Tech/Ops Discussion Of The 787 Grounding

Aviaponcho · Tue Jan 29, 2013 8:54 pm

Sorry, I missed it
I would have pointed the very same slide by the way !

seat55a · Tue Jan 29, 2013 10:02 pm

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 · Wed Jan 30, 2013 12:46 am

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.

[Edited 2013-01-29 16:58:22]

tdscanuck · Wed Jan 30, 2013 1:50 am

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...

Tom.

Okie · Wed Jan 30, 2013 1:56 am

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.

Okie

JHwk · Wed Jan 30, 2013 2:30 am

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 · Wed Jan 30, 2013 2:52 am

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.

Welcome!

Tom.

seat55a · Wed Jan 30, 2013 3:32 am

New York Times reports there was history of 787 battery issues at NH

http://www.nytimes.com/2013/01/30/bu...battery-ills-before-the-fires.html

Also one or two new things about the incident flight and the Q C procedures.

(edit I see someone posted this already in the Civ Av thread)

[Edited 2013-01-29 19:39:47]

JoeCanuck · Wed Jan 30, 2013 7:24 am

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.

Quoting ferpe (Reply 90):

Thanks for that.

AirlineCritic · Wed Jan 30, 2013 7:58 am

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 · Wed Jan 30, 2013 9:08 am

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.

http://www.pprune.org/tech-log/505695-787-batteries-chargers.html

Caryjack · Wed Jan 30, 2013 11:35 am

Quoting okie (Reply 104):
the SCR in the charger

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.

Welcome!

Thanks,

Cary

tdscanuck · Wed Jan 30, 2013 2:26 pm

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).

Quoting AirlineCritic (Reply 109):
This was no freak occurrence, it was a real problem.

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.

Tom.

litz · Wed Jan 30, 2013 7:20 pm

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 · Wed Jan 30, 2013 7:52 pm

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 · Wed Jan 30, 2013 8:40 pm

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 · Wed Jan 30, 2013 8:51 pm

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;

http://www.mpoweruk.com/index.htm

nomadd22 · Wed Jan 30, 2013 9:29 pm

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.

It's not the only alternative. I'm going to cheat and copy a post from uncivil av.
http://www.flightglobal.com/news/art...ttery-fundamentally-unsafe-381627/

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 · Wed Jan 30, 2013 10:01 pm

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.

That would be interesting. I'll watch for it. To help -
Here is the data sheet that is, reportedly, on the cell inside the 787 battery. The 787 has 8 of these LVP65's
http://www.s399157097.onlinehome.us/SpecSheets/LVP10-65.pdf

KELPkid · Wed Jan 30, 2013 10:20 pm

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...

JoeCanuck · Wed Jan 30, 2013 10:33 pm

Quoting nomadd22 (Reply 117):
It's not the only alternative.

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 · Wed Jan 30, 2013 11:41 pm

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.

mham001 · Wed Jan 30, 2013 11:53 pm

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

Charge temperature: 0-45C
Operating temperature: -20-55C

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,

[Edited 2013-01-30 15:57:59]

JoeCanuck · Thu Jan 31, 2013 1:14 am

Quoting mham001 (Reply 122):

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

[Edited 2013-01-30 17:17:13]

ferpe · Thu Jan 31, 2013 5:39 am

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:

http://www.king5.com/video/featured-...87-battery-problems-189115821.html

"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. "

This ideas was also discussed here upthread.

Aviaponcho · Thu Jan 31, 2013 8:29 am

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...

Have a good day

dynamicsguy · Thu Jan 31, 2013 10:38 am

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 · Thu Jan 31, 2013 11:00 am

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 · Thu Jan 31, 2013 3:31 pm

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 · Thu Jan 31, 2013 4:02 pm

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.

Okie

Stitch · Thu Jan 31, 2013 4:57 pm

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 · Thu Jan 31, 2013 5:17 pm

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.

[Edited 2013-01-31 09:25:47]

Aviaponcho · Thu Jan 31, 2013 8:46 pm

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

Thank you

[Edited 2013-01-31 13:24:11]

strfyr51 · Thu Jan 31, 2013 9:09 pm

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 · Thu Jan 31, 2013 9:25 pm

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 · Thu Jan 31, 2013 9:52 pm

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 · Fri Feb 01, 2013 12:55 am

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 · Fri Feb 01, 2013 3:10 am

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.

Tom.

Okie · Fri Feb 01, 2013 3:59 am

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.

Okie

kanban · Fri Feb 01, 2013 8:29 am

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 ?

Aviaponcho · Fri Feb 01, 2013 9:17 am

Quoting Stitch (Reply 134):

Thank you Stitch

All right, but then can this vent still be use for venting the avionic bay ? You still need to vent the forward EE bay don't you
?

zeke · Fri Feb 01, 2013 9:17 am

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.

strfyr51 · Fri Feb 01, 2013 5:07 pm

Quoting okie (Reply 138):

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 · Fri Feb 01, 2013 5:31 pm

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 · Fri Feb 01, 2013 7:55 pm

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 · Fri Feb 01, 2013 9:26 pm

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 · Sat Feb 02, 2013 1:13 am

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.

Tristarsteve · Sat Feb 02, 2013 2:15 pm

Quoting dalmd88 (Reply 146):
Every other Boeing works this way.

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 · Sat Feb 02, 2013 5:20 pm

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.

NS

Okie · Sat Feb 02, 2013 6:52 pm

Quoting strfyr51 (Reply 142):

Thales didn't build or design that particular Lithium Ion Battery, the Company is GS Yuasa out of Japan

I am aware that Thales out sourced the battery to GS Yuasa.
The battery carries a Thales part number on every picture Okie has seen.

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.

I guessing you can change batteries in other aircraft from different manufactures without a whole lot of hoops to jump through.

Okie

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