the company itself has this low level of confidence in its processes.
It has nothing to do with low confidence. Suppose you've got a 6-sigma process (which almost nobody in aerospace has because their volumes are too low) on every single part you use and your assembly has 1000 parts. There is a 4 per million chance that any *one* of the parts is bad. There is a 4000 per million (0.1%) chance that your assembly is bad due to a single bad part even with absolutely top-notch process confidence, and that's not counting potential errors in all the assembly steps. In the real world, you've got redundancy and part failures aren't independent and other stuff, but the point still stands. Once you have very complicated products and you don't accept defects, you can't rely on process alone with any level of confidence.
Seat55A From New Zealand, joined Jan 2013, 31 posts, RR: 0 Reply 86, posted (4 months 3 weeks 2 days 4 hours ago) and read 17535 times:
Quoting zanl188 (Reply 84):
Todays NTSB update:
. . . .
January 27, 2013
SEATTLE
Two additional NTSB investigators were sent to Seattle to take part in FAA’s comprehensive review. One of the investigators will focus on testing efforts associated with Boeing's root cause corrective action efforts,
Is this code for "Boeing has a proposed fix and they need people to try and break it"?
Kaiarahi From Canada, joined Jul 2009, 2587 posts, RR: 24 Reply 87, posted (4 months 3 weeks 2 days 3 hours ago) and read 17507 times:
Quoting zanl188 (Reply 84): The NTSB-led team completed component examination of the JAL APU battery monitoring unit at Kanto Aircraft Instrument Company, Ltd., in Fujisawa, Kanagawa, Japan. The team cleaned and examined both battery monitoring unit circuit boards, which were housed in the APU battery case. The circuit boards were damaged, which limited the information that could be obtained from tests, however the team found no significant discoveries.
Sounds to me that it's getting closer and closer to cell manufacturing defects (cue the shorted electrode), which are the cause of the majority of Li-Ion failures (rcair1 cited a study, which I can't find anymore on the civav compost heap). So far, the charger (Securaplane) and the monitoring boards (Kanto) *seem* to be OK.
My source at Yuasa suggests that they're reviewing QA processes and working on designing better isolation of cells so that thermal runaway does not propagate. In a sense, the latter is containment - within the battery itself, rather than containing the whole unit.
HAWK21M From India, joined Jan 2001, 31228 posts, RR: 58 Reply 88, posted (4 months 3 weeks 1 day 23 hours ago) and read 17379 times:
Anyone having the list of snags till date on the type.
One Engine issue during test conditions.
One Electrical fire during test conditions that was alleged attributed to a forgotton tool .....
These couple of thermal runways last few days.
KC135Hydraulics From United States of America, joined Nov 2012, 165 posts, RR: 0 Reply 89, posted (4 months 3 weeks 1 day 20 hours ago) and read 17305 times:
Quite a few generator failures in flight as well Hawk. Definitely on United and Qatar airlines, maybe others too.
canoecarrier From United States of America, joined Feb 2004, 2671 posts, RR: 12 Reply 91, posted (4 months 3 weeks 1 day 10 hours ago) and read 16941 times:
Good discussion here. I won't add much to the discussion and won't post other than this but as Kaiarahi mentioned the Civ-Av threads have become a septic tank so to say.
The Seattle Times is reporting that the NTSB has cleared the battery charger of any faults in the Boston incident and that Japanese investigators have shifted their investigation from the battery manufacturer (Yuasa) to the the manufacturer of the battery monitoring system (Kanto).
I provided this link a week ago in the a.net GA forum. Maybe it made its way to Twitter from there???
Page #13 is interesting, especially:
- Independence of cells / cooling areas between cells
- Venting areas within the battery
- Specific venting outside the battery/aircraft when relevant
If this Airbus safety conference had taken place today, and not almost a year ago, then these things would have created a lot of questions from the audience.
But Airbus is silent today. I understand that.
But last week an Airbus spokesman (not JL) did comment hard pressed by Reuters. He said that the A350 containment system was more robust, and they believe it would pass certification without issues. But in case certification conditions got changed, then the A350 would be modified accordingly, which would involve a potential delay depending on the circumstances.
Always keep your number of landings equal to your number of take-offs, Preben Norholm
okie From United States of America, joined Jul 2003, 2410 posts, RR: 3 Reply 95, posted (4 months 3 weeks 14 hours ago) and read 16278 times:
Lots of obvious things keep popping up that one would assume would be addressed long before now.
There are a lot of systems on the 87 that are powered with VFD's which are notorious bad neighbors.
I do not know the architecture of the system or if they use 6, 12 or 18 pulse drives.
What I would say, if you would try to sell me that a high emf harmonic generated by one of the VFD's of a half wave was introduced to the AC bus at the same time the SCR of the battery charger was firing and it damaged the separator of a battery cell then I would sure listen.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 96, posted (4 months 3 weeks 13 hours ago) and read 16262 times:
Quoting okie (Reply 95): There are a lot of systems on the 87 that are powered with VFD's which are notorious bad neighbors.
I do not know the architecture of the system or if they use 6, 12 or 18 pulse drives.
The VFD's "hide" behind the high voltage DC buses. The HVDC buses feed motor controllers that change the DC into appropriate frequency/voltage AC to run the VFD's. The pipe from the motor controllers to the VFD's is dedicated to each VFD. I don't think there's any way for interference to propagate back upstream to the DC side, which is where it would have to go to (eventually) get back into the 28VDC or 115VAC buses that run all the avionics.
okie From United States of America, joined Jul 2003, 2410 posts, RR: 3 Reply 97, posted (4 months 3 weeks 13 hours ago) and read 16216 times:
Quoting tdscanuck (Reply 96):
The VFD's "hide" behind the high voltage DC buses
Yes, I know, something I deal with everyday but larger drives with multiple 3,000+ amp DC busses.
We deal with the harmonics issue with phasing transformers (12 & 18 pulse) and as well as line reactors on the AC supply side for the DC buss to attinuate the harmonics.
I would doubt that an aircraft would take that kind of a weight penalty but again I do not know the architecture of the system.
KC135Hydraulics From United States of America, joined Nov 2012, 165 posts, RR: 0 Reply 98, posted (4 months 3 weeks 10 hours ago) and read 16019 times:
Varible Frequency Drive.
Used to control speed and torque of a three phase electric motor. There are some exotic 5 and 11 phase out there but not involved here I believe.
Used on the Air Con packs and some hydraulics on the 87 (others I am sure)
A VERY simple explanation would be in the case an air con pack would be that you slow the device down or speed it up in relation demand on the system, saving energy vs the previous applications of running the packs full speed all the time and control with bypass and out flow. Same with a hydraulic pump it just creeps along with nothing going on in the system then speeds up when some hydraulic demand is required.
Seat55A From New Zealand, joined Jan 2013, 31 posts, RR: 0 Reply 101, posted (4 months 3 weeks 8 hours ago) and read 15901 times:
Thinking about dirty power as a source of problems, do we know if the ground power sources and procedures have been checked out? One of the incidents was on the ground, and the other manifested quite shortly after takeoff and could have been triggered on the ground.
mham001 From United States of America, joined Feb 2005, 3017 posts, RR: 2 Reply 102, posted (4 months 3 weeks 5 hours ago) and read 15890 times:
Quoting okie (Reply 95): What I would say, if you would try to sell me that a high emf harmonic generated by one of the VFD's of a half wave was introduced to the AC bus at the same time the SCR of the battery charger was firing and it damaged the separator of a battery cell then I would sure listen.
What reaction could the charger have that would damage the separator without the BMS recording the event or being damaged itself?
in the EV world, it is BMS that cause most of the battery problems. If there is anything that needs to be changed on the 787 IMO, it is the absurdity of having the BMS in the same small box as the batteries. And they went to the trouble of designing in two cooling fans, for what, the batteries or the electronics, is unclear. Another thing this design insures besides the obvious is the additional expense of replacing the BMS every time the battery is replaced.
I am all for the development and use of lithium batteries but there are some simple common sense protocols that should be followed, especially in aviation use. One of those is to keep the electronics controlling the batteries away from them. IMO.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 103, posted (4 months 3 weeks 4 hours ago) and read 15869 times:
Quoting mham001 (Reply 102): I am all for the development and use of lithium batteries but there are some simple common sense protocols that should be followed, especially in aviation use. One of those is to keep the electronics controlling the batteries away from them. IMO.
You're really not going to like where they locate the engine computers...
okie From United States of America, joined Jul 2003, 2410 posts, RR: 3 Reply 104, posted (4 months 3 weeks 4 hours ago) and read 15841 times:
Quoting mham001 (Reply 102): What reaction could the charger have that would damage the separator without the BMS recording the event?
That is my point, if the SCR in the charger was firing it lets anything through as its gate signal firing angle is calculated off the end of the previous sine wave.
The BMS is not a recording oscilloscope, it would never see such a short event.
The separator between the Al & Cu plates is very thin, I have no idea its dielectric strength but if it is damaged then the short would feed on its self and a BMS mounted in the battery would absolutely be useless except to be more fuel for the fire.
I think the problem will be found. The solution may be as simple as increasing the dielectric separator thickness .0001 inch and take a 3% hit on the battery output and gain a few ounces of weight.
JHwk From United States of America, joined Jan 2013, 39 posts, RR: 0 Reply 105, posted (4 months 3 weeks 3 hours ago) and read 15827 times:
Been reading up and finally broke down and joined to post a question/comment. Really appreciate all the information people have shared and it is nice to have found this thread rather than the CivAv one. My background is stationary power systems, and I have never dealt with Li-Ion batteries in that capacity but do deal with significant lead-acid battery systems and power electronics.
The first thing that (so far) has surprised me is the apparently limited information from the battery management system. I would have assumed in a system like this that near-real time impedance monitoring of each cell is provided for early warning. Temperature is a lagging indicator of thermal runaway, but cell impedance should give a solid idea of a developing problem. I would imagine the first priority is limiting the destruction of the battery, but also to ensure that the battery is available when required.
