Quoting wjcandee (Reply 177): Not necessarily, given that the article says that some ran down or locked out because mechanics incorrectly disconnected them. Sounds like this may be in part a user problem.

A normal battery doesn't need that special handling. A normal battery doesn't need to be returned to the manufacturer if it goes flat. These batteries need this special handling for safety reasons, but is it worth the trouble. Once again, I think the A350 team will have more to chew on.

Quoting DocLightning (Reply 6): Quoting liftsifter (Reply 2): Has John Leahy made a comment at all about the grounding and how it may affect the A350 program? Even Mr. Leahy is smart enough to know to keep his mouth shut.

"Even Mr. Leahy" ? You think he's an idiot ?

Quoting AirlineCritic (Reply 7): And you can rest assured that none of them are gloating about it, because they know that if they are not careful, their new A350 might be next.

You mean, not like this ?

http://www.youtube.com/watch?v=9WKdI-KVWtc

Quoting BoeingVista (Reply 173): Quoting phxa340 (Reply 165):If you didn't cherry pick the article to fit your agenda is also mentions Boeing and ANA didn't report the battery changes because they were a reliability concern NOT a safety concern. If anything - it proves that the safeguards Boeing installed were highly successful with the two notable exceptions being the JL and NH birds recently. The Seattle Times article says 100 - 150 batteries failed fleet wide, I don't see how Boeing can have 100 plus Li-ion batteries plus multiple fail knowing that failed Li-ion batteries can cause fires, on a fleet of under 50 aircraft and not consider this a safety issue. If they did not see this as a safety issue then all the better that this is now being looked at by the FAA and NTSB as it clearly DID turn out to be a safety issue.

I'm with Boeingvista on this, Boeing and ANA may have thought it to be a reliability issue, I can live with that, but with the 2 major battery incidents, its become a safety issue which the FAA has taken out of Boeings hands.

Quoting RickNRoll (Reply 174): A lot of them havn't failed, if they just get to 15% capacity they lock themselves out, and have to be returned to the manufactuer to be reset and recharged safely. It appears that the battery demands of a plane on the ground will drain them more than anticicpated.

If they are getting to that 15% of charge regularly and having to be replaced, something needs to be addressed to make it a rare occurance rather than a regular one. Same goes if they are needing to be replaced due to operator error when disconecting. Maybe i'm oversimplyfying my thoughts, I don't work in the industry, but it seems to me long term, replacing batteries on a regular basis due to these issues needs to be engineered out. Does the battery being drained to about 16-20% charge on a regular basis have any affect on it? (i.e just above the cut off point)

Quoting AeroWesty (Reply 180): Quoting BoeingVista (Reply 179):You prevent deaths by investigating unexpected failures and if 100 failed 40kg Li-ion batteries on an aircraft doesn't ring alarm bells knowing the power that they can unleash when they go bad then you are in the wrong business.What would be accomplished looking for a fire threat when the reason for their return was "battery disconnected improperly" or "battery allowed to run down below spec", or "battery past expiration date"? How are those situations threats to aviation safety as standalone incidents?

Those incidents may not be threats to aviaton as standalone incidents, but put them altogether with the 2 major incidents and they become something that needs to be looked into. 100-150 battery failures/cut offs/operator errors on a fleet of 60-70 aircraft seems alot me. Does anyone know how long the batteries are supposed to be in use for before removal and overhaul?

Quoting 7BOEING7 (Reply 181): "Most of the batteries were returned because they had run down so far that a low-voltage cutout was activated"Which part of this do you not understand??? Sounds like it's operator error combined with improper design specs -- expensive but not catastrophic.

Your post come across as dismissive of the returned batteries being important in the investigation. Low voltage is one of the causes of thermal runaway as far as I have learnt on these threads. If batteries are being returned on a regular basis because they have cut off by the low voltage, and then we had 2 major incidents of thermal runaway, returned batteries for this reason very much become important. You have said it sounds like operator error or improper design spec, it also sounds like it could be a problem in how the plane is using the batteries, in that it drains them to the cut off point on a regular basis. Weather it is a deisgn problem that needs to be fixed or a process issue that nees to be changed is what needs to be established. In the long run airlines won't put up with it I wouldn't have thought.

Quoting 7BOEING7 (Reply 181): Quoting BoeingVista (Reply 179): You prevent deaths by investigating unexpected failures and if 100 failed 40kg Li-ion batteries on an aircraft doesn't ring alarm bells knowing the power that they can unleash when they go bad then you are in the wrong business. "Most of the batteries were returned because they had run down so far that a low-voltage cutout was activated"

This information is a hint that the BMS is designed wrongly. If a large number of batteries is killed by discharging them too much, the charging/discharging system is not worth much. It is the chargers responsibility to always maintain safe upper and lower voltage limit over any cell. There is no other responsibility for ruined batteries by the hundreds than crappy chargers.

If the low voltage condition is not handled properly by the BMS, undetected damages to cells will be inevitable which make the charging and further use of the battery unpredictable. A single damaged cell might strike back the next time a charge run is made.

Even RC modellers have enormous low voltage detection gear to never unload the battery below certain limits. The considered accuracy goes down to millivolts...

Quoting JoeCanuck (Reply 182): That, if it worked, wouldn't solve the certification problem since it would have to be tested and proven as much as any other design, and probably more than going to battery types already proven in airline service.

Do you think there will be a solution without any certification problem? I expect huge certification efforts at this point. Regardless of the solution, that will be chosen.

Quoting JoeCanuck (Reply 182): Isolating cells still doesn't prevent any single cell from catching fire which is what the FAA is looking for. They want a 0% chance of any cell catching fire...ever...which may not be achievable since any battery of any type can catch fire but there are certainly safer types than the current ones.

The main point Elon Musk has raised are the small number of large cells. A larger number of smaller cells can be operated safely even in close proximity. The aspect that is unique on the 787 are the large cells and not the tight cell layout.

Quoting seahawk (Reply 186): I would say it is not uncommon for a new technology to have some problems at the start.

The dimension of the problem is uncommon. Including the grounding verdict.

Quoting JerseyFlyer (Reply 196): Intuitively this makes sense. An explanation from Boeing for their choice of eight large cells when presumably they discounted options comprising larger numbers of smaller cells would be of interest.

I agree.

Quoting BoeingVista (Reply 198): Over discharge of a Li-ion battery can lead to it short circuiting and that can lead to thermal runaway, it does not need to be recharged to be potentially dangerous. So under voltage can be as dangerous as over voltage.

Absolutely.

