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787 Batteries and Chargers - Part 1

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787 Batteries and Chargers - Part 1

Old 7th Feb 2013, 15:35
  #541 (permalink)  
 
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An organic corollary.....

Imagine the human brain suffering random amyloid deposition (sclera) that block neural pathways, and cause the brain to lose efficiency...

Yuasa's batteries have rapid onset Alzheimers....

Leave them alone, save them for emergency supply needs only.

Unless the charge range and heat cycle can be rigidly, completely controlled...

Fragile, these little boxes....

Last edited by Lyman; 7th Feb 2013 at 15:38.
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Old 7th Feb 2013, 17:19
  #542 (permalink)  
 
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Interesting update mentioned in r&n:

Boeing Plans Battery Redesign to Get Dreamliners Airbone Again | Frequent Business Traveler

A couple of weeks or so ago, I was trying to determine if each cell
had it's own associated temperature sensor, rather than one to cover
the whole enclosure. The following from the above article suggests that
there may *not* be one per cell:

"Boeing may <snipped> possibly add better heat sensors".


I seem to be the only one out of step here, as everyone else
still seems to be obsessed with the battery and it's construction,
but there are other possibilities to consider.

Still think that the battery would only fail in such a way if it
were abused, which suggests either operation outside cell voltage
limits, or inadequate cell temperature sensing, during fast charge
or high current load.

Might need just a software mod to fix, though after all the hysteria
only an ejectable, fully armoured enclosure would
be good enough for some ...
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Old 7th Feb 2013, 17:44
  #543 (permalink)  
 
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I just went out and had a 6 mm thick SS enclosure fabricated for my Galaxy S2 so I don't self immolate with it in my pocket. I also put a 100mm spacer between the battery and the phone so it doesn't short out. I have 3 temperature and pressure sensors installed, hooked up with Bluetooth to my headset, to warn me about impending doom. All of this so I can hook up my cheap 2 dollar knock off charger to my 7 dollar knock off Chinese battery. I believe everybody should have this setup and am going to demand all government safety bodies implement these measures immediately.

Does this sound silly? Of course it does.

This is extremely mature technology, that has a minor flaw that will be fixed.

All the short circuits were effects, not causal. You can put all the space between cells you desire. You can put 100 meters between each cell, but the cells will still short circuit internally if they heat and swell up. This is thermal runaway.

Extra sensors, in an aircraft? Maybe. I would vote yes.
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Old 7th Feb 2013, 18:04
  #544 (permalink)  
 
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From Boeing Land...
The National Transportation Safety Board (NTSB) has pinpointed the start of the 787 Dreamliner battery fire on a parked Japan Airlines jet a month ago today as a short circuit inside a single cell.

The agency still hasn’t identified the cause of the initial short circuit but has narrowed down the suspects.

Details provided by the NTSB make clear that Boeing will have to redesign the battery for a long-term fix.

In addition, the NTSB pointed to failures in the airplane certification process conducted by Boeing and the Federal Aviation Administration (FAA), which failed to identify the hazards revealed by this incident.

“The assumptions used to certify the battery must be reconsidered,” said NTSB chief Deborah Hersman in a detailed press briefing. “Our task now is to see if appropriate layers of defense and checks were built into the design, certification and manufacturing process.”

NTSB questions Boeing&rsquo;s 787 battery design and certification after short circuit | Business & Technology | The Seattle Times
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Old 7th Feb 2013, 18:19
  #545 (permalink)  
 
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USMCProbe:
I just went out and had a 6 mm thick SS enclosure fabricated for my
Galaxy S2 so I don't self immolate with it in my pocket. I also put
a 100mm spacer between the battery and the phone so it doesn't short
out. I have 3 temperature and pressure sensors installed, hooked up
with Bluetooth to my headset, to warn me about impending doom.

All of this so I can hook up my cheap 2 dollar knock off charger to
my 7 dollar knock off Chinese battery. I believe everybody should have
this setup and am going to demand all government safety bodies implement
these measures immediately.
So long as you realise that the phone would no longer function as a
phone, due to the sceening ?, but hey, it's still got the rest of it's
functionality, games, camera at both sides etc etc. Seriously though,
such irony may be lost on many, who would have this drag on for as
long as possible.

