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  #301  
Old 03-05-2013, 03:03 PM
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If the batteries are backup and not used in flight that is a little reassuring. Would hate to be out over the Pacific with a thermal runaway battery.

But one must question if Boeing made such amatuer mistakes with the Battery cell spacing, what else have they put in this plane that is not well understood.

We know that the MBA driven design and production methodology of having subs do most things did not work out as planned for manufacturing efficiency, I wonder if the same is true for design flaws.
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  #302  
Old 03-05-2013, 03:53 PM
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Originally Posted by boxerman View Post
If the batteries are backup and not used in flight that is a little reassuring. Would hate to be out over the Pacific with a thermal runaway battery.
The batteries are likely being charged, or maintained, while in flight so you may not be as reassured as you would like to be.
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  #303  
Old 03-05-2013, 05:03 PM
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Originally Posted by docmirror View Post
BSOD <> comm aviation.

lol, I keel myself.

I'm an EE but battery tech and charging circuits are not my forte. Having said that, there is a tipping point on internal resistance of a battery where it will simply convert additional charging current into heat, and not the chemical reaction needed to recharge the battery.

This is a design consideration for Li+ type batteries, as I recall they have a typically higher internal resistance than other common Pb or Ni substrates. Again, not an expert in batts. Also, the carbon metal plates are brittle, and if they crack and/or touch, that's gonna set off a serious current crowbar situation. The charging circuit needs to be very tightly controlled with Li+.

I"m not even sure of the failure mode, but this looks a lot like current induced thermal runaway. Whether it was caused by the charging circuit, it was caused by an internal change in resistance, leading to an over-current situation I think might be the crux of the biscuit in remediation.

Things I might do as an EE to remedy:

1. multi point thermal sensing on the batt case, and maybe even in the embedded media of the batts with a closed loop control over charging current and voltage.

2. Phase controlled FET current/voltage regulation that can respond instantly to differing voltage and temp situations.

3. Increased cooling path for batteries. There's no replacement for heat extraction once the heat is being generated. You can make all the plate distances, and phenolic diffusers you want inside the batts, but when the temps start to climb, those BTUs gotta go somewhere.

Again NOT a battery expert!

You've got me fooled... ha
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  #304  
Old 03-05-2013, 08:00 PM
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Originally Posted by jcurry View Post
The batteries are likely being charged, or maintained, while in flight so you may not be as reassured as you would like to be.
More than likely.
The only time the charge can be replenished is when the engines are spooled up, therefore the possibility of a malfunction (or over-charge) can still occur in flight whether the batteries are "in-use" or not.

Mr.Conner has been misinformed or does not understand the nature of the charge/discharge system.
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  #305  
Old 03-05-2013, 08:11 PM
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Originally Posted by Spasso View Post
The only time the charge can be replenished is when the engines are spooled up, therefore the possibility of a malfunction (or over-charge) can still occur in flight whether the batteries are "in-use" or not.

Mr.Conner has been misinformed or does not understand the nature of the charge/discharge system.
I suspect that the batts can be charged while on a GPU buss. In fact, I'm guessing that batt buss voltage would be on the MEL for that plane, and if it's not at rated level a warning lamp will be present and the batt must be charged by either the engine or the GPU.
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  #306  
Old 03-05-2013, 08:11 PM
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Originally Posted by boxerman View Post
But one must question if Boeing made such amateur mistakes with the Battery cell spacing, what else have they put in this plane that is not well understood.
The mistake Boeing made was that they left the design up to the sub-contractor.

Quote:
Originally Posted by boxerman View Post
We know that the MBA driven design and production methodology of having subs do most things did not work out as planned for manufacturing efficiency, I wonder if the same is true for design flaws.
* Yes it is true for design flaws x 1000, in all aspects.
* This has been the major issue causing the production delays, over promising and under delivering by under-qualified contractors, going back three tiers in some cases.
* These aren't Toasters or Toyotas and to think you can use the same exact methodology in production is a mistake, a big one.

* Disclaimer: Opinions expressed above are solely my own and in no way reflect the official views of Boeing and it's affiliates.
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  #307  
Old 03-05-2013, 08:12 PM
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Originally Posted by Spasso View Post
More than likely.
The only time the charge can be replenished is when the engines are spooled up, therefore the possibility of a malfunction (or over-charge) can still occur in flight whether the batteries are "in-use" or not.