Quoting AeroWesty (Reply 199): When you say "over discharge", is your meaning discharging too quickly or discharging below a certain value, or both?

Both.

Below a certain voltage the cells simply will be destroyed and never useable again to store any meaningfull capacity.

And second, batteries have a C-value which is defined as follows: current that discharges the battery in one hour divided by the max. discharging current. This tells us how quick a battery may be discharged. E.g. 20C means that I might draw as much current, that after 60 minutes / 20 it (= 3 Minutes) it would become empty.

Quoting 7BOEING7 (Reply 181): "Most of the batteries were returned because they had run down so far that a low-voltage cutout was activated"

The article also says that "The frequency of battery failures reflects issues with the design of the electrical system around the battery, said the person on the 787 program."

Just for clarification, what is the battery in question being used to power? I thought I read earlier that it was a back-up supply for the cockpit instruments. If true then that suggests it isn't being called on very often (i.e. drained). However if, as someone pointed out, the battery is used to power systems while the plane is inactive on the ground then it begs the question, shouldn't the plane hooked up to ground power when its on the ground?

Apologies if this has been done to death already.

Quoting ncfc99 (Reply 202): Those incidents may not be threats to aviaton as standalone incidents, but put them altogether with the 2 major incidents and they become something that needs to be looked into.

I don't see where I've ever denied that. BoeingVista still hasn't made his case for why these singular incidents of batteries running down while the other generators were idle somehow presented an imminent threat to aviation safety, other than saying that people are "missing the obvious", without stating what that "obvious" is. He needs to state that in clear terms, without playing '20 questions', so his argument can be looked at and evaluated. Wouldn't you agree?

Quoting rheinwaldner (Reply 203): Below a certain voltage the cells simply will be destroyed and never useable again to store any meaningfull capacity.

Great. Understood already. Was that happening in flight other than on the ANA incident where the emergency landing was made? My understanding was that was happening on the ground, with those batteries pulled. Correct me at any point you'd like. I'm truly trying to understand why folks keep saying that these singular incidents regarding replaceable parts presented a problem as they occurred.

Quoting sweair (Reply 8):

Quoting sweair (Reply 8): If a battery or charging system fault can be identified and a slightly enhanced containment put into place, the plane should fly in 4-6 months, if not sooner, at least as a temporary measure for current frames.

4-6 Months? If you seriously believe that, it's time to short Boeing stock. They gotta get this thing flying a lot sooner than that.

Quoting AeroWesty (Reply 206): I don't see where I've ever denied that. BoeingVista still hasn't made his case for why these singular incidents of batteries running down while the other generators were idle somehow presented an imminent threat to aviation safety, other than saying that people are "missing the obvious", without stating what that "obvious" is. He needs to state that in clear terms, without playing '20 questions', so his argument can be looked at and evaluated. Wouldn't you agree?

I did and you replied to it.

Quoting BoeingVista (Reply 198): Over discharge of a Li-ion battery can lead to it short circuiting and that can lead to thermal runaway, it does not need to be recharged to be potentially dangerous. So under voltage can be as dangerous as over voltage.

The batteries run down until they get to a damaged state ie, need replacement.

A battery that has rundown into an under volt condition is potentially at risk from a thermal runaway meltdown what ever the state of the generators.

By over discharge this may mean to much power drained, under volt, or discharged too quickly

It should be obvious by thread 6 that Li-ion batteries are potentially dangerous and any pattern of major faults is worth investigating.

100-150 failed batteries and multiple failed chargers is surely a symptom of wider issues with the 787's electrical system, and really should have prompted Boeing to do something but it didn't do anything that we know about apart from keep issuing replacement batteries; after 150 incidents I would suggest they cease to be singular events and become a pattern.

The NTSB agree that these failed batteries are something that needs investigating and have added it to their investigation having been belatedly informed of this by Boeing.

The NTSB have not ruled out an under volt condition as being the source of either battery meltdown.

This thread is so long it is hard to know what has and has not been reported.

I wondered whether this recent article had been posted - I could not see it.

Seems fairly fundamentsal as a non expert.

http://www.flightglobal.com/news/art...ttery-fundamentally-unsafe-381627/

Quoting BoeingVista (Reply 208): 100-150 failed batteries and multiple failed chargers is surely a symptom of wider issues with the 787's electrical system, and really should have prompted Boeing to do something but it didn't do anything that we know about apart from keep issuing replacement batteries; after 150 incidents I would suggest they cease to be singular events and become a pattern.

And my point is that a lot of the incidents were due to mishandling/operator error, and you're using this 100-150 headline number as all encompassing, as has already been pointed out to you by more than folks than me.

What you need to establish is how many batteries drained at a dangerous enough rate, independent of human interference, that it should have alerted someone, anyone, that there was an imminent danger to flight safety prior to the JAL and ANA incidents. If you can do that, I'm on board. If you can't, I'll have to write it off to someone bleating 'BatteryGate'.

Fair enough?

Quoting AeroWesty (Reply 206): Quoting ncfc99 (Reply 202):Those incidents may not be threats to aviaton as standalone incidents, but put them altogether with the 2 major incidents and they become something that needs to be looked into. I don't see where I've ever denied that. BoeingVista still hasn't made his case for why these singular incidents of batteries running down while the other generators were idle somehow presented an imminent threat to aviation safety, other than saying that people are "missing the obvious", without stating what that "obvious" is. He needs to state that in clear terms, without playing '20 questions', so his argument can be looked at and evaluated. Wouldn't you agree?

Maybe i'm being dumb but I can follow Boeingvista's train of thought (maybe wrongly), but not yours. I'm not understanding why you need each battery failure to be seen as a singular incident. A few failures (say 10 or so) I could understand being classed as singular incidents, but 100-150 battery failures and 2 major failures, need to be investigated to see if there is a common failure of some type, be it battery design of manufacturing fault, charger or charging system fault or many other number of issues I don't have the inteligence to understand. I would agree, a statement of clear terms is far more preferable so my limited interlect can grasp the problems in hand.

Quoting AeroWesty (Reply 206): Quoting rheinwaldner (Reply 203):Below a certain voltage the cells simply will be destroyed and never useable again to store any meaningfull capacity. Great. Understood already. Was that happening in flight other than on the ANA incident where the emergency landing was made? My understanding was that was happening on the ground, with those batteries pulled. Correct me at any point you'd like. I'm truly trying to understand why folks keep saying that these singular incidents regarding replaceable parts presented a problem as they occurred.