Regarding Okie's theory on the VFDs, my curiosity was actually the rectifier end of the system first (variable voltage variable frequency power converters?)-- Are those IGBT or SCR based systems? The development timeline would suggest SCR is possible, but IGBT would be a much more "clean" system. Likewise, the variable frequency drives-- are they IGBT or SCR based? Harmonics problems could explain some of the generator failures, and AC ripple current on the DC bus is known to damage batteries, but I would have expected that type of thing to filter out during testing and early flight hours. I assume the battery charger is filtering out the charge current, but the battery is not isolated from the bus until needed from the terms I keep hearing-- likely just blocking diodes.
Anyway, best wishes to the Boeing folks and the investigators to getting things resolved soon. Any information is appreciated.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 106, posted (4 months 3 weeks 3 hours ago) and read 15829 times:
Quoting okie (Reply 104): That is my point, if the SCR in the charger was firing it lets anything through as its gate signal firing angle is calculated off the end of the previous sine wave.
The battery chargers run off the 28VDC buses...I'm not an electrical guy but I can't see any reason the chargers would have SCRs. If the chargers are getting bad power it's got to be coming down the pipe from the transformer/rectifiers that feed the 28VDC buses.
The basic 787 power flow is:
Generators produce 230V wild frequency AC
-Transformer/rectifiers change this to 28VDC to power the DC loads, including the battery chargers
-Transformers change this to 115VAC (still wild frequency) to power the medium size AC loads
-Transform/rectifiers change this to +-270VDC to power the large motor controllers
---270VDC is changed to variable V variable F AC to power the large motors
Quoting JHwk (Reply 105): Been reading up and finally broke down and joined to post a question/comment.
JoeCanuck From Canada, joined Dec 2005, 5135 posts, RR: 29 Reply 108, posted (4 months 2 weeks 6 days 22 hours ago) and read 15683 times:
Excellent thread...kudos all...keep it coming.
There is a possibility that no precise cause of the fires will ever be found, or that the two fires were initiated differently. What are the likely available options? Would greater containment ever be enough to get these batteries re-certified, if no initiating cause was ever discovered? Or, would the regulators be more likely to demand an all new battery?
So basically, if no absolute or common initiating event is found...then what?
Obviously educated guesswork would be involved but there are a lot of educated guessers in here. Thanks.
Quoting Deltal1011man (Reply 79): Math = good, Chemistry....run, run as fast as you can!
A niece graduated chemical engineering last year...we worry about her.
AirlineCritic From Finland, joined Mar 2009, 623 posts, RR: 1 Reply 109, posted (4 months 2 weeks 6 days 22 hours ago) and read 15672 times:
There was always (at least) two parts in the concern. The frequency of the events, and their treatment.
Given that they now are saying multiple batteries were being replaced in Japan in a small fleet of aircraft, I am hopeful that a manufacturing, charging system, or other reason will be found behind the events. This was no freak occurrence, it was a real problem. Of course, I could be wrong...
But the treatment, including containment is an independent manner, and improved solutions can easily be demonstrated, even if no initial cause for the events is found.
In the unlikely case of not finding the smoking bat^H^H^Hgun for the failures, I would still guess that a combination of sufficient statistical testing of the batteries and the new containment design would be enough for the flights to continue. However, it is probably (much) faster to find the initial cause than to do a lot of testing and perhaps even flying to prove the batteries are statistically safe.
JoeCanuck From Canada, joined Dec 2005, 5135 posts, RR: 29 Reply 110, posted (4 months 2 weeks 6 days 20 hours ago) and read 15642 times:
Quoting Stitch (Reply 11): There is a drawing of the forward and aft EE bays at the start of this PPrune thread, but I do not know how accurate they are. If the drawing is accurate to scale, then it looks like there may be room around it.
Here's something I found especially interesting in that PPrune thread. I'm a bit fuzzy on the protocol of posting from another board but I thought this graph about the characteristics of thermal runaway on different Lithium battery chemistries was interesting and pertinent. Post 20 gives a good explanation.
The Lithium cobalt batteries, (similar to the 787 batteries), create the most heat and Lithium Iron Phosphate batteries, (of the type I believe Cessna has switched to), gives off the least.
Caryjack From United States of America, joined May 2007, 265 posts, RR: 0 Reply 111, posted (4 months 2 weeks 6 days 18 hours ago) and read 15562 times:
I would be surprised if designers were still using SCRs in these types of switching power supplies when IGBTs have doing the job for at least 20 years. Commuting circuits and heat sinks (slow speed) work against SCRs.
Quoting okie (Reply 104): gate signal firing angle is calculated off the end of the previous sine wave.
Not sure what you mean here. The gate signal is a DC pulse followed by the much larger DC current flow through the SCR (until the SCR is turned off). Any sine wave would be produced by reactive circuits down stream, the frequency varies with the gate frequency and the energy varies with SCR on time.
Quoting okie (Reply 104): The BMS is not a recording oscilloscope, it would never see such a short event.
Off hand I can't think of a slower electronic switch than an SCR. The BMS could "see" it, it just depends on how much data you want to store.
Quoting JHwk (Reply 105): The development timeline would suggest SCR is possible
SCRs have been around for 40 years or more, IGBTs for 20 or so.
Quoting JHwk (Reply 105): IGBT would be a much more "clean" system.
If you mean fewer, smaller components with much higher efficiency, sure. The down side is the "infectious" harmonic noise caused by the much higher switching frequencies. It just gets into everything.
Quoting JHwk (Reply 105): I assume the battery charger is filtering out the charge current
Battery chargers have filters but by far, the largest filter in that circuit is the battery itself.
Quoting tdscanuck (Reply 106): The battery chargers run off the 28VDC buses...I'm not an electrical guy but I can't see any reason the chargers would have SCRs. If the chargers are getting bad power it's got to be coming down the pipe from the transformer/rectifiers that feed the 28VDC buses.
No switchers required here, SCR, IGBT or otherwise. Current limit and series voltage regulators for sure.
Quoting tdscanuck (Reply 106): Generators produce 230V wild frequency AC
Wild frequency? So it varies with load?
Quoting tdscanuck (Reply 106): Transformer/rectifiers change this to 28VDC to power the DC loads, including the battery chargers
I'd be curious to know how this supply is conditioned. It may include series regulators and current limiters but not switchers to get to the 28 VDC. It just depends on the load sensitivity.
Quoting tdscanuck (Reply 106): Transformers change this to 115VAC (still wild frequency) to power the medium size AC loads Simple enough.
-Transform/rectifiers change this to +-270VDC to power the large motor controllers
These controllers chop and send very narrow pulses of 270 VDC directly to the motors where the motors inductance smooths them to the equivalent DC voltage. As more effort is requested, the controller increases the pulse frequency until the maximum frequency is reached. After that, the pulse width is increased until the full 270 VDC is applied the the load.
Quoting tdscanuck (Reply 106): Quoting JHwk (Reply 105):
Been reading up and finally broke down and joined to post a question/comment.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 112, posted (4 months 2 weeks 6 days 15 hours ago) and read 15478 times:
Quoting JoeCanuck (Reply 108): Would greater containment ever be enough to get these batteries re-certified, if no initiating cause was ever discovered?
My guess is yes, with the FAA agreeing that the risk of a high level event (loss of aircraft) is reduced to an acceptable risk while the NTSB screams in the background that it's unacceptable regardless of containment.
Quoting AirlineCritic (Reply 109): Given that they now are saying multiple batteries were being replaced in Japan in a small fleet of aircraft
This is a hot topic on the CivAv threads...the short version is that, according to the news articles anyway, most of those batteries were replaced for a totally different reason (and one that was completely normal given how the batteries were operated).
It was multiple different (and, so far, unrelated) problems. The fires were freak occurrences...there's no way that every single battery fire that ever occured through the history of the test/certification/service program wouldn't have been reported to the regulators.
Quoting Caryjack (Reply 111): Quoting tdscanuck (Reply 106):
Generators produce 230V wild frequency AC
Wild frequency? So it varies with load?
No, it varies with engine speed. The "D" part of IDGs was always a huge mechanical pain-in-the-rear...the 787 (and A380) did away with that and just direct drive the generator from the engine gearbox, so the frequency moves around with engine speed.
Quoting Caryjack (Reply 111): Quoting tdscanuck (Reply 106):
Transformer/rectifiers change this to 28VDC to power the DC loads, including the battery chargers
I'd be curious to know how this supply is conditioned. It may include series regulators and current limiters but not switchers to get to the 28 VDC. It just depends on the load sensitivity.
Unfortunately, I have no idea how it's done. However, many of the downstream customers of the 28VDC bus are relatively sensitive computers so I'd hope it's pretty good quality power.
Litz From United States of America, joined Dec 2003, 1745 posts, RR: 0 Reply 113, posted (4 months 2 weeks 6 days 10 hours ago) and read 15219 times:
Quoting Seat55A (Reply 101): Thinking about dirty power as a source of problems, do we know if the ground power sources and procedures have been checked out? One of the incidents was on the ground, and the other manifested quite shortly after takeoff and could have been triggered on the ground.
The Boston plane never got hooked up to ground power, and the other incident was airborne....
PITingres From United States of America, joined Dec 2007, 966 posts, RR: 12 Reply 114, posted (4 months 2 weeks 6 days 10 hours ago) and read 15193 times:
I think Seat55A's suggestion was that something on the ground set the stage somehow for the ANA battery failure, but it took long enough to actually fail that the failure manifested in the air.
That feels unlikely to me but I've no facts to back it up with one way or the other -- I think I'm assuming that the event proceeds fairly quickly and I certainly could be wrong about that. I've seen no published data one way or the other.
dalmd88 From United States of America, joined Jul 2000, 2370 posts, RR: 15 Reply 115, posted (4 months 2 weeks 6 days 9 hours ago) and read 15160 times:
Quoting tdscanuck (Reply 112): No, it varies with engine speed. The "D" part of IDGs was always a huge mechanical pain-in-the-rear...the 787 (and A380) did away with that and just direct drive the generator from the engine gearbox, so the frequency moves around with engine speed.
The MD90 also has a wild freq system. I think it was the first one in a commercial jet. There were a ton of teething problems when it first came out, but now I rarely hear a difficulty event for the system.
JoeCanuck From Canada, joined Dec 2005, 5135 posts, RR: 29 Reply 116, posted (4 months 2 weeks 6 days 9 hours ago) and read 15149 times:
Logically, I find it heartening that the investigators are not jumping the gun and speculating about causes and effects, but emotionally, it sucks waiting on details regarding this obviously fascinating subject.
