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.
--
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
--
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