This is extremely mature technology, that has a minor flaw that will
be fixed.
Of course it is, but there are deficiencies in this particular design,
otherwise the batteries would not have ended up in the state that they did.


Extra sensors, in an aircraft? Maybe. I would vote yes.
Most likely, though I suspect that improved battery management will
be the key to solving the problem. Can I say that again ?. At least
it appears as though they are (finally) looking seriously at that
area (charger, BMS) now...

Last edited by syseng68k; 7th Feb 2013 at 18:31.
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Old 7th Feb 2013, 18:30
  #546 (permalink)  
 
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USMC

All the short circuits were effects, not causal. You can put all the space between cells you desire. You can put 100 meters between each cell, but the cells will still short circuit internally if they heat and swell up. This is thermal runaway.
Technically, I agree. Cause? Shutdown syndrome. Each Separator fault at the "Capillary" level occludes a penetration, preventing Lithium ions from transiting the separator. This creates heat, and a degradation of battery CAPACITY, which "ages" the cell. The range of permitted charge level narrows, the battery degrades. Eventually the cell produces a thermal runaway, and we see JAL, ANA.

The best way to remedy the problem is to wind the cell radially, not "folded".

The prismatic shape and the folds produced, cannot dissipate heat quickly enough, or efficiently enough, to ennable a long life and efficient profile for the "Eight battery group" as built by YUASA.

It's the BATTERY....

And BOEING'S immature pride, and stubbornness in trying to push a bad position.

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Old 7th Feb 2013, 18:52
  #547 (permalink)  
 
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Lyman:

The prismatic shape and the folds produced, cannot dissipate heat quickly
enough, or efficiently enough, to enable a long life and efficient profile
for the "Eight battery group" as built by YUASA.
So, what about all the other applications for these cells, for which we
have no news of any problems ?. As I said in an earlier post, they
have been approved for use by NASA, the ESA and others only after very
extensive testing, so are they all wrong ?.

The whole idea is for the cells not to overheat in the first place, for whatever
reason and that's down to good design for the bms..

Battery topology really doesn't matter, so long as they are operated
within data sheet limits. All li chargers utilise temperature sensing and
should backoff charge current to avoid overtemperature. Sensing is
critical, hence the earlier disussion about individual cell temperature
sensing, as opposed to overall enclosure sensing.

Laptop batteries may get away with a single sensor, but it's just not
enough for an enclosure of that area. If there's adequate sensing, the
cells won't overheat to start with.

Of course, this doesn't cover the high rate of discharge case, such as
apu starting, but once again, the battery can be safely disconnected from the
load if excessive temperatures are seen by the bms...
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Old 7th Feb 2013, 19:09
  #548 (permalink)  
 
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Chris.

with great respect, you are absolutely right. So too, am I. In your recent post your questions all have answers. My interpretations of the problems and the solution are based on prior art, prior knowledge, and I create an interpretation.

Architecture, partially, Control/management, parenthetically. Application, absolutely.

In post #525 I quoted what I perceive to be the basic and fundamental problem.

For YUASA. BOEING did not feverishly replace the BATTERIES because they thought the chargers and controls needed replacement.

OCCAM.

One more time. BOEING knew. All along. There is no mystery.

The current charade is a produced drama.

Too bad BOEING is too sick to admit the problem, fix it, and start flying.

PRIDE can be way expensive.
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Old 7th Feb 2013, 19:20
  #549 (permalink)  
 
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Chris. I think the separator will be upgraded, thickened, and a better method of perforating the film will be found. Also, I believe quality of paste, and applicating method will be upgraded. Of course I think cylindrical shape will be utilized, if it can be demonstrated that it will peform in a Battery of this capacity and size.

I wanted to say ceramcs will play a part, but I think that is a way off, plus the possibility that in an explosion, ceramics will fracture and become shrapnel.

Hersman claims the method of certifying the technology will be examined.