One of the options going forward is undoubtedly going to an entirely new battery chemistry...at least in the long run.
I've lost the post/thread where they give the dimensions and specs of the 787 batteries. I use 36v, 10 cell, 10 amp/hr Lithium Iron Phosphate batteries in my bikes. I'm going to confirm the measurements of my batteries and I'd like to compare the dimensions and what it would take to make a LiFePo4 battery pack with the specs of the 787 pack.
Without a doubt, this chemistry is safer and more stable than the Li-Co's and barring any other constraints, (like certification, etc), I'd like to do a real world comparison to see if a pack can be made that would fit in the current slot, and still provide the required power.
Some more info I copied from PPrune. This is a link to a battery geek's paradise;
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 117, posted (4 months 2 weeks 6 days 8 hours ago) and read 15114 times:
Quoting JoeCanuck (Reply 116): Without a doubt, this chemistry is safer and more stable than the Li-Co's and barring any other constraints, (like certification, etc), I'd like to do a real world comparison to see if a pack can be made that would fit in the current slot, and still provide the required power.
Gotta say I've come to agree with Elon's philosophy over the years.
"Both Boeing and Tesla use batteries fueled by lithium cobalt oxide, which is among the most energy-dense and flammable chemistries of lithium-ion batteries on the market. While Boeing elected to use a battery with a grouping of eight large cells, Tesla's batteries contain thousands of smaller cells that are independently separated to prevent fire in a single cell from harming the surrounding ones.
"Moreover, when thermal runaway occurs with a big cell, a proportionately larger amount of energy is released and it is very difficult to prevent that energy from then heating up the neighboring cells and causing a domino effect that results in the entire pack catching fire," says Musk."
The Tesla pack puts out around 100kw even though they use tiny cells and it fits in a car, so it can't be that big. I use to think using thousands of small cells was inefficient, but there's obviously a good case for it.
Many small cells would be less efficient space and weight wise, but not that bad. Plus, if you have to cut out a string for a bad cell, the battery is still at 98% capacity.
rcair1 From United States of America, joined Oct 2009, 950 posts, RR: 25 Reply 118, posted (4 months 2 weeks 6 days 8 hours ago) and read 15086 times:
AIRLINERS.NET CREW CUSTOMER SERVICE & SUPPORT
Quoting PITingres (Reply 46): I'll also repost my wild-eyed notion of using an aerogel
I don't think it is so wild-eyed. Better individual isolation may be a useful idea. It would require a lot of certification testing tho.
Quoting KELPkid (Reply 57): Would not short circuiting fall under the category of "manufacturing defect?"
Depends upon what caused the short circuit.
Quoting tdscanuck (Reply 112): My guess is yes, with the FAA agreeing that the risk of a high level event (loss of aircraft) is reduced to an acceptable risk while the NTSB screams in the background that it's unacceptable regardless of containment.
Aggreed. If you don't beleive it - go look at the number of cases where FAA says - we're done - and the NTSB says "response unacceptable"
Quoting JoeCanuck (Reply 116): I've lost the post/thread where they give the dimensions and specs of the 787 batteries. I use 36v, 10 cell, 10 amp/hr Lithium Iron Phosphate batteries in my bikes. I'm going to confirm the measurements of my batteries and I'd like to compare the dimensions and what it would take to make a LiFePo4 battery pack with the specs of the 787 pack.
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 119, posted (4 months 2 weeks 6 days 7 hours ago) and read 15069 times:
Quoting rcair1 (Reply 118): Quoting KELPkid (Reply 57):
Would not short circuiting fall under the category of "manufacturing defect?"
Depends upon what caused the short circuit.
Irregardless, the laptop solution is that there is a fuse in every battery cell, and if a short happens, the fuse blows. The battery is useless at that point, but it sure beats a thermal runaway in your lap
The scandal with Dell and Apple laptops (around 2006 or so?), IIRC, involved shoddily-made LiIon cells in their battery packs which were made by Chinese knock-off manufacturers, who didn't get the fuse piece quite right...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
Very true...I'm just going by what I have some experience with...and with what Cessna seems to have chosen for their CJ-4. Boeing, the manufacturers of components, the investigators, regulators and airlines all know way better than I ever could what are the best options. I'm just curious about the size that a LiFePo4 pack would be which could match the 787's power requirements.
I happen to have some packs so I can make some physical measurements for comparison. It's really just a thought exercise to satisfy my curiosity.
Quoting nomadd22 (Reply 117): The Tesla pack puts out around 100kw even though they use tiny cells and it fits in a car, so it can't be that big. I use to think using thousands of small cells was inefficient, but there's obviously a good case for it.
We used hundreds of AA alkalines to power some tools used to test oil wells. Nothing wrong with small cells...you can series/parallel them in myriad ways to get almost any power or size configuration you want. The flip side is the more cells, the greater the chance of failure so you have to safeguard against not only a failure damaging adjacent cells, but also rendering the entire pack useless. If done right, you end up with a very safe and reliable system where, as you mention, one cell failure merely results in a relatively small loss of capacity.
Instead of one big battery, there's something to be said for individually removable and replaceable cells/packs so one bag egg can be replaces without having to get a whole new pack. Each removable pack would also act as its own containment.
That being said, LiFePo4's just don't react as dramatically to abuse as Li-Co. I've had one cell of one pack fail and all it did was reduce capacity...no harm to other cells and no drama...with less isolation than the 787 packs. I've had the packs frozen down to -40c without any degradation in performance...though I don't have nearly the cojones to actually charge or use the packs until they are warmed to room temperature.
With all the drama surrounding the grounding, it's easy to forget that the 787 batteries have accumulated over a million hours of testing, including over 100,000 flight hours. They were abused in probably every way imaginable and they, and the containment, passed. Some very smart cookies worked on these things and more are working on discovering what happened and how to fix it.
I think they'll have the cause(s) in short order and are probably already testing solutions and alternatives now. Whatever they choose is irrelevant as long as it is safe and it works.
Starlionblue From Hong Kong, joined Feb 2004, 15904 posts, RR: 66 Reply 121, posted (4 months 2 weeks 6 days 6 hours ago) and read 15044 times:
Quoting nomadd22 (Reply 117): The Tesla pack puts out around 100kw even though they use tiny cells and it fits in a car, so it can't be that big.
It is quite large; much bigger than the 787 battery. Here's a pic of the 53kWh Tesla Roadster battery. The model S battery is up to 85kWh and even larger, though a very different shape as it makes up the "floor" of the car.
Compare to the relatively small 787 one.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
mham001 From United States of America, joined Feb 2005, 3017 posts, RR: 2 Reply 122, posted (4 months 2 weeks 6 days 6 hours ago) and read 15033 times:
Quoting JoeCanuck (Reply 120): I happen to have some packs so I can make some physical measurements for comparison. It's really just a thought exercise to satisfy my curiosity.
I happen to have in my garage a pack of 8 LiFePo4's for 24v (25.6 nominal), 180Ah for an off-grid home. Dimension of the Huggy box they fit in so nicely is 11" high, 14" wide and 15" long. Here are all the specs for a 60Ah version of the same battery....
Capacity: 60Ah nominal
Voltage: 3.2
Charge Voltage: 3.6v - use 3.5v for series strings.
Discharge Cutoff: 2.50v
Standard Charge/Discharge: 0.3 C ( 18 amps).
Max Charge: 3C (180 amps)
Max Continuous Discharge: 3C -180 amps.
30 second Discharge: 10C - 600 amps.
Height: 9.75 inch/248mm
Width 4.53 inch/115 mm
Thickness: 1.61 inch/41 mm
Weight: 4.45 lbs/2.0 kg
You can figure the dimensions of the Boeing box by the picture above. it is ~1 cu. ft. There could also be some issues with voltages as the lithium potassiums have a slightly lower voltage (you would need 9 for 28v nominal) but in my world, dc voltage just needs to be close,
Fantastic, thanks. My batteries have somewhat different properties. Mine actually have a higher rated voltage as well as nominal voltage, though the charge - cutoff range is similar 12volts v. 11volts.
I'm a bit confused about what numbers are used to specify the rated voltage of the 787 battery...I assume since they use 8 cells for 32v, they're using what I assume is the charge voltage of 4.0v/cell. If that's how they are rating these batteries, it would take 8 of my cells, (I use 'my' for convenience's sake...I'm not taking credit for the cells themselves), in series to give 33.6v. 6 of these 8 cell sets, (in parallel), would make a 60 A/hr battery pack...7 sets would make a 70 A/hr pack, effectively straddling the current 787 pack...(from what I assume...).
The setup I have is very conservative. I charge at 0.2c (2 Amps) and have a maximum continuous discharge of 1.5c (15 Amps). The motor, controllers and chargers I use are safe for other li-ion types so vaIues are set at a safe level for the least robust battery chemistries. I assume the maximum charge/discharge rates are similar to yours.
So a configuration of 6 packs of 8 cells each, (without any containment), would be, (in one configuration);
H - 11.1" (284mm)
w - 5.9" (152mm)
L - 4.8" (123mm)
Seven cell sets would be larger but probably still fit into a 1 cubic foot box.
The weight of a 60 A/hr pack would be 24kg...a 70kg pack would be 28kg. These are just cell weights; containment not included. 8 x lvp65 cells weigh 22kg.
The LVP65 data is from the link rcair1 provided. There is a very good chance some of my figures are off or just wrong. Feel free, (if one feels so inclined), to double check. I'd rather know the facts than pretend to be right. I have fat fingers and am easily distracted by shiny things.
Hopefully this is somewhat interesting, (it was to me). All are invited to edit to their heart's content.
JoeCanuck's LiFePo4's
Dimensions inches(mm)
Measured
Case size - 18.5(470) x 3.0(76) x 3.25(82.5)
Battery pack length (inside case) - 14.0(356)
Cell size - 2.8(71) x 1.5(38) x 1.6(41)
Cell weight - 0.5kg
Cell voltage - 3.6 (4.2-3.0)
Charge voltage - 42 @ 2amps.
