Jon Smith writes about battery pyrotechnics:
> a friend of mine has a problem with a battery for a Ford Escort (sorry),
> although the type of car isn't really important, it's about batteries.
>
> He bought a new battery the other day, connected it up, tried to start the
> car a couple of times and it turned over okay (it didn't start for some fuel
> related reason or other). Then, while trying for the fourth time he saw a
> big spark and the positive terminal on the battery melt! I mean the metal!
Hmmm, must have been a "high impedance" (couple of ohms) connection at the
battery post/clamp interface - did your friend clean the post and clamp
thoroughly before connecting them? It doesn't sound like it.
> I've had a look at the car and agree that it's pretty hard to connect up the
> wrong way round and we treble checked the battery is of the correct type.
Hooking up the battery backwards probably wouldn't have hurt it (the battery),
but all the electronics in the car would have gotten toasted. I don't think
this was your friends problem.
> [...] We were told by a guy who appeared to be about 15, who is apparently
> the manager, that the terminals wouldn't melt because there's something
> inside which, in the event of an internal fault, limits the damage to inside
> the battery (?) so it must have been my friend's fault.
Horse feathers! This guy probably knows about as much about batteries as he
does about cars! (I always find it funny (ironic) that car knowledge isn't a
requirement for employment in places like this, at least here in the US.)
If there were some kind of internal limiting in a car battery, then you would
never be able to draw the 50 or so amps needed to crank the engine! In much
smaller batteries, like those used in portable video cameras, there is indeed
a sort of a thermal fuse that temporarily "opens up" in the event the battery
is externally shorted, but this has nothing to do with car batteries!
> I'd have thought that if this was the case and the battery suffered such
> major external damage that there MUST have been an internal fault.
No, the problem had to be external, maybe a defective battery post. But if
your friend didn't thoroughly clean the connections, then it likely *was* his
fault!
> Does anyone know anything relevant about the internals of these things so
> that we can go back to this guy?
Good luck!
Pat Vilbrandt Fluke Corporation Everett, Washington USA
pwv@tc.fluke.COM or: { uunet, uw-beaver, sun, microsoft }!fluke!pwv
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