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Charles Murray
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Re: Liquid cooling for Li-ion???
Charles Murray   3/11/2013 10:26:06 PM
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I've gone through the NTSB's interim report, Jeffrey, and there's no reference to earlier high temperatures, so I can't answer the question. For what it's worth, though, The Wall Street Journal reported that the temperature during the JAL incident hit 1,250 degrees F.

Charles Murray
User Rank
Blogger
Re: Tried, Tested and True...
Charles Murray   3/11/2013 10:22:45 PM
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Regarding a contribution to the correct political campaign, GTOlover: LaHood is a Republican working in the Obama cabinet, so I'm not sure which side would be the "correct" one.

Charles Murray
User Rank
Blogger
Re: idea
Charles Murray   3/11/2013 10:17:35 PM
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Agreed, ChasChas. All of these troubles do beg the question of whether it's really worth it.

Charles Murray
User Rank
Blogger
Re: 787 batteries need liquid cooling
Charles Murray   3/11/2013 8:01:36 PM
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Still don't know, Cabe. When the FAA approves it, Boeing will talk about it. Until then, details are scarce.

Cabe Atwell
User Rank
Blogger
Re: 787 batteries need liquid cooling
Cabe Atwell   3/11/2013 5:20:23 PM
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Any news on the Boeing "permanent fix," Chuck?

C

ChasChas
User Rank
Platinum
Re: idea
ChasChas   3/11/2013 1:07:03 PM
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More than the words out of my mouth.

By time you add the cooling, you have the weight of a safe battery.

Like you say, leave the power density on the ground.

g_ost
User Rank
Gold
Re: Tried, Tested and True...
g_ost   3/11/2013 12:45:11 PM
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Tmachell
User Rank
Iron
Re: Tried, Tested and True...
Tmachell   3/11/2013 12:11:59 PM
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Heh...heh. Yeah, but if the ins. co. found out that you flew knowing the published issues/dangers, they might not honour the claim, many don't cover suicide!

I was thinking that instead of cooling or smoke venting systems, they should just make a break away battery with a trap door and drop it out the bottom of the aircraft, that'd do it right? It could catch fire at anytime then. Let's face it, how many times do we actually need only battery power... :-) Yeah, the battery burning at terminal velocity through moist air is kinda like a meteorite. Funny, mention an idea like that and everyone would laugh, but venting smoke is a viable cure?

But those extra large windows and extra cushioning with wine holders in first class sure makes me feel better about flying the DLiner.

Jeffrey
User Rank
Bronze
Liquid cooling for Li-ion???
Jeffrey   3/11/2013 11:55:20 AM
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I'm dubious even about the need for liquid cooling in a case like this.  Correct me if I'm wrong, but do we even know that the cells reached a high temperature PRIOR TO the fires?  This is critical.  I assume the battery management system monitors the cell temperatures.  If it does, and the cells had reached a high temperature, I'm guessing this would have been announced already.  And if the problem occurred without a prior high temperature, then something else, presumably internal to the cell that caught fire, was the cause, and liquid cooling would be superfluous.

bdcst
User Rank
Platinum
Re: 787 batteries need liquid cooling
bdcst   3/11/2013 11:38:43 AM
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Liquid versus air cooling?  The present battery has no effective cooling system of any kind as far as I can tell.  The case provides conductive cooling and any outside air provides passive convection cooling of the case and that is it.  The cells could bake each other with no effective cooling within the battery.

Boeing needs to maintain the energy to weight ratio.  So, no other battery chemistry or more complex cooling system is practical for their design goal.  Internal heat pipes connected to a cold plate on one side of the case could help reduce internal cell temperature but would add weight and would most likely require active cooling outside the case.  So, it looks like they'll be opting for a more fireproof containment, more space between cells and maybe an external venting system to keep the case from rupturing and smoke from pouring into the cabin.  Band-aid approach?

This alone will not prevent catastrophic battery failure but will permit them to live with occassional battery failures without endangering the aircraft.  Or at least that's what they may be hoping for.  The time bought will permit them to eventually phase in a full redesign of the battery system.  That's what I'm hoping for.

 

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