Discharge cutoff - 3.0v
Cell capacity (Ah)- 10
Calculated
Specific energy wh/kg - 72
Energy density wh/l - 324
LVP65
Voltage 3.7 (assumed range, 4.0 charge voltage - 3.4v drain cutoff)
Capacity rated 65 Amp/hr
nominal 75 Amp/hr
width 132
thickness 50
height 178
weight 2.75 kg
specific energy wh/kg 2.75
energy density wh/l 232
Max charge rate (ca) 1.0
max discharge rate (ca) 5.0
ferpe From France, joined Nov 2010, 1944 posts, RR: 56 Reply 124, posted (4 months 2 weeks 6 days ago) and read 14845 times:
It seems that B is having at least one path that may work and not require the long lead times of a new battery and changes to the electronics, also the way Cessna and Airbus seems to have taken:
"Sources say that Boeing is seriously considering a better containment system that solves both the collateral damage to other sensitive equipment and deals with the smoke better. The plan is to build a stronger and larger containment box or dome around the battery, and vent smoke and potential debris overboard through a hose or other channel. "
Aviaponcho From France, joined Aug 2011, 276 posts, RR: 4 Reply 125, posted (4 months 2 weeks 5 days 21 hours ago) and read 14763 times:
Hello
Thank you all, JoeCanuck, mham001
Cessna had a 18 months homework for its not new (same technology) reinforced battery. In these 18 months, how much can be induced by the fact that is was novelty for FAA ? How long will it take today for the same task ? It might be quicker.
The new containment will be larger. Where will boieng put it ? Is there any pictures of the forward Avionic bay ?
Changing venting routing, separating air flow from batteries from the avionic air flow suppose an new outlet I think? And suppose to reconfigure the air flow management system.
Nothing trivial in fact.
By the way LiPo seems to be a good compromise and a cheap one (price vs Li-ion technology is lower I think) but that's another subject.
In the end, Boeing's statement on the 2012 earning conference seems to have been written before the grounding...
dynamicsguy From Australia, joined Jul 2008, 778 posts, RR: 8 Reply 126, posted (4 months 2 weeks 5 days 19 hours ago) and read 14720 times:
Regarding the choice of Tesla to use thousands of smaller cells: quite some time ago I went to a talk hosted by a guy from Tesla for a group of mostly solar car nerds. Since we use various forms of Li-ion cells in our packs this topic was of interest and the question of why so many small cells was raised. The answer was that it was an economic decision since smaller cells were mass produced already for a large number of devices so it was a far cheaper way of building such a high capacity battery.
The ability to separate cells may have been a secondary factor, but it also brings with it many more opportunities for failure and that many more cells for the BMS to look after.
Pihero From France, joined Jan 2005, 3598 posts, RR: 72 Reply 127, posted (4 months 2 weeks 5 days 19 hours ago) and read 14856 times:
Quoting ferpe (Reply 124): It seems that B is having at least one path that may work and not require the long lead times of a new battery and changes to the electronics,
Same article I just discovered on Leehamnet.
The interesting excerpt : " Boeing CEO Jim McNerney did not talk about solutions, but said the company planned to stick with the controversial lithium ion batteries as the best option for the plane."
Doesn' t that mean that in fact, "they" think the incidents were due to manuifacturing defects / quality control and that doesn't change the validity of the Lion technology ?
Thank you all for all the infos you give to this thread : I'm learning a lot, and it's humbling as I thought I was on top of aircraft technology. Now I really understand that there was a lot more to the 787 than the over-hyped CRFP construction.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 128, posted (4 months 2 weeks 5 days 14 hours ago) and read 14710 times:
Quoting Aviaponcho (Reply 125): The new containment will be larger. Where will boieng put it ? Is there any pictures of the forward Avionic bay?
Changing venting routing, separating air flow from batteries from the avionic air flow suppose an new outlet I think? And suppose to reconfigure the air flow management system.
Nothing trivial in fact.
As I understand it, the containment vessels for the four Li-Ion batteries on the A350XWB are directly vented to the outside so leaking electrolyte and smoke/fumes do not escape into the EE bay (at least in any serious amount).
Such a system would mean Boeing would not need to significantly enlarge the containment vessel of the 787 batteries because they would no longer need to hold the material - it would be vented to the outside.
And I don't see how it would materially impact airflow in the EE bay. During normal operation the internal venting would be closed (so it would operate like the current system does) and when it does open, it's not going to be some giant vacuum pump.
okie From United States of America, joined Jul 2003, 2410 posts, RR: 3 Reply 129, posted (4 months 2 weeks 5 days 14 hours ago) and read 14683 times:
Quoting Stitch (Reply 128): And I don't see how it would materially impact airflow in the EE bay. During normal operation the internal venting would be closed (so it would operate like the current system does) and when it does open, it's not going to be some giant vacuum pump.
Ok, but I am just not sure you can just bore a couple holes for the two battery vents in CRFP.
Quoting tdscanuck (Reply 106): -Transformer/rectifiers change this to 28VDC to power the DC loads, including the battery chargers
Doable but would seem unusual to charge a battery needing a charge voltage of 32vdc off a 28vdc buss. Just do not know the architecture.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 130, posted (4 months 2 weeks 5 days 13 hours ago) and read 14630 times:
Quoting okie (Reply 129): Ok, but I am just not sure you can just bore a couple holes for the two battery vents in CRFP.
Sure you can. The plane has plenty of holes drilled into it for other things (potable water, fuel, sewage, air flow, etc.).
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 131, posted (4 months 2 weeks 5 days 12 hours ago) and read 14602 times:
Quoting Stitch (Reply 130): Quoting okie (Reply 129):
Ok, but I am just not sure you can just bore a couple holes for the two battery vents in CRFP.
Sure you can. The plane has plenty of holes drilled into it for other things (potable water, fuel, sewage, air flow, etc.).
I'd think the most you would need is a thick spot where you made the vent. Maybe nothing but the fitting if it's a low load spot. We use liquid acid batteries on our ships that have a very simple vent to keep air constantly flowing around and out.
Thanks for the photo Stationblue. But, isn't the 787 battery only about 2 kwh? My comparison was poorly worded. I should have said a Tesla type battery of 787 battery capacity. The numbers I see around the internet come in at Tesla batteries being about 50% heavier than 787 batteries per kwh.
Aviaponcho From France, joined Aug 2011, 276 posts, RR: 4 Reply 132, posted (4 months 2 weeks 5 days 9 hours ago) and read 14435 times:
Quoting Stitch (Reply 128): And I don't see how it would materially impact airflow in the EE bay. During normal operation the internal venting would be closed (so it would operate like the current system does) and when it does open, it's not going to be some giant vacuum pump.
Hello Stitch
The piping work will certainly be easy.
But you must be sure that you won't vent smoke from the forward Avionic bay in air conditioning air-scoop, or other air-scoop
You must be sure that you're not venting electrolyte in the same airscoop
You must monitor this system, and make sure you won't go at FL35 with the vent open ?
You must set up maintenance guidance
And so on
Isnt'it ?
A simple and robust solution for sure, but not so trivial I think if not build in
strfyr51 From United States of America, joined Apr 2012, 488 posts, RR: 0 Reply 133, posted (4 months 2 weeks 5 days 8 hours ago) and read 14426 times:
Boeing seems to be standing by the Lithium Ion battery for now but I think it's a lost cause. that battery is not ready for Commercial Airline use and unless they come with a miracle for Boeing and the airlines are in a position to Lose ETOPS authority completely! Then the 787 will be nothing more than a carbon Fiber 757. They can come up with a retrofit to install 2 Nicad's fwd and 2 nicads aft. The weight penalty is negligible. They KNOW what they can do, What they want and what they Will do is the Story.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 134, posted (4 months 2 weeks 5 days 8 hours ago) and read 14421 times:
Quoting Aviaponcho (Reply 132): A simple and robust solution for sure, but not so trivial I think if not build in.
The front EE bay already has an outflow vent for smoke and a drain plug for electrolyte and other liquids and they don't put material into the Pack Scoop, so I would just route the plumbing to vent right next to them and problem solved.
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 135, posted (4 months 2 weeks 5 days 8 hours ago) and read 14396 times:
If they can mess with the container without screwing up certification, I wonder if they might be able to make it a few inches bigger in order to put barriers between cells and prevent fratricide.
Humanitarian From United States of America, joined Jan 2012, 83 posts, RR: 0 Reply 136, posted (4 months 2 weeks 5 days 5 hours ago) and read 14290 times:
Quoting Stitch (Reply 134): The front EE bay already has an outflow vent for smoke and a drain plug for electrolyte and other liquids and they don't put material into the Pack Scoop, so I would just route the plumbing to vent right next to them and problem solved.
Agreed, and I think they just file an for an expedited STC or being the OEM, do they need to file an STC or just amend the type certificate?
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 137, posted (4 months 2 weeks 5 days 2 hours ago) and read 14274 times:
Quoting okie (Reply 129): Ok, but I am just not sure you can just bore a couple holes for the two battery vents in CRFP.
You can. And the lord said...let there be titanium doubler plates...
Quoting strfyr51 (Reply 133): that battery is not ready for Commercial Airline use
If you mean *that* battery, the evidence seems to point that way. The evidence for lithium-ion, in general, for commercial airplane use is well established though, so it's not the technology that's particularly the problem.
Quoting strfyr51 (Reply 133): and unless they come with a miracle for Boeing and the airlines are in a position to Lose ETOPS authority completely!
I don't think ETOPS is really an issue...nothing about the battery is particularly tied in to ETOPS (the battery can't power the airplane for ETOPS durations). The plane will either not fly at all, or it will fly as designed. There's no reason to end up in the middle.
Quoting Humanitarian (Reply 136): Agreed, and I think they just file an for an expedited STC or being the OEM, do they need to file an STC or just amend the type certificate?
It can be either, but normally it's an amended TC.
okie From United States of America, joined Jul 2003, 2410 posts, RR: 3 Reply 138, posted (4 months 2 weeks 5 days 2 hours ago) and read 14229 times:
Quoting tdscanuck (Reply 137): If you mean *that* battery, the evidence seems to point that way. The evidence for lithium-ion, in general, for commercial airplane use is well established though, so it's not the technology that's particularly the problem.
The crumbs seem to be leading a trail back to the cell manufacturer from what I can see with the public information available.
Whether it is a QC issue with materials or manufacturing process issue I would not know.
The question I would have if Thales went to another cell manufacturer what would be the time frame of the approval process.
or
Could Boeing use another supplier other than Thales with another cell manufacturer and get approval quickly.
