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Re: [OM] The best laid plans of mice & men...

Subject: Re: [OM] The best laid plans of mice & men...
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Sun, 27 Jan 2013 08:59:30 -0500
The other problem with lithium-ion fires is that they can be cooled by 
water but not extinguished by water.  It just has to run its course with 
lots of water to cool the surrounding area.

Chuck Norcutt


On 1/25/2013 11:39 AM, Ken Norton wrote:
> Ever since we acquired a hybrid vehicle, I've been paying closer
> attention to current battery tech. I've come to a few conclusions
> which are being supported by some scary evidence.
>
> The Prius that we have does not use Lithium-Ion technology. Granted,
> the batteries are heavier, but they also are more stable and longer
> lasting. The thermal runaway, which really is an inherent flaw of
> Li-ion (and variants, such as Li-Poly) is something that can be
> managed but never entirely eliminated.
>
> Consider this scenario:
>
> The cellphone in your pocket contains a Li-ion cell. The cellphone,
> which is running, oh, say, the Android OS gets caught in a processing
> loop and proceeds to go into maximum current draw as a result. The
> battery gets hot and then at some point crosses a thermal threshold
> and proceeds to self-destruct. Next thing you know, you've got a
> conflagration in your pants that can't be explained by your virility
> and awesome personality.
>
> Consider this scenario:
>
> That hybrid or electric car sitting in your garage has less control
> and protection technology than what is in the 787's battery packs. A
> thermal runaway not only destroys your car, but the structure the car
> is parked in--your home.
>
> Li-ion is a fantastic battery technology. The amount of stored energy
> potential per kilogram is incredible. In theory, it is less harmful on
> the environment than the NiMH cells used for high-energy systems. One
> issue, though, is the internal-resistance. When a short develops, a
> Li-ion cell can self-destruct in a way that will take out the entire
> pack. When a NiMH cell develops a short, that cell will overheat and
> ignite, but the heat will generally damage the other cells in the pack
> where they go into an open state or otherwise fail. In this sense, a
> NiMH pack, while still dangerous, is self-attenuating whereas a Li-ion
> pack goes into a runaway situation until full destruction is achieved.
>
> I think I'll stick with the Toyota NiMH system for now. But I do have
> new dual-mode smoke detectors in the garage.
>
>
-- 
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