I'm trying to understand why alot of singular failures of the same component(I understand not the same failures) didn't present itself as an issue. When the JAL bird had its issue after over 100 other battery issues, I would hope alarm bells started ringing at that point, if they hadn't done so before. Does anyone know if the FAA knew about the previous 100+ issues, so that is why the launched the reveiw?

Quoting ncfc99 (Reply 211): I'm trying to understand why alot of singular failures of the same component(I understand not the same failures) didn't present itself as an issue. When the JAL bird had its issue after over 100 other battery issues, I would hope alarm bells started ringing at that point,

Okay, real simple terms. Line up 100 blenders on your kitchen table. I take a sledgehammer to 95 of them and make them inoperable (operator error). Over the course of the following year, 5 go belly-up on their own for no apparent reason that you can determine immediately. Could be a loose connection, could be a bad plug, could be anything.

Can you say that all blenders are inherently bad? Would you report that because you had 100 non-functioning blenders on your hands that that would justify a product recall? Of course not. You can't look at the headline number. You have to evaluate what you're dealing with.

Quoting AeroWesty (Reply 210): And my point is that a lot of the incidents were due to mishandling/operator error, and you're using this 100-150 headline number as all encompassing, as has already been pointed out to you by more than folks than me.

http://www.defense-aerospace.com/art...ttery-ills-before-ana-failure.html

Not an expert but at least with ANAs battery issues it isn't clear to me from this article their problems are due to mishandling/operator error.

Quoting trex8 (Reply 213): Not an expert but at least with ANAs battery issues it isn't clear to me from this article their problems are due to mishandling/operator error.

Okay, I read that link. It's incomplete. You have to read the Seattle Times article in reply #169 and read the next few replies to get the full gist of the battery replacement issue.

Quoting BoeingVista (Reply 208): 100-150 failed batteries and multiple failed chargers is surely a symptom of wider issues with the 787's electrical system

Did you read either article? At All!?

There were not "100 to 150 failures," there were that many replacements.
-- Some were discharged to their lower safety limit, and automatically "bricked" themselves to prevent damage
-- Some were expired
-- Some were in fact faulty

Merely repeating a convenient but incorrect number makes one sound hysterical and misinformed.

Quoting ncfc99 (Reply 211): I'm trying to understand why alot of singular failures of the same component(I understand not the same failures) didn't present itself as an issue.

The answer is in the question. If you have a bunch of issues which aren't directly related, it is difficult to determine a pattern.

[Edited 2013-01-30 05:41:44]

[Edited 2013-01-30 05:45:57]

Looks like Boeing is going full steam ahead  

"It said it plans to manufacture between 635 and 645 Dreamliners by year-end"

"Overall, Boeing says it plans to produce almost 61,000 airplans in 2013."

http://www.usatoday.com/story/money/...ing-earnings-787-forecast/1876605/

Quoting Reply 207): 4-6 Months? If you seriously believe that, it's time to short Boeing stock. They gotta get this thing flying a lot sooner than that.

aero.de and airliners.de are both running today an article from DPA. There it says: 'In the industry, some consider a delay of one to two years for possible.'

http://www.airliners.de/technik/prod...boeing-droht-teures-erwachen/28923
http://www.aero.de/news-16764/Alptra...-Boeing-droht-boeses-Erwachen.html

Quoting art (Reply 192): The lithium ion batteries installed on the Boeing 787 are inherently unsafe, says Elon Musk, founder of SpaceX and owner of electric car maker Tesla. "Unfortunately, the pack architecture supplied to Boeing is inherently unsafe," writes Musk in an email to Flightglobal. "Large cells without enough space between them to isolate against the cell-to-cell thermal domino effect means it is simply a matter of time before there are more incidents of this nature," he adds. 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.

I think he might be on to something. With about 2,400 Tesla Roadsters on the road I can't find a single report of a fire involving their li-ion battery. The only Tesla fire threat I could find was a recall in 2010 because of a fire in the back-up lead-acid battery.
http://wheels.blogs.nytimes.com/2010...ing-439-roadsters-for-fire-hazard/

It sounds to me like a battery redesign would be a better solution than switching to an entirely different type of battery or power source.

Quoting AeroWesty (Reply 206): Was that happening in flight other than on the ANA incident where the emergency landing was made? My understanding was that was happening on the ground, with those batteries pulled.

I have no idea.
A starting point would be to check the use cases in what situations current is drawn from the batteries. In a sense the low voltage detection should not even have to work frequently, because a low voltage situation means that the battery capacity is not enough for demand that can happen. It indicates a battery-dimensioning problem.

So too low voltage should normally never happen. If it happens, the BMS could safe the batteries life and cut off the load from the battery. Or it could extend discharging of the battery minimally by not cutting of the load. But that would ruin the battery. And would not really help the power consumer much, because the capacity that can be drawn between a safe minimal voltage and ruining the battery is minimal.

So as a summary: 100 destroyed batteries because of over-discharging indicate a poor charger design and a wrongly dimensioned battery.

Quoting flood (Reply 216): "Overall, Boeing says it plans to produce almost 61,000 airplans in 2013."

That's a mistake right??   

Unless we're talking toy planes   

Quoting AeroWesty (Reply 212): Okay, real simple terms. Line up 100 blenders on your kitchen table. I take a sledgehammer to 95 of them and make them inoperable (operator error). Over the course of the following year, 5 go belly-up on their own for no apparent reason that you can determine immediately. Could be a loose connection, could be a bad plug, could be anything.

Not a good comparison in my opinion. A) thats sabotage, not operater error, B) I expect better than a 5% failure rate of the batteries used in aviation.

As far as I know, we don't know the different failure mode quantities. Even if it is less than 5% battery failure rate, As far as I know from reading these threads, it sould be far less than that, i.e 1 in a million rather than 1 in 20.

Quoting AeroWesty (Reply 214): Quoting trex8 (Reply 213):Not an expert but at least with ANAs battery issues it isn't clear to me from this article their problems are due to mishandling/operator error. Okay, I read that link. It's incomplete. You have to read the Seattle Times article in reply #169 and read the next few replies to get the full gist of the battery replacement issue.

The whole gist of the article tells me that the problem is far less operater error and more an issue with the plane or batteries themselves. Of the ten ANA batteries replaced, none appear to be operater error. JAL mention battery 'irregularities'. The gist tells me operater error is a small issue to deal with.

Quoting rheinwaldner (Reply 219): So as a summary: 100 destroyed batteries because of over-discharging indicate a poor charger design and a wrongly dimensioned battery.