Would FAA just consider a Li-ion battery is the same regardless of manufacturer?
You are correct about the Lithium-ion technology, it is here to stay.
kanban From United States of America, joined Jan 2008, 2500 posts, RR: 21 Reply 139, posted (4 months 2 weeks 4 days 21 hours ago) and read 14126 times:
probably another unanswerable question, however the other 48 planes out there, have the batteries been removed, are they being monitored.?.. will some cleaning person leave a lavatory light on and drain them ?
zeke From Hong Kong, joined Dec 2006, 7770 posts, RR: 73 Reply 141, posted (4 months 2 weeks 4 days 20 hours ago) and read 14149 times:
Quoting okie (Reply 138): The crumbs seem to be leading a trail back to the cell manufacturer from what I can see with the public information available.
Whether it is a QC issue with materials or manufacturing process issue I would not know.
The cell inside a battery itself is a relatively simple chemical process, however it is integrated into a part that probably includes a housing, and some electronics. A perfect cell will misbehave if it is put outside of its design tolerances, this include voltages, currents, and temperatures. Monitoring temperature in a Li-ion cell is critical, and may require physical barrier between cells within the battery assembly to prevent and absorb excessive heat.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
strfyr51 From United States of America, joined Apr 2012, 488 posts, RR: 0 Reply 142, posted (4 months 2 weeks 4 days 12 hours ago) and read 13945 times:
Thales didn't build or design that particular Lithium Ion Battery, the Company is GS Yuasa out of Japan. They designed it for light weight and ease of Maintenance (they Claim) I believe Boeing should have second sourced the Lithium Ion Battery or resort to 4 Ni-Cads and go beyond the 32VDC as an Overkill until a new Battery can be found that Doesn't seem to lose it's cool, 4 v.DC from a cell is a pretty tall order Most Ni-Cad Batteries carry 1.4v.DC reliably so 2 ea. 18v.DC with
36-40 Amp Hrs in the fwd and aft compartments should do nicely.
rwessel From United States of America, joined Jan 2007, 2005 posts, RR: 2 Reply 143, posted (4 months 2 weeks 4 days 12 hours ago) and read 13917 times:
Quoting strfyr51 (Reply 142): 4 v.DC from a cell is a pretty tall order Most Ni-Cad Batteries carry 1.4v.DC reliably
The voltage per-cell is a function of chemistry. Something near 3.7V is normal for most of the Lithium Ion variations, just like 1.2V is normal for a NiCd cell. You design your battery with the right combination of cell sizes and array layout (number of parallel and series lines) to meet your desired output voltage, output current and capacity, and those tradeoffs are different for different chemistries.
So if the battery were redesigned with half-sized cells, for example, you'd end up with 16 cells arranged in a two-parallel/eight-in-series array, with each cell still putting out ~3.7V, but only half the current.
bradmovie From United States of America, joined Jan 2013, 16 posts, RR: 0 Reply 144, posted (4 months 2 weeks 4 days 10 hours ago) and read 13805 times:
I'm wondering about using the APU battery for ground power and whether anything is different about battery monitoring and lockouts/shutdowns/safety procedures than it is in the air. I don't believe anyone has addressed this in either thread, though it's a lot of posts!
Does using the APU battery for ground power activate any of the aircraft's safety systems for the battery? Do any computer functions power up besides monitoring refueling/fuel door or activating position lights that have relevance to battery safety? Does the aircraft monitor voltage and imbalances and shut the battery down automatically if it has a risk of runaway or other problem? What would happen if it did -- any risk of spilled fuel or damage?
If so I don't understand how one can use the APU battery on the ground for "too long". Isn't there a battery shutoff if the charge becomes too depleted? How could simply using the battery for what it was designed cause multiple battery failures, and lead people to think that misuse of the APU battery on the ground may be implicated in battery problems? Again, I'm not involved in aircraft certification at all, just a private pilot, but I can't imagine Boeing would simply say to its customers "don't use this battery for more than x minutes at a time or it will cost you $16,000".
I'm no expert, and I'm not trained in using fault trees, just trying to use some logic here. Thanks.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 145, posted (4 months 2 weeks 4 days 8 hours ago) and read 13757 times:
Quoting bradmovie (Reply 144): I'm wondering about using the APU battery for ground power and whether anything is different about battery monitoring and lockouts/shutdowns/safety procedures than it is in the air. I don't believe anyone has addressed this in either thread, though it's a lot of posts!
I don't believe the APU battery is used to power anything other than the APU start.
The Ship's Battery (the main battery under the flight deck) is the one that can provide ground power to some systems if no other ground power source is available.
dalmd88 From United States of America, joined Jul 2000, 2370 posts, RR: 15 Reply 146, posted (4 months 2 weeks 4 days 4 hours ago) and read 13611 times:
Quoting Stitch (Reply 145): I don't believe the APU battery is used to power anything other than the APU start.
The Ship's Battery (the main battery under the flight deck) is the one that can provide ground power to some systems if no other ground power source is available.
I also think this is true. Every other Boeing works this way. It is a redundancy factor. If you kill the ship battery you can still attempt to start the APU and get it's generator running. Starting the APU really cycles the APU battery. I don't know how many start attempts you get just of the battery without recharge, but I would bet three maybe four.
Not every!
The B737-200 and 300 have a single battery that does both functions.
The B737-400 had the option of a second battery. This was usually dedicated to APU start, but was located in the fwd EE bay. But in the emergency case where the battery was supplying standby power, both batteries were paralleled together. The APU battery is not on the MEL, both must be serviceable for dispatch.
Seemed strange to me. The second battery was an option, not fitted to all B734, but was not on MEL.
gigneil From United States of America, joined Nov 2002, 16215 posts, RR: 88 Reply 148, posted (4 months 2 weeks 3 days 12 hours ago) and read 13273 times:
Quoting strfyr51 (Reply 133): Boeing seems to be standing by the Lithium Ion battery for now but I think it's a lost cause. that battery is not ready for Commercial Airline use and unless they come with a miracle for Boeing and the airlines are in a position to Lose ETOPS authority completely! Then the 787 will be nothing more than a carbon Fiber 757. They can come up with a retrofit to install 2 Nicad's fwd and 2 nicads aft. The weight penalty is negligible. They KNOW what they can do, What they want and what they Will do is the Story.
Cessna and Airbus are going to keep the Li batteries as well... its going to be fine.
Quoting tdscanuck (Reply 137): I don't think ETOPS is really an issue...nothing about the battery is particularly tied in to ETOPS (the battery can't power the airplane for ETOPS durations). The plane will either not fly at all, or it will fly as designed. There's no reason to end up in the middle.
Its the fire and containment issue that's going to cause the ETOPS issue - if one runs away while over the South Pacific between AKL and SCL, the only way to make it stop right now is to land in the ocean.
I think its solveable, but there has been definite rumbling of ETOPS issues.
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 150, posted (4 months 2 weeks 3 days 4 hours ago) and read 13001 times:
Apparently, according to the Civ/Av discussion, the NTSB is now interested in the "Battery Contactors" and has focused the investigation in that direction. Anyone know what Battery Contactors are?
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
Caryjack From United States of America, joined May 2007, 265 posts, RR: 0 Reply 151, posted (4 months 2 weeks 2 days 23 hours ago) and read 12902 times:
Quoting gigneil (Reply 148): if one runs away while over the South Pacific between AKL and SCL, the only way to make it stop right now is to land in the ocean.
This is stupid. From all accounts the fuel supplying the fire would be contained and consumed before the airliner reached the water. Even if I'm wrong, the ocean couldn't stop it.
Quoting KELPkid (Reply 150): Anyone know what Battery Contactors are?
Contactors provide the contact points in electrical relays whose function is to switch high power to the load. Contactors are used in all types of high power mechanical switching circuits including traction motors and converters. In a chin of events, they are the final and largest electronic device (inductors) activated which turn on the load. Some are are open to inspection, field serviceable (adjust, clean, replace parts), and contain auxiliary contacts to indicate state. They can be removable modules of 40 lbs and pulled for service.
Thanks,
Cary
Deltal1011man From United States of America, joined Sep 2005, 8628 posts, RR: 8 Reply 152, posted (4 months 2 weeks 2 days 19 hours ago) and read 13035 times:
Quoting gigneil (Reply 148): Cessna and Airbus are going to keep the Li batteries as well... its going to be fine.
Like it or not this is the future. Boeing will get it worked out. (Only way i see the NiCad talk is if we start looking at years when talking about the grounding vs months)
"Oh look at the sUGAr falling out of the sky! Look at the sUGAr falling out of the sky!" LM 1922-2011 Go Dawgs! G.A.T.A.
Tristarsteve From Sweden, joined Nov 2005, 3713 posts, RR: 34 Reply 153, posted (4 months 2 weeks 2 days 19 hours ago) and read 13045 times:
Quoting Caryjack (Reply 151): Some are are open to inspection, field serviceable (adjust, clean, replace parts), and contain auxiliary contacts to indicate state. They can be removable modules of 40 lbs and pulled for service.
Bit big for an aircraft!
Biggest ones are about the size of your fist and weigh a kilogram. They are changed as an LRU and not opened up.
Seat55A From New Zealand, joined Jan 2013, 31 posts, RR: 0 Reply 154, posted (4 months 2 weeks 2 days 16 hours ago) and read 12948 times:
Wonder if the interest in the Contactors is just the next thing, or if it is specifically related to findings?
I am having a hard time believing that the unexpected high number of battery replacements is totallly unrelated to the more serious failures. I can see maintenance draining them to the lockout point by mistake once or twice, but after that surely an internal communication happens, "hey, these batteries drain quickly, watch out." Strange if these professionals are still making the same expensive and embarassing mistake after a whole year of operations.
If a Contactor has some kind of fault that could explain the excess drain.
JoeCanuck From Canada, joined Dec 2005, 5135 posts, RR: 29 Reply 155, posted (4 months 2 weeks 2 days 9 hours ago) and read 12779 times:
Quoting gigneil (Reply 148): Cessna and Airbus are going to keep the Li batteries as well... its going to be fine.
After doing some googling, I've discovered that Cessna is using Lithium Iron Phosphate batteries, not Lithium Cobalt, and it was using LiFePo4 batteries when the CJ-4 caught fire. I can't seem to find very many details on the fire other than it was started after a ground power unit was plugged in but details about what actually caught fire and the exact causes are scarce.