Mr.Conner has been misinformed or does not understand the nature of the charge/discharge system.
Or thye are all BSing trying to get the plane back into the air or Boeing is gone.
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  #308  
Old 03-05-2013, 08:13 PM
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Originally Posted by docmirror View Post
I suspect that the batts can be charged while on a GPU buss. In fact, I'm guessing that batt buss voltage would be on the MEL for that plane, and if it's not at rated level a warning lamp will be present and the batt must be charged by either the engine or the GPU.
The Engines or the APU, take your pick.
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  #309  
Old 03-05-2013, 08:15 PM
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Originally Posted by boxerman View Post
Or the are all BSing trying to get the plane back into the air or Boeing is gone.
LOTS of B.S.ing going on. In this case, thank God for the FAA and NTSB

STILL NO WORD ON THE CAUSE of these malfunctions, only the symptoms.
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  #310  
Old 03-05-2013, 10:41 PM
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Originally Posted by Spasso View Post
The Engines or the APU, take your pick.
Surely it can charge from the APU as it's embedded in the plane(somewhere). I just took issue with the statement that the batts can only charge with the engines spinning. I"m fairly sure they will charge on ground power using the GPU supplied. The 787 uses electric start, not air pressure, so getting the batts up and fresh is a priority(although batts are used to start the APU).
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  #311  
Old 03-06-2013, 01:42 AM
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Originally Posted by docmirror View Post
Surely it can charge from the APU as it's embedded in the plane(somewhere). I just took issue with the statement that the batts can only charge with the engines spinning. I"m fairly sure they will charge on ground power using the GPU supplied. The 787 uses electric start, not air pressure, so getting the batts up and fresh is a priority(although batts are used to start the APU).
Sorry for the misunderstanding. Yes I understand about charging from ground power.

What I was alluding to was Conner's statement that they weren't used in flight (specifically) and therefore not a hazard. In that case, the engines or APU would be doing the charging.

I don't recall the article mentioning this but the fire in Boston would have occurred while the aircraft was on Ground Power.
Rolling up to the gate plus the time to unload passengers which would have given the ground crew plenty of time to hook up.
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  #312  
Old 03-06-2013, 02:25 AM
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Lithium batteries can catch fire hours after they have been damaged. I don't know why this retardation happens, but this is known among the rc guys who use lithium batteries. Typically if they have been under mechanical or thermal stress. E.g. a lithium battery powered rc plane that crashes. Battery seems to be o.k. and is taken home. Laid down somewhere in the workshop at home and is forgotten. Workshop on fire. Happens from time to time.
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  #313  
Old 03-06-2013, 03:12 AM
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F1 ??

Not sure if the problems are the same but F1 teams spent huge resources on cooling the battery's for their KERS systems,and Boeing did not not spent enough or know enough to cool these battery's ??
the Williams F1 team had a KERS related battery fire after a race this year..where there is smoke there is fire..literally. I would have more faith in a system that formula one teams found a fix for than anyone else.
The Mclaren MP4-12C has a lithium battery, which is very small, but mounted in a case the size of the equivalent lead acid battery, as if to say "yes we want to save weight, but we know its going to fail, and you will want to replace it with a $100 battery instead of a $500 battery that is going to break again, so we will make the battery bracket big enough to fit the replacement"
Guess the Boeing subcontractors didn't bring that up....

I think we are still aways from this being "proven technology"
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  #314  
Old 03-06-2013, 11:31 AM
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Prof at MIT weighs in on batt fiasco. Interesting that my ideas seem to be backed up by someone at MIT. I'm blushing, no really I am.

MIT Professor: Battery Fix Could Ground 787 Until 2014 - Forbes
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  #315  
Old 03-06-2013, 12:38 PM
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Originally Posted by FERRARI-TECH View Post
Not sure if the problems are the same but F1 teams spent huge resources on cooling the battery's for their KERS systems,and Boeing did not not spent enough or know enough to cool these battery's ??
the Williams F1 team had a KERS related battery fire after a race this year..where there is smoke there is fire..literally. I would have more faith in a system that formula one teams found a fix for than anyone else.
The Mclaren MP4-12C has a lithium battery, which is very small, but mounted in a case the size of the equivalent lead acid battery, as if to say "yes we want to save weight, but we know its going to fail, and you will want to replace it with a $100 battery instead of a $500 battery that is going to break again, so we will make the battery bracket big enough to fit the replacement"
Guess the Boeing subcontractors didn't bring that up....
You cannot just plug lead-acid batteries into a L-ion system. Different charging, etc. systems. Electrical system must be re-done.
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  #316  
Old 03-06-2013, 03:22 PM
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Quote:
Originally Posted by chp View Post
Lithium batteries can catch fire hours after they have been damaged. I don't know why this retardation happens, but this is known among the rc guys who use lithium batteries. Typically if they have been under mechanical or thermal stress. E.g. a lithium battery powered rc plane that crashes. Battery seems to be o.k. and is taken home. Laid down somewhere in the workshop at home and is forgotten. Workshop on fire. Happens from time to time.
+1 On mine, the instructions are very explicit;

- Use only the "correct" smart charger.
- Only charge in a "battery bunker" or ammo-can.
- Store inside said protection.