YA THINK?
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Old 7th Feb 2013, 21:16
  #550 (permalink)  
 
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Lyman:

Chris. I think the separator will be upgraded, thickened, and a better
method of perforating the film will be found. Also, I believe quality of
paste, and applicating method will be upgraded. Of course I think cylindrical
shape will be utilized, if it can be demonstrated that it will peform in a
Battery of this capacity and size.
Sorry, but that's just guesswork without any of the required science. Perhaps
ok in r&n, but tech log ?. Just because one man who has experience of the
technology for a different application says it's wrong doesn't mean that
this design is wrong. If the cells are managed properly, then there should
never be a problem. If the cell management fails, then anything might happen,
so perhaps the enclosure and cell mounting should be revised to better
account for worst case conditions. I'm not qualified to comment on that
though.

I wanted to say ceramcs will play a part, but I think that is a way off,
plus the possibility that in an explosion, ceramics will fracture and
become shrapnel.
Kevlar or carbon fibre ?. Perhaps they use that for intercell spacing
already ?. Internally, such cells can use an interplate material that's designed to
be self healing.

Hersman claims the method of certifying the technology will be examined.
New technology and new application of a sensitive technology may need a
different set of design rules to standardise usage for aviation.

For those who are not engineering bods, will try and get an image together
that describes the overall charger - bms - battery system. While the battery
enclosure layout might have been better, you can't consider such a failure
by looking at any single item in the system. You have to look at the whole
system and understand how each part interacts with another.

While we only have limited information, it should be possible to work out
how all the bits fit together, their interactions and possible failure
modes...
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Old 7th Feb 2013, 21:39
  #551 (permalink)  
 
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Any method of winding will disguise almost all the surface area of the separator.
Since each failure begins at a perforation in material that is twenty five microns thick, the capability to monitor all the area is impossible, and sampling the entire cell is not sufficient.

I am sorry, it is not guesswork. It is based on knowledge I have researched, and based my intrpretive skills upon.

Kevlar and Carbon fiber (sic), are not stable in these temperatures, and off gas.

Ceramics is a natural, even as a suitable separator, in and of itself. Porous, heat resistant, and non conductive.

As to certification, the FAA relied almost entirely on the applicant, BOEING, to write its own rules.

I am grateful for the opportunity to have this discussion, Chris.
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Old 7th Feb 2013, 21:49
  #552 (permalink)  
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For a better understanding (and hopefully avoid endless conjecture) of the prior art vs the new art of packet cell construction, here's a glimpse into patent 7629077 awarded to some smart lads at Qinetiq Ltd:



Prior




ABSTRACT
An electrode assembly is formed by respectively overlaying a sheet cathode 1, a sheet separator 3 and a double-sided sheet anode 8 to form a stacked structure 10, and subjecting the stacked structure to multiple folds, wherein the initial fold comprises folding the cathode in half around the double-sided anode so as to surround the respective upper and lower active anode surfaces thereof. The multiple folds may comprise one or more subsequent parallel folds made with the fold line D-D extending perpendicular to the original length of the stacked structure such that its overall length is halved at each fold. A pouch battery comprising said electrode assembly has improved safety and performance characteristics. The pouch battery construction has especial application to lithium primary batteries.
New








Last edited by Machaca; 7th Feb 2013 at 21:55.
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Old 7th Feb 2013, 21:56
  #553 (permalink)  
 
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Fold at separator 3 is the mechanical and heat management weak link, imo. And line "D" where the stack "returns" on itself. (10).

Thank you Machaca.

Edit.....The "POUCH" concept is N/A on GSYUASA, as the container is likely ("rigid") polypropylene. Note in the CT scan of the failure, the more deformed batteries tend to mimic what should be, imho, the correct "shape", a cylinder.

The weaker "sides" deflect the most, the "corners" very little, and the "ends" very little, as expected.

Last edited by Lyman; 7th Feb 2013 at 22:03.
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Old 7th Feb 2013, 22:09
  #554 (permalink)  
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Ly[ing]man:

it is not guesswork. It is based on knowledge I have researched
Kevlar and Carbon fiber (sic), are not stable in these temperatures, and off gas

Absolutely beyond belief. Aramid and CF don't burn!