So as much as I'm a fan of LiFePo4 batteries, they, (any battery, actually), can be a fire hazard under certain circumstances.
There never will be a 100% fireproof battery of any chemistry so whatever is decided, containment will be a key component.
strfyr51 From United States of America, joined Apr 2012, 488 posts, RR: 0 Reply 156, posted (4 months 2 weeks 2 days 4 hours ago) and read 12609 times:
Nothing more than large Relays, used to power the airplane from the batteries and facilitate charging TO the batteries
from whatever charging source is available. Boeing uses battery chargers, Airbus uses Aircraft power via Battery charge limiters different name virtually the same in operation.
Caryjack From United States of America, joined May 2007, 265 posts, RR: 0 Reply 157, posted (4 months 2 weeks 1 day 21 hours ago) and read 12448 times:
Quoting tdscanuck (Reply 112): I'd be curious to know how this supply is conditioned. It may include series regulators and current limiters but not switchers to get to the 28 VDC. It just depends on the load sensitivity.
Unfortunately, I have no idea how it's done. However, many of the downstream customers of the 28VDC bus are relatively sensitive computers so I'd hope it's pretty good quality power.
I was looking for something like "29.8 Vdc nominal with 125 mV full load ripple". I'm sure it's from 3 phase alternators so it's going to be fairly stiff with low ripple under full load. OEMs would have had access from Boeing to the 28 Vdc bus specs so those loads are well isolated and protected.
Thanks for the data sheet. Someone up thread has brought charger supply voltage up but I've just now seen the battery data. It looks to me like the ships 28 VDC supply is too low to fully charge the batteries. Is there another bus, say 32 VDC, or is there an inverter (switching PS) integrated into the charger to up the voltage? An inverter would broaden the input voltage operating range, and provide a great deal of isolation but complicate the charger and add noise to the charge current. Packaged switching power supplies are popular but it can be very difficult to get them to play together...I heard the term "bad neighbor" up thread I believe, and it would apply here.
Quoting Tristarsteve (Reply 153): Bit big for an aircraft!
Biggest ones are about the size of your fist and weigh a kilogram. They are changed as an LRU and not opened up.
Looks like my secret's out...I'm not actually in the airline industry. But I did edit my profile.
Quoting Seat55A (Reply 154): If a Contactor has some kind of fault that could explain the excess drain.
A failed converter contactor will not drain the battery.
Contactors switch heavy current loads and over time build up resistance from arcing and pitting. This resistance develops voltage drops which dissipate energy and eventually can cause it to fail, welded shut or brunt open. Other sources of heat are poorly installed cable crimp connectors and faulty or poorly installed fastening hardware. I doubt very much the problem is here.
Auxalliery contacts are another area of interest. These are signal contacts that mechanically or otherwise track the load contactor and indicate state. They also supply a hold-in circuit to limit coil current once the contactor is pulled in. Contactors can have 12 or more sets of Aux contacts. Aux contacts can fail with both over and under current, poor installation and contamination. Of these, contamination by air born particles is easily the most common failure mode.
Lastly, for me anyway, the insulation between the coil circuit and load circuit can break down which removes the designed in isolation between the 2 circuits
.
Thanks,
Cary
Litz From United States of America, joined Dec 2003, 1745 posts, RR: 0 Reply 158, posted (4 months 2 weeks 1 day 9 hours ago) and read 12115 times:
Quoting gigneil (Reply 148): Its the fire and containment issue that's going to cause the ETOPS issue - if one runs away while over the South Pacific between AKL and SCL, the only way to make it stop right now is to land in the ocean.
We used to toss lithium in water in chemistry class... "land in the ocean" now sounds like an even worse idea than before..
On Feb 5th 2013 the JTSB released a second progress report in Japanese reporting that all 8 cells of the damaged battery, nominal voltage 29.6V, 75 Ah capacity at 28.5kg/63 lbs, showed thermal damage before the thermal runaway, particularly cells 3 and 6 are damaged. The positive electrode of cell 3 shows substantial damage and a hole, the internal wiring has melted down.
KC135Hydraulics From United States of America, joined Nov 2012, 165 posts, RR: 0 Reply 162, posted (4 months 2 weeks 2 hours ago) and read 11303 times:
So are we back to saying it might have been a battery manufacturing issue and not a problem specifically with the jet? Or perhaps higher than anticipated discharge/recharge cycles were damaging the batteries slowly over time until they finally had enough. The damage during one cycle might have been undetectable until the sum total of damages reached critical mass and lead to the thermal runaways. Interesting! If that's true, the battery design itself just might not be ready for the application.
Seat55A From New Zealand, joined Jan 2013, 31 posts, RR: 0 Reply 163, posted (4 months 1 week 6 days 18 hours ago) and read 11138 times:
Quoting KC135Hydraulics (Reply 162): So are we back to saying it might have been a battery manufacturing issue and not a problem specifically with the jet?
Boeing' is wanting test flights to get data on vibration and temperature change - possible working hypothesis on root cause is something about condensation in the battery case according to Seattle Times article linked in CivAv previously http://seattletimes.com/html/busines...8074_dreamlinertestflightsxml.html
rcair1 From United States of America, joined Oct 2009, 950 posts, RR: 25 Reply 164, posted (4 months 1 week 6 days 11 hours ago) and read 10867 times:
AIRLINERS.NET CREW CUSTOMER SERVICE & SUPPORT
Quoting okie (Reply 149): I am back to the original question can Thales move to a different cell manufacturer and not have to go back through a major certification process.
Unlikely. Nobody can assure batteries cannot run away. The containment system must contain it. So if the FAA determines the issue is with containment - changing the cell vendor is irrelevant.
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 165, posted (4 months 1 week 6 days 10 hours ago) and read 10821 times:
Quoting rcair1 (Reply 164):
Unlikely. Nobody can assure batteries cannot run away. The containment system must contain it. So if the FAA determines the issue is with containment - changing the cell vendor is irrelevant.
It's not irrelevant when calculating overall odds of an event affecting safety.
kanban From United States of America, joined Jan 2008, 2500 posts, RR: 21 Reply 166, posted (4 months 1 week 6 days 7 hours ago) and read 10743 times:
Quoting nomadd22 (Reply 165): It's not irrelevant when calculating overall odds of an event affecting safety.
Maybe a better way of putting it is: If a new containment system meets the FAA criteria and the planes are flying again, then Thales/Boeing/Yuasa can look at improving the battery or look at other manufacture's products that are more robust without being subjected to the 'got to get the planes flying again pressure'.
There is no way after this the Boeing will go 'Whew, we're done with that issue!'
There are few vendor designed systems that are not improved over time as new technologies or manufacturing processes are incorporated.
HAWK21M From India, joined Jan 2001, 31228 posts, RR: 58 Reply 167, posted (4 months 1 week 6 days ago) and read 10531 times:
Quoting KC135Hydraulics (Reply 162): the battery design itself just might not be ready for the application.
If Boeing plans a replacement Battery type to those used on its previous types,incur a load penalty, get the B787s flying & then work on a mod for the battery subsequently.
in thi statevthe 787's apu battery is used aqs welllas the main ships battery for ground towing operations so getting the airplane to the gate could be a major undrtaking as the brakes and lights
AeroWesty From United States of America, joined Oct 2004, 19266 posts, RR: 63 Reply 170, posted (4 months 1 week 5 days 8 hours ago) and read 10198 times:
Quoting Kaiarahi (Reply 168): NTSB presentation and press release, Feb 7:
The video of the press conference is online now, too. I also posted this link in the CivAv thread, but know some no longer follow that thread. It's 41 minutes long:
Pihero From France, joined Jan 2005, 3598 posts, RR: 72 Reply 171, posted (4 months 1 week 5 days 6 hours ago) and read 10113 times:
Letter from Leeham.net :
FAA Authorizes 787 Test Flights
by leehamnet
Statement from Secretary LaHood and FAA Administrator Huerta:
As part of our ongoing efforts to determine the root cause of recent Boeing 787 lithium-ion battery incidents, the FAA will permit Boeing to conduct test flights of 787 aircraft to gather additional data. The traveling public’s safety is our highest priority. These test flights will be an important part of our efforts to ensure the safety of passengers and return these aircraft to service.
Test flights are commonly used as part of research and development. In this case, the primary purpose of the test flights will be to collect data about the battery and electrical system performance while the aircraft is airborne.
Does that mean that the root cause is identified / being investigated ?
"As with all test flights, these will be subject to a number of restrictions, including extensive pre-flight testing and inspections and in-flight monitoring in order to ensure the highest levels of safety. The flights will be conducted in defined airspace over unpopulated areas.
The test flights will be conducted through a Special Airworthiness Certificate (for the purpose of Research and Development) under the following requirements:
Before flight, the crew must perform a number of inspections to verify that the batteries and cables show no signs of damage.
Pre-flight checklist will include a mandatory check for specific status messages that could indicate possible battery problems.
While airborne, the crew must continuously monitor the flight computer for battery related status messages, and land immediately if one occurs."
The last sentence seems to me a bit harsh... unless the alerting / message / alerting levels and priority system is being looked after. Remember, in the initial press reports, the decision to divert and land in emergency wsqasn't ( professional opinion ) warranted by the merssages displayed... although, with hinsight, the crew was right.
"Before the initial test flight, the crew must inspect the airplane’s smoke barriers and insulation to verify that they meet the approved design."
Are they now hinting at FAL defects and QA ?
"Experimental research and development flights are flown with Boeing aircrews that include only personnel essential to the flight.
In addition to the FAA’s root cause analysis, the FAA is conducting a comprehensive review of the 787’s critical systems, including the aircraft’s design, manufacture and assembly."
kanban From United States of America, joined Jan 2008, 2500 posts, RR: 21 Reply 172, posted (4 months 1 week 5 days 3 hours ago) and read 10012 times:
Quoting Pihero (Reply 171): Are they now hinting at FAL defects and QA ?
I would read that as .. since they are using a test a/p, that they ensure these items have not be rearranged with testing and test equipment.
Quoting Pihero (Reply 171): he FAA is conducting a comprehensive review of the 787’s critical systems, including the aircraft’s design, manufacture and assembly."