I missed where there were 100 destroyed batteries, only that those which had been discharged past a certain level had to be returned as their safety interlock had made them inoperable.

This could in fact be operator error in some cases; you want to be able to use the very last watt-hour of power in an emergency, but you want to avoid doing so during ground ops. Training perhaps?

Quoting rheinwaldner (Reply 219): So as a summary: 100 destroyed batteries because of over-discharging indicate a poor charger design and a wrongly dimensioned battery.

You have to go back and read the Seattle Times article. It wasn't 100 destroyed batteries because of over-discharging. Many, many were disabled simply due to mechanics disconnecting the batteries improperly.

How many times do folks have to repeat this for people to get it?

Quoting AeroWesty (Reply 210): What you need to establish is how many batteries drained at a dangerous enough rate, independent of human interference, that it should have alerted someone, anyone, that there was an imminent danger to flight safety prior to the JAL and ANA incidents. If you can do that, I'm on board. If you can't, I'll have to write it off to someone bleating 'BatteryGate'. Fair enough?

Nope. Why should I bother, you can come to the realisation that there is a widespread problem and come on board or not in your own sweet time, no skin off my nose. You can put Batterygate right next to GroundedbytheFAAgate, these aren't conspiracy theories these are real world things actually happening in real life before your very eyes.

Quoting RottenRay (Reply 215): There were not "100 to 150 failures," there were that many replacements. -- Some were discharged to their lower safety limit, and automatically "bricked" themselves to prevent damage - FAILURE -- Some were expired - Shelf life of less than a year? I'm calling BS and FAILURE on this too -- Some were in fact faulty - FAILURE

You really make me LOL; you contend that bricked batteries are not failed? or faulty batteries are not failed?

What number of batteries do you think 'failed' give me a number or are you of the opinion that until a statement comes down from a mountain in Chicago written on stone tablets that nothing is to be believed so none failed?

Quoting RottenRay (Reply 215): Merely repeating a convenient but incorrect number makes one sound hysterical and misinformed.

Yawn, I'm very much better informed than you are; you can check the record if you wish.

Quoting RottenRay (Reply 215): Quoting ncfc99 (Reply 211):I'm trying to understand why alot of singular failures of the same component(I understand not the same failures) didn't present itself as an issue. The answer is in the question. If you have a bunch of issues which aren't directly related, it is difficult to determine a pattern.

But to my mind they are directly linked by one thing, the batteries. What is making the batteries fail or have to be replaced is the big question, IMHO.

Quoting RottenRay (Reply 215): There were not "100 to 150 failures," there were that many replacements. -- Some were discharged to their lower safety limit, and automatically "bricked" themselves to prevent damage -- Some were expired -- Some were in fact faulty

OK, of the replaced batteries-

--If they are being discharged to the level that they 'brick' themselves, I have to ask why they are getting that discharged so regularly (ANA stated 5 out of 10 had shown 'unexpectedley low charge'. I would have thought 'bricking' due to low charge should be a rare event.
--Battries replaced due to being expired is expected. I asked further up the thread, how long are the expected to last before removal and overhaul?
--Some faulty batteries on a fleet of 50 aircraft in commercial use (100 batteries) I would expect the number of failures to be quite low at this point. Its not new tech as such, its new in an aircraft. Reliability of the batteries should be good, should it not?

Quoting BoeingVista (Reply 162): Boeing knew of problems with the 787 batteries, ANA changed 10 batteries between May and December 2012

New aircraft change *far* more parts than that (in number terms). You can't lump economic problems (which is what part replacements without safety effects are) with safety problems (e.g. fires) without additional datal

Quoting BoeingVista (Reply 162): This fills in a few more blanks that have been speculated about, yes there were widespread issues with the 787 batteries, no the safety authorities were no informed and now that they kmow about it they are adding it to the investigation.

If a part is replaced for a known reason with no safety impact, there is no requirement to report it. If all LRU replacements went to the regulators they'd be getting hundreds or thousands of reports per day. Any LRU replacement that does have safety implications does get reported to the regulators.

Quoting BoeingVista (Reply 173): The Seattle Times article says 100 - 150 batteries failed fleet wide, I don't see how Boeing can have 100 plus Li-ion batteries plus multiple fail knowing that failed Li-ion batteries can cause fires, on a fleet of under 50 aircraft and not consider this a safety issue.

The articles says 100-150 batteries were *replaced*. This is not the same thing as failed. There is also *zero* reason to assume that replacements are safety issues, absent other data. The 737NG fleet has eaten, literally, tens of thousands of thrust reverser unlock handles in its lifetime. All 737 mechanics know this and used to keep lots of spares on hand...but it was always purely an economic/reliability issue so the regulators didn't care.

Quoting BoeingVista (Reply 179): You prevent deaths by investigating unexpected failures and if 100 failed 40kg Li-ion batteries on an aircraft doesn't ring alarm bells knowing the power that they can unleash when they go bad then you are in the wrong business.

Most of them, as the articles flat out stated, were replaced because they were inadvertently discharged in service. That's no an unexpected failure, that's what happens when you run an aircraft battery down. You *have* to replace it because there's no way to power the airplane up, hence no way to charge the battery while installed.

Quoting FlyingAY (Reply 185): Considering the nature of a LiIon battery, I think the system should automatically try to prevent a situation where the battery gets too empty and must be replaced. Charge the battery automatically as needed, raise an alarm if the capacity gets low and cut off the power before a critically low charge is reached.

It does. This is exactly what happens. As I've stated before, engineers aren't idiots. They know that if you run a lithium battery down to far you risk damaging it...so you don't let it run down that far. The BMS watches the battery condition, annunciates when it's getting to low (EICAS message) and, if it continues to run down, cuts the battery off before the voltage gets too low to be a danger. All those are features in there to *prevent* a thermal runaway. Since you need battery power to get the computers up to close the power contactors, once the battery protectively shuts itself off you can't recharge it on the airplane. You have to swap it for a charged battery. This is an intentional safety feature.

Quoting FlyingAY (Reply 185): Why would they be run down so far that a low-voltage cutout gets activated?

Because the 787 is rather power hungry relative to it's predecessors so you can't run it on battery alone on the ground for very long. It's very easy to think that you can get done with whatever you're doing fast enough to not require ground power but, if you're even a little late, you'll run the battery down to the point that the BMS protection kicks in.

Quoting FlyingAY (Reply 185): If most of the batteries had run down so far that the batteries are dead, why is there no mechanism that cuts the power before the battery is dead?

