FW: Battery

[Mike O'Dell]

the chemistry system used in a lithium cell makes a *huge*
difference as to its willingness to hop up and chase you
around the room.

but yes, elemental metallic lithium is not to be trifled with
on any occassion.

The lithium ion cells using non-aqueous chemistry (ie, organic
compounds in a solvent) are the most energetic in terms of
energy density, power density, and potential for "high-speed
reconfiguration" if provoked. And of course, that's what everyone 
wants to use for battery life and weight reduction.

at the other end of the spectrum, the lithium metal hydride cells
are lower performance but also dramatically less likely to misbehave
even in the face of considerable abuse.

A123 went public at a nosebleed valuation based on their "novel"
"high energy" cell chemistry. an electrochemist i know looked at
the A123 system for a potential investor and his report did not
discuss whether they would have a catastrophic even, but rather how long
it would be before it happened. And lo, it did come to pass.
The Chevy Volt did not ship with the A123 battery that was originally
announced.

I'd dearly like to know whether the 787 lithium-ion battery systems
actually saved any weight over NiCd or AgO2 once they had to
package them in a fireproof safe.

Boeing had another 787 battery fail a week or two ago, but only one
cell "vented"(!!!!!) and the packaging contained the event. Boeing
made a point of declaring victory. Talk about inviting a lightning
strike!

As for the Tesla batter fires, those that have occurred have
resulted from significant pieces of steel penetrating the floor of the
vehicle and then the battery assembly deeply enough to puncture cells. 
given how that structure is constructed, that is *not* trivial. 

the sad fact is that hydrocarbons are an extremely efficient albeit
non-reversible way to store energy, and that a reversible process 
for storing even a fraction of the same energy per gram of chemistry
is going to be something you should think *several* times about 
having in your pocket. if something goes wrong and the energy
gets loose, you will *not* want it close to your body!

     -mo