I read that as boilerplate added by legal and public relations.. basically the FAA doesn't have the manpower to do more that a comprehensive analysis of just the affected systems.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 173, posted (4 months 1 week 5 days 2 hours ago) and read 9984 times:
Quoting Pihero (Reply 171): Does that mean that the root cause is identified / being investigated?
Boeing evidently has some theories regarding vibration and moisture penetration within the battery enclosure and these items are some of those that will be tested for.
Quoting Pihero (Reply 171): Are they now hinting at FAL defects and QA?
The batteries themselves show internal failures, though whether that is caused by poor QA at Yuasa or external elements has yet to be determined. And UA found incorrect wiring on the loom that feeds the APU battery system on one of their 787s during inspections they voluntarily undertook after the BOS incident.
So I could see the FAA wanting to make sure the assembles were properly put together and then the completed units properly installed and connected in the airframe.
Quoting Pihero (Reply 171): In addition to the FAA’s root cause analysis, the FAA is conducting a comprehensive review of the 787’s critical systems, including the aircraft’s design, manufacture and assembly."
Same question as above...
The FAA had already planned a review of the 787's electrical system in the wake of the BOS incident and prior to the NH incident and the grounding.
Now that news reports are bringing light to the FAA's (and other regulatory bodies') practices on certification, I expect this is a partial "CYA" event for when they are called before the US Congress.
RickNRoll From Afghanistan, joined Jan 2012, 509 posts, RR: 0 Reply 174, posted (4 months 1 week 5 days 1 hour ago) and read 9933 times:
Quoting Pihero (Reply 171): The last sentence seems to me a bit harsh... unless the alerting / message / alerting levels and priority system is being looked after. Remember, in the initial press reports, the decision to divert and land in emergency wsqasn't ( professional opinion ) warranted by the merssages displayed... although, with hinsight, the crew was right.
It is quite possible they were instructed to do so by their company in the event of any battery anomalies.
kanban From United States of America, joined Jan 2008, 2500 posts, RR: 21 Reply 175, posted (4 months 1 week 5 days ago) and read 9920 times:
Quoting RickNRoll (Reply 174): It is quite possible they were instructed to do so by their company in the event of any battery anomalies.
You missed the point. the statement being referred to is:
"While airborne, the crew must continuously monitor the flight computer for battery related status messages, and land immediately if one occurs."[/quote] and refers to the conditions under which Boeing may conduct test flights.. It is not the company's text. Now that said, I am sure that any test flight plans/procedures would cover the same instructions anyway even if the FAA had not spelled it out... since that data is part of the purpose of the test
RickNRoll From Afghanistan, joined Jan 2012, 509 posts, RR: 0 Reply 176, posted (4 months 1 week 4 days 23 hours ago) and read 9920 times:
I was referring to the post by Pihero.
The last sentence seems to me a bit harsh... unless the alerting / message / alerting levels and priority system is being looked after. Remember, in the initial press reports, the decision to divert and land in emergency wsqasn't ( professional opinion ) warranted by the merssages displayed... although, with hinsight, the crew was right.
I think he is referring to the ANA emergency landing. It is possible the crew were complying with company directions on what actions to take in the case of a battery event.
sunrisevalley From Canada, joined Jul 2004, 4002 posts, RR: 4 Reply 177, posted (4 months 1 week 4 days 7 hours ago) and read 9825 times:
Any ideas how long it will be before the FAA declare themselves as satisfied and tell the NTSB to f.... off ?
Nothing that I have read suggests that there is proof that there was a probable chance that a fire in the battery box would become uncontained. Has an attempt been made to deliberately create a fire in the battery box under controlled circumstances to see what happens ?
strfyr51 From United States of America, joined Apr 2012, 488 posts, RR: 0 Reply 178, posted (4 months 1 week 4 days 5 hours ago) and read 9745 times:
Well, It seems I'm right, the FAA just granted Boeing the right to conduct test flights for the Lithium Ion Batteries On the B787. Boeing should get to the bottom of this "Mos-scosche" (Quickly) since their Butts are hanging out a couple of Yards.
ltbewr From United States of America, joined Jan 2004, 12365 posts, RR: 12 Reply 179, posted (4 months 1 week 4 days 1 hour ago) and read 9668 times:
My question is how these grounded 787's are being kept. I would assume there are procedures to cover engine openings, for example, but what is done short (1-2 months) and possibly long term (6 months +) to maintain them for returning them to the air when a fix is approved and installed?
most every airline has storage procedures for short mid and long term storage. (can't say all because I don't know)
At United we continue the #1 and #2 service checks on a Day based time schedule, no servicing is overlooked and the engines are run on schedule, only avionics Might suffer from lack of use, after all they're computers.
Caryjack From United States of America, joined May 2007, 265 posts, RR: 0 Reply 181, posted (4 months 1 week 3 days 11 hours ago) and read 9434 times:
Quoting ltbewr (Reply 179): My question is how these grounded 787's are being kept. I would assume there are procedures to cover engine openings, for example, but what is done short (1-2 months) and possibly long term (6 months +) to maintain them for returning them to the air when a fix is approved and installed?
I hate to say it but as far as the 787 program is concerned, storing unflyable 787s is the one task where is Boeing the unchallenged expert.
Thanks,
Cary
HAWK21M From India, joined Jan 2001, 31228 posts, RR: 58 Reply 182, posted (4 months 1 week 3 days 11 hours ago) and read 9400 times:
Quoting ltbewr (Reply 179): My question is how these grounded 787's are being kept. I would assume there are procedures to cover engine openings, for example, but what is done short (1-2 months) and possibly long term (6 months +) to maintain them for returning them to the air when a fix is approved and installed?
The AMM has a listed of Storage and preservation checklist to be adhered too.This frequency can be a weekly , forthnightly,monthly,3 monthly,6 monthly annually depending on the type.
they discuss micro fibers growing in (I assume) the electrolyte leading to problems. being a non chemist, it seems similar to those crystal growing kits I played with as a kid.. only more complex.
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 184, posted (4 months 1 week 12 hours ago) and read 8520 times:
Quoting kanban (Reply 183): they discuss micro fibers growing in (I assume) the electrolyte leading to problems. being a non chemist, it seems similar to those crystal growing kits I played with as a kid.. only more complex.
I've had problems with carbon whiskers in rf filters. They were from contamination during manufacturing. I'm not familiar with the ones in lithium batteries. They'd probably spot them on the ISS from the extreme level they take cell charge and discharge curve monitoring to, but I doubt if Boeing tracks them to that level.
It could be like the kids crystal kits. An irregularity or spot of contamination can give the crystals a place to spawn and grow.
okie From United States of America, joined Jul 2003, 2410 posts, RR: 3 Reply 185, posted (4 months 1 week 5 hours ago) and read 8281 times:
Quoting nomadd22 (Reply 184): They'd probably spot them on the ISS from the extreme level they take cell charge and discharge curve monitoring to, but I doubt if Boeing tracks them to that level
The 787 battery pack is 8 batteries in series with each battery having 6 cells in parallel. From what I understand and from looking at the pictures released by the NTSB is that they are only monitoring each battery and only controlling charge voltage when battery gets to near full charge to keep all batteries equal. So they are not going to the cell level for monitoring.
The linked yahoo article above also speaks of quality issues with contamination, folds, wrinkles & pinches within the cells between the plates and separator during manufacture.
The battery picture the NTSB had listed the separator at 25 microns thick. That is a pretty thin piece of material and I would guess easily damaged by a piece of dust, a wrinkle or folds in the plates or separator as indicated above especially when subject to vibration or handling of the battery pack
For perspective the oil filter in a car is rated at 33 microns and would let 25 micron sized particle go right on through.
Just a wild guess but I suspect the issue is going to be quality control at Yuasa, which is why I asked up thread about Thales using a different manufacturer for the cells for the battery pack.
prebennorholm From Denmark, joined Mar 2000, 6039 posts, RR: 55 Reply 186, posted (4 months 1 week 3 hours ago) and read 8257 times:
Quoting okie (Reply 185): The 787 battery pack is 8 batteries in series with each battery having 6 cells in parallel.
This is not correct, even if it could look like that on the ANA battery.
The Yuasa LVP65 cell has the an active internal unit which is almost one meter long, if stretched to full length. But it is folded in six layers to fit in the cell box.
There are no parallel cells in the 787 battery, only 8 cells in series.
It is quite normal practice to fold Li-Ion cells like the Yuasa LVP65. But they may also be rolled to the shape of cylinders like most - if not all - NiCad and NiMH batteries are.
Always keep your number of landings equal to your number of take-offs, Preben Norholm
Seat55A From New Zealand, joined Jan 2013, 31 posts, RR: 0 Reply 188, posted (4 months 5 days 18 hours ago) and read 7702 times:
Quoting okie (Reply 187):
The drawings, pictures, and CT scans show distintly 6 positive collectors and 6 negative collectors for each battery what is being called a cell.
The collectors have a fork-like shape, but you can see the media in between them is a continuous item that is accordion-folded. Three folds (rounded tops) and six long sides are showing in the perspective of the drawing.
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 189, posted (4 months 5 days 16 hours ago) and read 7675 times:
Quoting okie (Reply 187): The drawings, pictures, and CT scans show distintly 6 positive collectors and 6 negative collectors for each battery what is being called a cell.
Even if you were right, the pictures only show six points total, which would be three parallel cells. And, you're not right. Those triangles are just how they mount the connector. When you're building a cell as strong as those were suppose to be, you don't just connect straight to the tops of the anodes and cathodes.
strfyr51 From United States of America, joined Apr 2012, 488 posts, RR: 0 Reply 192, posted (4 months 4 days 3 hours ago) and read 7057 times:
just read today that Boeing is re-designing the lithium Ion Battery to make each cell isolated in an attempt to isolate
malfunctioning cells from other cells more than likely giving the cells more room in the case and placing a barrier between cells.
I don't know if this is going to work bu it damn sure can't Hurt
On another note?
Airbus is reverting to tried and tested nickel cadmium batteries for its A350 XWB family, following Boeing’s problems with lithium ion technology on the 787.
sweair From Sweden, joined Nov 2011, 1604 posts, RR: 0 Reply 193, posted (4 months 3 days 22 hours ago) and read 7003 times:
Quoting strfyr51 (Reply 192): Airbus is reverting to tried and tested nickel cadmium batteries for its A350 XWB family, following Boeing’s problems with lithium ion technology on the 787.
