Stephen A. Lawrence
Sun, 11 May 2008 19:29:39 -0700
thomas malloy wrote:
Rick also mentioned Li ion batteries. He said that Energetics will never produce a charger for them. Apparently they tend to catch fire, or explode. Either event is not conducive to getting a UL seal of approval.
Of course we've all heard about the flaming power books which Apple was (briefly) known for.
I have been told that this issue was due to a manufacturing problem in lithium ion batteries. As I understand it, the plates in these cells are very, very close together; microscopically close together, in fact. But as long as they don't actually touch, all is well.
However, the battery plates are rolled out -- pressed between rollers -- during the manufacturing process. The problem was that the rollers used would start to wear, and tiny splinters would be spalted off them. As it was described to me, they're steel rollers, and they continued to look brand new and pass any ordinary inspection; the splinters were microscopic (or nearly so) and so were unnoticed.
The splinters ended up embedded in (some of) the batteries. As long as they weren't shorting anything important all was well and they could be ignored. However, under stressful conditions -- and, in particular, under the somewhat higher voltages induced by charging -- the splinters would "stand up", perpendicular to the plates. At that point, in some cases, some of the splinters would be long enough to bridge the (microscopic) gaps between the plates. Voila, internal short! ... followed by overheating, fire, or, conceivably, explosion.
As I said, I didn't read this anywhere; it was *told* to me, by someone who is an expert on electric car conversions (he's done a number of them, so he's a de facto expert). He is not, however, an expert on batteries. I haven't googled the topic to double check the information, so take it for what it's worth.