You seem hell bent on emulating your namesake, Lyman Gilmore.
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Old 7th Feb 2013, 22:13
  #555 (permalink)  
 
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I did not say they burned.

I cannot imagine why you are so incensed at my presence. If you ask, i will leave.
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Old 8th Feb 2013, 01:28
  #556 (permalink)  
 
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APU operation when (if) itīs battery fails

Hi,

1) From NTSB briefiing: APU stops if itīs battery fails.

I donīt understand why APU stops if itīs yet running (and generating power)

I watched the video and would like a confirmation. (not so sure)

2) Any mention on cell # 6 voltage when shorts initiated BOS event?

This info was lost? (shorts could resulted from improper cell voltage)



PS

One month after BOS event i would expect more info.
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Old 8th Feb 2013, 06:22
  #557 (permalink)  
 
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Charred to a crisp: New pictures show how full extent of damage to burnt Dreamliner batteries which prompted emergency landing | Mail Online

I found this just now. If the link works, and you scroll down, you will see a CT scan of the ANA battery, which shows different damage, at least to my eyes, than the JAL battery.

There is a CT scan of the battery. It clearly shows a damage gradient, starting at one end, and the other in is far less damaged.

To me this makes the investigation even more difficult. On the JAL battery, I did not see a single pattern of damage. i saw at least 6 cells, all being damaged in their own separate events, and finally one shorted and entered thermal runaway causing the fire.

The ANA damage shows heat damage radiating from one end of the box to the other. The last two cells at the end show little damage.

The investigators and Boeing really have their work cut out of themselves. To me it looks like two different failures.
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Old 8th Feb 2013, 06:44
  #558 (permalink)  
 
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My opinion.

ANA battery:

One battery entered thermal runaway, causing heat damage to the others.
causes:

A single defective/mishandled/damaged cell.
Bad battery charger/BMS


JAL battery:

Most of the battery was overcharged. One cell finally let go and shorted. Firemen put out the fire before too much heat damage to adjacent cells.
causes:

Bad battery charger/BMS
Aircraft electrical system noise/interferance/bonding caused overcharging.

The only common denominator is the battery charger/BMS. The two batteries, to me, look like they had two completely separate failure modes.
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Old 8th Feb 2013, 07:35
  #559 (permalink)  
 
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Lyman,
While playing armchair engineer is great fun, I am sure Yuasa has a lot of very bright boys and girls who do this for a living and have a level of experience and expertise in the subject you and I can never aspire to. I am quite confident that the cell design and testing is top notch - dare I say on this forum, from my personal experience even if in another area, more so than they would be from any US manufacturer - and that the cells will not cook off if operated within their specified envelope.

Likewise, designing electronic circuits to meet certain current and voltage targets is almost a trivial matter these days and I would not look for any design problems in either the balancing units or the charger - with a caveat on the charger in that it apparently implements a novel charging algorithm. I'm confident that the electronics faithfully applies that algorithm, but how good is the algorithm? "Novel" does not exactly square with "well known".

What it boils down to then is the system integration aspects. Despite the complexity of the individual items, it really is no different from ensuring that a bolt or rivet isn't stressed beyond its specified limits - either that or specify a better rivet. The key factor here is whether the aircraft system as a whole - the one great unknown before the aircraft started flying, since it too is "novel" - is respecting the specifications provided to the manufacturers of the various components.

Of course the investigative bodies have to take things step by step and rule out the more obvious culprits first. My reading of the reports to date is that this has been more or less done with the batteries and electronics. Leaving....?
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Old 8th Feb 2013, 11:48
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Fizz57

I could not agree more about Yuasa and would add the same comment about ANA and JAL as operators. I have friends that used to work for both. There may be some other airlines in the world that might equal their fanatical attention to detail concerning maintenance. Maybe. There are none better. This fact also reduces a lot of the uncertainty of how maintenance procedures were followed. i would expect they were followed nearly perfectly, and to the letter.
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