There is. There're not dead, they're "bricked" *because* the mechanism to cut off the power before the battery is dead did what it's supposed to.

Quoting FlyingAY (Reply 185): It would seem like bad design to let the battery discharge that far that it is rendered unusable.

You're running the causation chain backwards...the battery has finite capacity. If you run it down far enough that it's *going* to be rendered potentially unsafe by continued discharge, you stop discharging it. This was an explicit requirement of the FAA special condition for the battery in the first place.

Quoting seahawk (Reply 186): Although I must say it would have been interesting to know if Boeing had to report battery changes to the FAA during the test flight phase and if there have been any problems during that phase.

During F&R testing, all part replacements (regardless of reason) are reported to the FAA.

Quoting seahawk (Reply 186): All involved parties must come clean quickly now, before the reputation of the Dreamliner, FAA and Boeing is damaged.

As far as damaged reputation, it's far too late for that.

Quoting BoeingVista (Reply 193): Yes, if you see a whole bunch of unpredicted failures you need to investigate without preconceptions and find the cause which could be anywhere in the system.

They're not unpredicted failures. If you run the battery down, it's *supposed* to protect itself and shut off such that you need to replace it. That's what happens when you run a 787 down. You're also presupposing that all replacements were the same cause...when you have a known cause (battery run down) then you don't go looking for a battery problem (since the battery did what it was supposed to do), you look for the procedural problem (why did the battery get run down).

Quoting keegd76 (Reply 205): Just for clarification, what is the battery in question being used to power? I thought I read earlier that it was a back-up supply for the cockpit instruments. If true then that suggests it isn't being called on very often (i.e. drained). However if, as someone pointed out, the battery is used to power systems while the plane is inactive on the ground then it begs the question, shouldn't the plane hooked up to ground power when its on the ground?

In flight, it's the backup for the necessary avionics. On the ground, it powers the cooling fans, displays, and computers necessary to "wake up" the airplane. The intended design is that it only has to do this long enough to get the APU going (where the APU battery comes in) or to connect ground power...on the ground you don't have much time on main battery power alone. There is a low-power towing mode (basically just lights and brakes) for maintenance to move the aircraft, which is also powered by the main battery.

Quoting BoeingVista (Reply 208): The batteries run down until they get to a damaged state ie, need replacement.

No, they run down until the BMS protects them so they *don't* get damaged, and they need to be replaced with a fresh battery because the battery can no longer provide power.

Quoting ncfc99 (Reply 211): A few failures (say 10 or so) I could understand being classed as singular incidents, but 100-150 battery failures and 2 major failures, need to be investigated to see if there is a common failure of some type, be it battery design of manufacturing fault, charger or charging system fault or many other number of issues I don't have the inteligence to understand.

They are investigated and there isn't a common cause. Running a battery down until it shuts off is not the same as it catching fire when it's not over-discharged.

Quoting ncfc99 (Reply 211): I'm trying to understand why alot of singular failures of the same component(I understand not the same failures) didn't present itself as an issue.

They do present as an issue...they're just not all the same issue. In all of those replacements-because-the-battery-ran-down you're talking about the battery working *exactly as designed* and a procedural error where the batteries were getting run down. In the two fires you've got batteries that are *not* working as designed. Those are very different situations.

Quoting ncfc99 (Reply 211): When the JAL bird had its issue after over 100 other battery issues, I would hope alarm bells started ringing at that point, if they hadn't done so before.

When a component does what it's supposed to do it rings different alarm bells than when it doesn't.

Tom.

Quoting AeroWesty (Reply 223): You have to go back and read the Seattle Times article. It wasn't 100 destroyed batteries because of over-discharging. Many, many were disabled simply due to mechanics disconnecting the batteries improperly. How many times do folks have to repeat this for people to get it?

How often does a mechanic have to disconnect those batteries?

Quoting BoeingVista (Reply 162): ANA changed 10 batteries between May and December 2012

Quoting BoeingVista (Reply 162): This fills in a few more blanks that have been speculated about, yes there were widespread issues with the 787 batteries,

So does this mean that the FAA and Japan authorities are also investigating whether workers followed the proper procedures when they changed these batteries?
Regardless of the reasons for the initial change, if one does not follow the proper procedure the new battery will have a higher failure rate and heaven forbid, cause something more catastrophic to occur, is this worthy of investigation?

So far, I have not seen much commentary on which a/c had repeated battery changes and whether the same personnel effected the change. Since the batteries essentially burned themselves up, all we are left with is going to the OEM who so far has found no defects in their batteries, no QA issues, the chargers and monitors seem to be working, the safety feature of locking out the battery when it gets to a certain limit was in effect which resulted in changes being required.

Quoting UALWN (Reply 204): The article also says that "The frequency of battery failures reflects issues with the design of the electrical system around the battery, said the person on the 787 program."

I hope it does not also mean that like some of us when we get a new battery, we choose to leave the a/c on when we shut down our car thus generating a hugh pull on the battery when the vehicle is started.

Hopefully one segment of the team has started looking at how the batteries are used on the ground, the systems for use in the air have been through more testing than whatever procedures an airline will put in place for its ground handling,
since its an electric plane the batteries should be running all the time.

Quoting seahawk (Reply 227): How often does a mechanic have to disconnect those batteries?

Not a clue.

http://seattletimes.com/html/busines...020241385_787deadbatteriesxml.html

The article only seems to mention one ANA battery failure out of 10 replaced batteries.

As for the two batteries that are being investigated, we don't know if those batteries failed, or if there was some external cause.

The article also seems to contradict itself. It says there is a safety cutoff at 15% of charge.

It then implies that the cutoff doesn't actually work if you do something like open a refueling door.

If opening a refueling door bypasses the battery safety cutoff, it would seem to be a poor design.

I'm guessing that there is a battery safety cutoff, and that the article is wrong about it being bypassed so simply.

Quoting par13del (Reply 228): I hope it does not also mean that like some of us when we get a new battery, we choose to leave the a/c on when we shut down our car thus generating a hugh pull on the battery when the vehicle is started.

Your a/c compressor is not running when you start your car, unless your car is very old.

Doesn't matter if you leave the a/c turned on, the compressor is not turned on until after the engine is running.

There is a clutch on the compressor which is not engaged when the engine starts, so it spins freely until the engine is running.

[Edited 2013-01-30 06:27:17]

Quoting AeroWesty (Reply 214): Okay, I read that link. It's incomplete. You have to read the Seattle Times article in reply #169 and read the next few replies to get the full gist of the battery replacement issue.

from that link

"However, she acknowledged that there has been a series of problems and listed %u201Cthe top three reasons for Boeing returning batteries%u201D as batteries running down, being improperly disconnected, or exceeding their expiration date."

