Car Talk

December 2003

Dear Tom and Ray:

My daughter's boyfriend bought a used car from a dealership. The dealership had a 127-point check to ensure that its used cars are safe to sell. After driving it for a month and a half, the battery needed to be jumped. A friend of mine helped the owner of the car jump the battery from another vehicle; the car wouldn't start. So, they removed the battery and set it on the ground. A while later, one
of the guys bent over the battery and merely put his hands on the sides of the battery, and it blew up in his face, causing the loss of his eyesight in one eye. Why did this battery blow up? It was not dropped. It was in a Volkswagen Passat and was an Autobahn battery.
-- Ana

RAY: Yeesh. That's awful, Ana. It's very rare that batteries actually blow up. But obviously, it does happen occasionally.

TOM: It has nothing to do with the battery being on the ground. The reason batteries explode is that dead or dying batteries can emit hydrogen gas. And we all know -- see "Hindenburg" -- that mixing
hydrogen gas with a spark is a bad idea.

RAY: So, the question, in your case, is where did the spark come from? Was anyone around the car smoking? A floating ember could easily have provided the spark.

TOM: Or was someone wearing polyester pants? If your friend had built up a static charge walking around and then touched the battery, a spark could have jumped from him to the battery.

RAY: So we don't know what provided the spark. But something ignited the outgassing hydrogen, and that's what caused the explosion.

TOM: Your letter is a reminder that too many of us (including me and my brother sometimes) are often guilty of neglecting to wear our safety glasses. After all, they're uncomfortable, they seem to come
from the factory all scratched up, they fog up quickly and they make you look like Mr. Magoo.

RAY: Which is an improvement, in my brother's case.

TOM: But this is a good reminder that safety glasses really can save your eyesight. So wear 'em.
Beat up old car

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