This is damn sure revealing!!
IMO Airbus has a choice that Boeing doesn't, they have not yet certified its batteries, why risk unnecessary hard certification when there is an easier route?
Boeing has no other choice than to stick with what they have, they cant have the aircraft grounded for a year.
B will do anything to prove their system safe to lift the grounding, FAA will feel the increasing pressure to lift that grounding despite NTSBs ongoing investigation a year from now.
B really have to show its customers the plane is safe, this will be even harder than the FAA IMO, they have a bad rep after all snags so far and one other serious incident could be too much for airlines, so the pressure is equal on Boeing IMO.
Quoting Kaiarahi (Reply 195): Quoting strfyr51 (Reply 192):Boeing is re-designing the lithium Ion Battery
I doubt it. Yuasa might be.
I'm sure they *both* are. I'm pretty sure that any redesign of the battery to better contain a failure of the individual cells is going to make the battery bigger and heavier, which means that the battery box will be getting bigger and stronger...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
I'm not sure the box is a Boeing design.. Boeing is providing the space envelope but the battery pack is a vendor designed LRU, whether that is a Thales' design or Yuasa's I'm not sure, however Thales will be involved to ensure the interfaces match with the distribution system.
WingedMigrator From United States of America, joined Oct 2005, 2031 posts, RR: 56 Reply 199, posted (4 months 2 days 23 hours ago) and read 6683 times:
nomadd22 From United States of America, joined Feb 2008, 1578 posts, RR: 0 Reply 200, posted (4 months 2 days 16 hours ago) and read 6563 times:
Quoting WingedMigrator (Reply 199): Quoting prebennorholm (Reply 197):
A 14kWh battery would be a 500 lbs monster.
So an 85 kWh battery (such as is found in the Tesla Model S) would be a 6000 pound monster. Amazing.
Interesting math. How do you get a battery 6 times the capacity weighing 12 times as much?
As it is, the Tesla 85kwh pack runs about 1400 pounds. The 787 Lithium cells probably weigh less that half the 63 pound weight I see posted. I'm guessing the boxes account for a little more than half the unit weight.
bonusonus From United States of America, joined Nov 2009, 398 posts, RR: 0 Reply 201, posted (4 months 2 days 8 hours ago) and read 6400 times:
Quoting prebennorholm (Reply 197): Nominal cell voltage is 3.7V, therefore 8 * 65Ah * 3.7V = 1.924kWh - or about 2kWh.
Thanks for the clarification. That makes more sense. Strangely, I read an article that states that typical energy drawdown to start an APU is 15kWh (http://batteryuniversity.com/learn/article/batteries_for_transportation_aerospace about halfway down). This must be an order of magnitude off then, right?
prebennorholm From Denmark, joined Mar 2000, 6039 posts, RR: 55 Reply 202, posted (4 months 2 days 4 hours ago) and read 6515 times:
Quoting nomadd22 (Reply 200): The 787 Lithium cells probably weigh less that half the 63 pound weight I see posted. I'm guessing the boxes account for a little more than half the unit weight.
Each cell is 2,750g, so 8 cells without box etc. is exactly 22kg or 48lbs and 7oz.
76.9% is little more than half, so yes, you are right...
Always keep your number of landings equal to your number of take-offs, Preben Norholm
"Boeing will propose to regulators as early as this week a short-term fix to bolster the 787’s defenses in case of battery fires like those that have kept the jet grounded for the past month.
The goal is to get the planes flying passengers again, according to multiple sources with knowledge of the matter, while Boeing works on a comprehensive redesign of the lithium-ion battery system that could take nine months or more to implement."
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 205, posted (3 months 4 weeks 1 day 12 hours ago) and read 5837 times:
Boeing is also evidently looking into increasing the spacing between the batteries to improve cooling and to prevent short-circuits from cascading to adjacent batteries. And Kiyoshi Kanamura, a professor at Tokyo Metropolitan University who has conducted research with several Japanese battery makers, suggested that ceramic plates be installed between the cells.
bellancacf From United States of America, joined May 2011, 121 posts, RR: 0 Reply 206, posted (3 months 4 weeks 1 day 7 hours ago) and read 5724 times:
It's good to hear that those cells won't be pressed against each other (albeit with partition), as the recent diagram from Boeing makes it appear that the current geometry does little or nothing to prevent heat from reaching the neighboring cells. In fact, if you wanted to design a battery to retain as much heat as possible, the current design would be a good candidate. (What _were_ they thinking of?)
JoeCanuck From Canada, joined Dec 2005, 5135 posts, RR: 29 Reply 207, posted (3 months 4 weeks 1 day ago) and read 5622 times:
Through this entire ordeal, it's easy to forget, (except for the diehard tin hatters), that the crappy containment of the original batteries, actually worked surprisingly well. Those thin walls contained the fire, (which was probably very bloody hot), and most of the electrolyte. The fire raged on, (or whatever), until most of the electrolyte was burned off and no significant damage was done to the plane.
That's not to take away the very real fear that comes with smoke and stink wafting through an airliners cabin in flight. Whether or not damage will be done is mostly irrelevant to the people truly believing they are living their last moments.
I have no doubt more robust containment will be a significant part of the recertification program but Boeing and the FAA have the unenviable task of trying to certify batteries which have been shown to burn up...and no amount of containment will satisfy the most rabid doubters.
I really hope Boeing finds a way to squeeze a NiCd pack into the electronic bays. Nothing says peace of mind to the punters like technology proven by decades of reliable service. Take the bullet, say LI-ion technology isn't quite mature enough and go low tech. I have no doubts that the charging system of the 787 can be made to handle NiCd's with very little in the way of modifications.
Do whatever it takes to get this battery stuff behind them and get on with the business of making planes that airlines can fly.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 208, posted (3 months 4 weeks 14 hours ago) and read 5423 times:
Quoting JoeCanuck (Reply 207): I have no doubt more robust containment will be a significant part of the recertification program but Boeing and the FAA have the unenviable task of trying to certify batteries which have been shown to burn up...and no amount of containment will satisfy the most rabid doubters.
I am of the opinion that the current batteries won't be in service by the end of the year unless it is definitively proven that the cause of both thermal runaway events was due to either incorrect wiring or a manufacturing defect in the batteries themselves that can be eliminated.
The new, safer containment system should be enough to get the 787 back into revenue service, but new, safer batteries will have to be installed in the new, safer containment system to truly restore confidence and that appears to be the track Boeing is suggesting.
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 209, posted (3 months 4 weeks 9 hours ago) and read 5284 times:
Should be simple enough to test-build a ground mockup of both E&E bays, and intentionally short out a cell, and watch what happens Oh, and it would be worst-case (on the ground, no pressure differential...).
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
CALTECH From Poland, joined May 2007, 1603 posts, RR: 22 Reply 210, posted (3 months 3 weeks 4 days 8 hours ago) and read 4701 times:
Quoting zeke (Reply 45): In brand A aircraft I am only used to seeing batteries receiving a short charge in flight and then disconnecting from the charge (to bring the battery back up to its nominal voltage range). Most of the time they do not receive a charge, they are simply connected to the DC bus, however the DC bus is normally powered by normal power sources (AC BUS and TR to the DC BUS) and taking next to nothing from the batteries.
The 787 manual shows the 28 Vdc bus being normally powered by the 235 Vac bus via a power converter. I read the 787 FCOM on this part, it lacks any real depth to tell a lot of detail on the system. It does not show any input bus to charge the APU battery. I wonder if the main battery is continuously being charged, or if it has smarts in the system so it is only charged when required.
Think you have it right. It seems that on the 787, after takeoff, gear up or a few minutes pass and the MainBatteryRelay opens to isolate the Main Battery and HotBattBus from the CaptInstrumentBus. The Main Battery also seems to power flight critical electric power if all AC power is lost until the RAT is deployed.
But then reading that on the 787, main battery charger and APU battery charger will charge the main and APU battery respectively when these conditions are met, 32.2 volts or less for the battery open circuit voltage, or the F/OInstrumentBus is energized this is for the APU battery only, or if the MBR is open, the Main Battery Charger will be charge if volts are below the threshold voltage. After takeoff the MBR is energized open. And if correct signals are received from the battery monitoring unit. Think you're right that the Main and APU Batteries will only receive a charge when needed, when the voltage drops below 32.2. How often that happens in flight ? Don't have a answer for that, if it happens at all. Would have to monitor the electrical page to see what goes on during flight.
rcair1 From United States of America, joined Oct 2009, 950 posts, RR: 25 Reply 211, posted (3 months 3 weeks 4 days 5 hours ago) and read 4604 times:
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Quoting Stitch (Reply 208): The new, safer containment system should be enough to get the 787 back into revenue service, but new, safer batteries will have to be installed in the new, safer containment system to truly restore confidence and that appears to be the track Boeing is suggesting.
I share this opinion - but I have no data to support it...
BTW - the civ thread has gone seriously off into the weeds again... oh well.
okie From United States of America, joined Jul 2003, 2410 posts, RR: 3 Reply 212, posted (3 months 3 weeks 4 days 4 hours ago) and read 4605 times:
Quoting Stitch (Reply 208): The new, safer containment system should be enough to get the 787 back into revenue service, but new, safer batteries will have to be installed in the new, safer containment system to truly restore confidence and that appears to be the track Boeing is suggesting
I am afraid you are correct.
My guess at this point is that there is an issue with the battery cells themselves, either design or QC. In any case it appears that whatever final test procedures that the manufacturer is using is not finding cells that seem to be failing early in their life expectancy.
The concept of the containment (battery box) is for that one in 10 million chance of an cell failure, not and active battery cell incinerator.
rcair1 From United States of America, joined Oct 2009, 950 posts, RR: 25 Reply 213, posted (3 months 3 weeks 3 days 14 hours ago) and read 4415 times:
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Quoting okie (Reply 212): The concept of the containment (battery box) is for that one in 10 million chance of an cell failure, not and active battery cell incinerator.
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I know that in laptop batteries, there are fuses (tiny pieces of metal) that are designed to melt away if a short happens. The battery pack needs replacement if the fuse ever gets blown...but the idea is that the fuse blows before you get a thermal runaway on a LiIon battery.
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