That could mean anything from 90% of the issues is battery running down, and the others single digits to almost equal thirds which would still put "being improperly disconnected" as less than the majority of reasons which would seem to suggest "mishandling" is still not the main reason for the battery exchanges.


And if they are running down "inadvertently" from things like fueling up causing drain charge as gauges light up, as cited in the article and then locking out, the electrical system should be designed to cut off the power before the battery drops that low, even my cheap subaru cuts off its lights after x minutes if you leave doors, dome lights, headlights on! Maybe Boeing needs Fuji Heavy to do the electrical system besides the wing box. Seems they have a simple automotive system to fix some of the issues on their shelf already and I'm sure they would love to see the 787 flying again and no interruptions in their Nagoya operations!

As a non engineer all this sounds like the battery itself may not be the issue but the charging system needs something to stop parasitic drain and stop excessive undercharging and some new procedural changes- eg no fueling while plane is dark!.

Quoting ncfc99 (Reply 225): Battries replaced due to being expired is expected. I asked further up the thread, how long are the expected to last before removal and overhaul?

DIdn't I see the number 2000 hours somewhere up the thread? So many posts...

Quoting BoeingVista (Reply 224): What number of batteries do you think 'failed' give me a number or are you of the opinion that until a statement comes down from a mountain in Chicago written on stone tablets that nothing is to be believed so none failed?

Actually, the three items I mentioned - discharged to safety interlock levels, expired, and faulty - were directly quoted from a Boeing employee.

As far as "yawn, I'm much better informed than you are" jeez, what are we going to compare next?

Quoting tdscanuck (Reply 226): Quoting ncfc99 (Reply 211):A few failures (say 10 or so) I could understand being classed as singular incidents, but 100-150 battery failures and 2 major failures, need to be investigated to see if there is a common failure of some type, be it battery design of manufacturing fault, charger or charging system fault or many other number of issues I don't have the inteligence to understand. They are investigated and there isn't a common cause.

Maybe I'm over complicating or over analyzing things. Either way, I know i'm getting a headache try to get my head around it.

Quoting tdscanuck (Reply 226): Running a battery down until it shuts off is not the same as it catching fire when it's not over-discharged.

That much is obvious.

Quoting tdscanuck (Reply 226): They do present as an issue...they're just not all the same issue. In all of those replacements-because-the-battery-ran-down you're talking about the battery working *exactly as designed* and a procedural error where the batteries were getting run down.

I mentioned further up the thread about procedural issues possibly causing the undercharged batteries. I also mention that if it carries on at quite a frequent rate as it seems to be at the moment, it would need to be addressed and engineered out. The same component have many issues would indicate a weak point to be addressed IMHO.

Quoting tdscanuck (Reply 226): Most of them, as the articles flat out stated, were replaced because they were inadvertently discharged in service. That's no an unexpected failure, that's what happens when you run an aircraft battery down. You *have* to replace it because there's no way to power the airplane up, hence no way to charge the battery while installed.

This isn't what the article says, it say that "Most of the batteries were returned because they had run down so far that a low-voltage cutout was activated." it does not directly state why they ran down, so the question of why the batteries ran down is open.

Quoting tdscanuck (Reply 226): Most of them, as the articles flat out stated, were replaced because they were inadvertently discharged in service. That's no an unexpected failure, that's what happens when you run an aircraft battery down. You *have* to replace it because there's no way to power the airplane up, hence no way to charge the battery while installed.

Again, no the article does not say that. Also a "sensible' design would maybe stop the drain before the batteries became unusable? Plus you say I assign all of the battery changes to failure, you seem to assign all the changes to inadverant discharge, what about the others or are you maintaining that there were no unexpected failures? ANA says that they had battery failures.

Quoting tdscanuck (Reply 226): No, they run down until the BMS protects them so they *don't* get damaged, and they need to be replaced with a fresh battery because the battery can no longer provide power.

Semantics but I'll give you that bricked may not be "damaged" as in dangerous though as the batteries are rendered unusable through some sort of cut out I don't think that "damaged" as in beyond repair is an unreasonable description.

It would be informative to know the margin between bricked and damaged though.

Quoting rheinwaldner (Reply 219): So as a summary: 100 destroyed batteries because of over-discharging indicate a poor charger design and a wrongly dimensioned battery.

Replaced != destroyed. According to the articles, most were pulled for expiration (not destroyed) or the low-voltage interlock cutting in to *prevent* them being over-discharged and destroyed (also not destroyed).

Quoting BoeingVista (Reply 224): You really make me LOL; you contend that bricked batteries are not failed? or faulty batteries are not failed?

"Bricked" is probably not the right term, although I used it too. If you discharge the battery to low, the battery shuts down to protect itself. You can't recharge it on the aircraft because it's shut down. You swap it with a good battery so the airplane can get going and then recharge it on a bench somewhere...it's not really "bricked" in the sense that it doesn't work any more, it's "bricked" in the sense that you need to swap it out and recharge it off-aircraft. This isn't a battery failure by any normal definition, it's how the battery is supposed to work.

Quoting ncfc99 (Reply 225): What is making the batteries fail or have to be replaced is the big question, IMHO.

Failure is an open question. Replacement appears to have obvious and known causes, according to all the articles...the batteries either expired (reached their time interval for replacement) or were inadvertently run down to the point that the low-voltage cutoffs activated.

Quoting ncfc99 (Reply 225): --If they are being discharged to the level that they 'brick' themselves, I have to ask why they are getting that discharged so regularly (ANA stated 5 out of 10 had shown 'unexpectedley low charge'. I would have thought 'bricking' due to low charge should be a rare event.

Any time you need to power up the airplane without APU or ground power, the battery is the one doing it. It doesn't take long to run it down, especially if you do something like leave the fuel door open (in which case the battery is powering the fuel indicating system). An important note about the 787 is that the main computer hosts almost all the major functions except flight controls, so the power draw is kind of binary...if you want to do anything, even something as simple as refuel, you need to power up at least one of the common computing resource (CCR) cabinets, since they host the fuel indicating system and fuel valve control. That means you power up the whole computer, it's associated cooling fans, the indicating system probes, and the power distribution units that power the probes and valves.

Quoting ncfc99 (Reply 225): --Some faulty batteries on a fleet of 50 aircraft in commercial use (100 batteries) I would expect the number of failures to be quite low at this point. Its not new tech as such, its new in an aircraft. Reliability of the batteries should be good, should it not?