Quote:
Originally Posted by FERRARI-TECH View Post
Not sure if the problems are the same but F1 teams spent huge resources on cooling the battery's for their KERS systems,and Boeing did not not spent enough or know enough to cool these battery's ??
*Very* different requirements; F1 stuff is designed to be charged/discharged *hard* - Much heat produced and many "duty cycles" just in one race.

Here though I *suspect* they're basically on a "trickle" charge pretty much all the time and almost never see *hard* discharging or the need for fast, big charges.

Plus, if one does go tits up (and it seems the systems do break) the guy's a little (soon to be a lot!) down on power - No big deal. 4-5 hours out over water is a little different of course....

Cheers,
Ian
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  #317  
Old 03-06-2013, 03:58 PM
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Originally Posted by Tcar View Post
You cannot just plug lead-acid batteries into a L-ion system. Different charging, etc. systems. Electrical system must be re-done.
You need another software. That's all. Even my 10 year old charger can charge almost everything. NiCd, NiMH, lead-acid, LiCoO2, LiMn, etc. pp. From tiny AAA to 100 Ah lead-acid. Of course if it is used in an airplane things have to be certified, but if in this case McLaren wanted to offer an exchangeable battery solution they could do this without hardware changes. I don't know if they designed their system this way, but in principle no problem there.
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  #318  
Old 03-06-2013, 05:43 PM
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PUBLIC DOMAIN SOURCE

THE SENTENCE IN THE LAST PARAGRAPH PRETTY MUCH SAYS IT ALL.

NTSB report on 787 coming Thursday | Business & Technology | The Seattle Times

The NTSB will issue an interim report Thursday on the lithium ion battery fire in January aboard a parked Boeing 787 Dreamliner

By Dominic Gates

Seattle Times aerospace reporter


The National Transportation Safety Board (NTSB) will issue an interim report Thursday on the lithium ion battery fire in January aboard a parked Boeing 787 Dreamliner at Logan Airport in Boston.

A month ago, in its last briefing, the NTSB said investigators had determined that the fire on the Japan Airlines jet started with a short circuit inside a single cell of the eight-cell battery, located in an electronics bay just behind the wing.

The NTSB has been trying to establish what caused the short circuit, but experts have expressed doubt whether that will ever be known for sure, given the level of damage to the battery.

There’s no indication that the interim report will provide an answer, though it may make clearer whether or not a definitive cause is likely to be identified later.

The report is “factual in nature and does not provide any analysis,” the NTSB said in a statement Wednesday.

Boeing’s 787s have been grounded since Jan. 16, when a second battery overheated and smoldered during an All Nippon Airways flight in Japan a week after the incident at Logan.

Boeing has proposed a fix for the battery problem — which, in the absence of a known root cause, attempts to address all possible battery system malfunctions. The company is awaiting approval from the Federal Aviation Authority (FAA) to implement that fix.

The FAA is expected to give its initial response late this week or early next.
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  #319  
Old 03-06-2013, 05:53 PM
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Originally Posted by Tcar View Post
You cannot just plug lead-acid batteries into a L-ion system. Different charging, etc. systems. Electrical system must be re-done.
On the Mclaren you just program the Battery control module with what type of battery is installed and it takes of it, as you say for the different requirements
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  #320  
Old 03-06-2013, 07:02 PM
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Originally Posted by Spasso View Post
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THE SENTENCE IN THE LAST PARAGRAPH PRETTY MUCH SAYS IT ALL.

Boeing has proposed a fix for the battery problem — which, in the absence of a known root cause, attempts to address all possible battery system malfunctions. The company is awaiting approval from the Federal Aviation Authority (FAA) to implement that fix.
Beer just came shooting out my nose!

Paraphrase: We don't know if/when the cell shorted. We don't know what the circuit was doing if/when the short happened. We don't know if it could happen again. If it happens again we will contain the failure to the battery compartment(we think).

The financial pressure must be incredible but that's no reason to do shyte like this.
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