The normal failure curve is a bathtub...you have low reliability early (infant mortality), a long period of pretty constant failure rate (normal operation), then low reliability again (age). This is at a component, not aircraft, level.

Quoting trex8 (Reply 232): And if they are running down "inadvertently" from things like fueling up causing drain charge as gauges light up, as cited in the article and then locking out, the electrical system should be designed to cut off the power before the battery drops that low

The electrical system *is* designed to cut off the power before the battery drops that low. That's why they have to replace the battery if they run it down .I feel like this is going in circles...people demand that the system cut off the battery to prevent over-discharge, then complain when the over-discharge protection does its job and results in the battery being replaced.

Tom.

Quoting AeroWesty (Reply 212): Okay, real simple terms. Line up 100 blenders on your kitchen table. I take a sledgehammer to 95 of them

* I'm not qualified. Got that out of the way.

The thing about the battery failures that I think might be relevant is that it exposes an issue, operator or design error, that may stress the safety systems and expose problems. It's not a sledgehammer to a blender, it's more like using a blender for a purpose it was not designed.

So there is protection placed on these batteries for certain conditions, and many of the batteries bricked because those conditions were met. What about batteries that came close but did not exceed those conditions? What about batteries that came really really close?

Related? Sure, somewhat related, and certainly worth looking into. Did any of the batteries that caught fire experience a near, uh, disabling event? Is there any logs of this? How rigorous was the testing of these failsafe mechanisms?

No conclusions, I just think it's a valid concern. See *

Quoting tdscanuck (Reply 226): In flight, it's the backup for the necessary avionics. On the ground, it powers the cooling fans, displays, and computers necessary to "wake up" the airplane. The intended design is that it only has to do this long enough to get the APU going (where the APU battery comes in) or to connect ground power...on the ground you don't have much time on main battery power alone. There is a low-power towing mode (basically just lights and brakes) for maintenance to move the aircraft, which is also powered by the main battery.

   Thanks for the info.

Quoting markalot (Reply 238): Did any of the batteries that caught fire experience a near, uh, disabling event? Is there any logs of this? How rigorous was the testing of these failsafe mechanisms?

Do Yuasa also supply the charging system for the battery? If so then I'd assume they would have tested the failsafe mechanism fairly rigorously. Having said that, what would happen if you tried to charge a 'bricked' battery? I'd imagine the design would prevent that but again I don't know.

Quoting tdscanuck (Reply 237): Quoting ncfc99 (Reply 225):--If they are being discharged to the level that they 'brick' themselves, I have to ask why they are getting that discharged so regularly (ANA stated 5 out of 10 had shown 'unexpectedley low charge'. I would have thought 'bricking' due to low charge should be a rare event. Any time you need to power up the airplane without APU or ground power, the battery is the one doing it. It doesn't take long to run it down, especially if you do something like leave the fuel door open (in which case the battery is powering the fuel indicating system). An important note about the 787 is that the main computer hosts almost all the major functions except flight controls, so the power draw is kind of binary...if you want to do anything, even something as simple as refuel, you need to power up at least one of the common computing resource (CCR) cabinets, since they host the fuel indicating system and fuel valve control. That means you power up the whole computer, it's associated cooling fans, the indicating system probes, and the power distribution units that power the probes and valves.

Quoting tdscanuck (Reply 237): Quoting trex8 (Reply 232):And if they are running down "inadvertently" from things like fueling up causing drain charge as gauges light up, as cited in the article and then locking out, the electrical system should be designed to cut off the power before the battery drops that low The electrical system *is* designed to cut off the power before the battery drops that low. That's why they have to replace the battery if they run it down .I feel like this is going in circles...people demand that the system cut off the battery to prevent over-discharge, then complain when the over-discharge protection does its job and results in the battery being replaced.

I fear I maybe one of tose 'people' that you are refering to. From what I can gather from your posts, I have assumed the batteries would have more capacity than they do before they would 'brick' themselves to eliminate the chore of replacement. Sorry if I'm making you go in circles.

Thanks for your patient replies to my posts in this thread and many informative posts in the other threads. I'm an intrested novice and I'm on this site to learn, and I'm grateful for the posts from yourself and the likes of CM, Ferpe, Lightsabre, Astuteman and many others.

[Edited 2013-01-30 08:34:31]

Quoting cornutt (Reply 233): DIdn't I see the number 2000 hours somewhere up the thread?

Thanks. That should give us a vague idea of how many got replace due to being expired.

Quoting cornutt (Reply 233): So many posts...

That there is......

Quoting BoeingVista (Reply 236): Also a "sensible' design would maybe stop the drain before the batteries became unusable?

That leads to circular logic, though... If you have a system that stops drawing current from the battery before it bricks, well, now you can't draw current from the battery. So it's almsot the same as being bricked, the difference being that you can recharge it once you have another source of power. However, until you get that other source, there's no difference.

Quoting BoeingVista (Reply 236): Semantics but I'll give you that bricked may not be "damaged" as in dangerous though as the batteries are rendered unusable through some sort of cut out I don't think that "damaged" as in beyond repair is an unreasonable description

If I understood what I read up-thread, a battery that bricks itself can be restored to service by the manufacturer. So it's still useable; it just needs service. Kind of like an engine that has reached its TBO time.

All batteries are limited-life items. We could quibble that the limited life isn't long enough, but that's a service issue, not a safety issue. The safety issue here is the two batteries that caught fire.

Quoting tdscanuck (Reply 237): ..if you want to do anything, even something as simple as refuel, you need to power up at least one of the common computing resource (CCR) cabinets, since they host the fuel indicating system and fuel valve control. That means you power up the whole computer, it's associated cooling fans, the indicating system probes, and the power distribution units that power the probes and valves.

You sure about this? All the control / indication is on the re-fuel panel. I could see the fuel quantity system, and a few valves and lights.

Quoting BoeingVista (Reply 236): This isn't what the article says, it say that "Most of the batteries were returned because they had run down so far that a low-voltage cutout was activated." it does not directly state why they ran down, so the question of why the batteries ran down is open.

At least the ANA article states that they all happened on the ground out of operation,. that is why there were not "FAA" reportable (the Feds don't care how many batteries you run down on a parked/non operational airplane). They also stated that there were no delays or cancellations, therefore the issues must have been discovered well before any scheduled departure (like when they tried to power the airplane).

[Edited 2013-01-30 09:07:20]

Quoting BoeingVista (Reply 236): though as the batteries are rendered unusable through some sort of cut out I don't think that "damaged" as in beyond repair is an unreasonable description.

They're rendered unusable aboard the airplane using the airplane's charging system. However, they can be reconditioned off the airplane and returned to usable service.

As to why this must be done off the airplane, I expect it's a safety measure. It has been noted that once a Li-Ion battery has been deeply discharged, it is more susceptible to thermal runway when re-charged. A shop offers a more isolated environment should the battery enter thermal runaway and catch fire and you can more easily apply extinguishing agents to said fire in a lab than in the EE bays.

Quoting ncfc99 (Reply 240): I have assumed the batteries would have more capacity than they do before they would 'brick' themselves to eliminate the chore of replacement.

As I understand it, the primary reason the batteries can provide "ground power" to the plane is because operators wanted the ability in areas where they do not have the proper ground power facilities. I expect Boeing has published time limits for powering various functions off the battery based on the draw of those functions. As such, it sounds like that in at least some cases, the aircraft support crew are not properly "minding the clock" and are exceeding these limits, with the result that the battery hits the threshold and the protection circuitry kicks in.

Quoting BoeingVista (Reply 236): Also a "sensible' design would maybe stop the drain before the batteries became unusable?

That's exactly what the design does. How is that not clear? The operator does something that drains the battery, if he/she keeps doing it long enough to drain to the low charge limit, the battery shuts itself off to prevent damage. That sounds pretty sensible to me. The battery is now "unusable" only in the sense that there's nothing left on-aircraft that you can charge it with -- you would need the electrical system live in order to charge the battery from ground power, and without the battery (and no engines/apu running, on the ground) there's no way to run the electrical system. This is just elementary stuff.

What you keep insisting, without any proof or reasonable basis as far as I can tell, is that these drained, shut-off batteries are permanently damaged. I don't think that is the case, from what Tom is saying, and there's nothing in the article that I could see that makes the connection low-limit-shutdown --> permanently damaged and unusable battery.

By the way, if you're saying that the battery should shut down the aircraft while there's still enough charge left to boot the system for ground power recharge -- I'm willing to bet that the design assumption was that ground handling would abide by airline SOP and the SOP would say "Don't do that" to any procedure that's going to run the battery dry. You certainly don't want to (say) unilaterally power down during refueling, disabling quantity indicators, if there's any power left, I would think that that's a recipe for worse problems than a dead battery. Now, if the design is such that the handler has no indication of battery level except for the airplane going dead, that's a different issue. But I've read nothing stating that, and you certainly can't draw that conclusion from any published matter I've seen.

Based on the large amount of battery problems I'm guessing Boeing already had engineers and the vendors working on that issue -- is this where the "mysterious" software change comes in?

Also, during flight test (except for specific conditions) and production the airplanes are almost always connected to external power on the ground (sometimes 24/7) so there is very little use if any of the APU or MAIN battery. This may be why the issues in service may not have been seen during Boeing operations and only when the customers began using the batteries to power the various systems more often (APU start, towing, fueling etc).

Quoting max550 (Reply 218): It sounds to me like a battery redesign would be a better solution than switching to an entirely different type of battery or power source.

My guess as a project manager - because that's the only way I know to approach this - is that in the absence of a "smoking gun", you're going to see strengthened containment, additional software and/or hardware safeguards in the charging system, and a redesigned lithium ion battery. It's not going to be one thing; it's going to be all of them. Boeing is probably in fact working on this right now, because there's no point waiting. No system is perfect even if it is working as intended; this is a chance for Boeing to further improve the entire battery and charging system. If the investigation drags on, Boeing can go to the FAA and say "look, we've redesigned all this stuff, we can demonstrate its safety" and maybe that will be enough to get the grounding lifted.

A lot of new technologies don't have one single flaw that you can find and fix; you just make iterative improvements until you're at the point where you need to be. That may be the case here. It should have happened before the plane was certified, but it didn't, so this is another chance to further refine the system.

Quoting par13del (Reply 228): So does this mean that the FAA and Japan authorities are also investigating whether workers followed the proper procedures when they changed these batteries?

The FAA isn't investigating anything, anywhere. The NTSB is investigating the JAL incident because that happened here. The JTSB is investigating the ANA incident because that happened in Japan. They're sharing data back and forth. No doubt the JTSB is investigating whether proper procedures were followed; that's a standard component to any investigation.

Quoting PITingres (Reply 245): Quoting BoeingVista (Reply 236): Also a "sensible' design would maybe stop the drain before the batteries became unusable? That's exactly what the design does.

Well, it may be what the design is supposed to do. It doesn't seem to be what it actually does. The battery in the ANA incident reportedly dropped to near zero voltage before it went belly up. "Unexpected drops" in voltage seems to be one of the big problems here.

I don't really believe that re-fueling or towing is the main cause for battery replacements. I can't think of too many occasions when an airplane would be re-fueled without the airplane being powered. Towing, the brakes should really only be used once it is over, to set the parking break.

With that said, I wonder how many fuel door switches have been replaced and or adjusted? How often does an airplane lose external power and the battery switch remains on? There are simply so many different reasons why a battery can get drained on the ground.

I think the NTSB will look at the shop paperwork for the removed batteries to see if they can see at least one that might have had a cell issue that could have caused a thermal runaway. If they can find that cell, they might be able to test for a root cause.

Cheers

[Edited 2013-01-30 09:40:16]

Quoting spacecadet (Reply 247): Well, it may be what the design is supposed to do. It doesn't seem to be what it actually does. The battery in the ANA incident reportedly dropped to near zero voltage before it went belly up. "Unexpected drops" in voltage seems to be one of the big problems here.

I'm not seeing the connection. Not saying that there isn't, but I don't see how you can logically conclude that battery self-shutoff due to low charge under load (with no charging source) is correlated with battery undervolt from a supposedly charged battery under no load. The former is a normal (if perhaps procedurally inadvisable) usage, the latter is unexpected and would seem to be internally induced. As far as I know there's no reason to think that there was any significant drain on the ANA main battery in flight, it should not have been anywhere near a loaded low-charge shutdown.

Again, there might be something there and if I were the NTSB I'd certainly review the situation, especially since they apparently haven't found anything else yet. Sometimes treasure-hunting is the only way to the answer. I just object to the leaps of illogic being taken by some (other) posters in this thread; some of the inferences being made are just incorrect.

Quoting spacecadet (Reply 247): A lot of new technologies don't have one single flaw that you can find and fix; you just make iterative improvements until you're at the point where you need to be.

I agree 100%.