Tuesday, April 21, 2009

Funny and Informative Click and Clack

Dear Tom and Ray: Can you use a hybrid vehicle to jump-start another car? Recently when my girlfriend was visiting me in Cleveland from D.C., her car wouldn't start. The first thing I tried was jump-starting it from my hybrid. Before I knew it, there was smoke coming out of both cars! Naturally, I panicked and quickly disconnected the cables.

I soon realized that the insulation on the cable's pincers was melting and generating the smoke. I'm sure the cables were connected to both 12-volt batteries correctly. Any idea what might cause this? Happy ending: Eventually, we got my girlfriend a new battery, and she was safely on her way home to D.C.

- Tim

Ray: You likely used a cheap set of jumper cables. If you use really thin cables and send lots of current through them, they're going to get hot. There are ways to exacerbate the situation and make them get very hot.

Tom: If your girlfriend's car is much bigger than yours, her battery will try to draw a lot of current from yours. That'll generate extra heat. So will a failing starter motor; if her starter is giving out, it will keep trying to draw current until it either starts, melts or fries the wiring, whichever comes first.

Ray: And all that heat can set some frayed insulation a-smokin'.

Tom: It's possible that if you had left things alone, her car would have started before the fire did. But if you're not a mechanic, and you see smoke coming from the site of a repair you're attempting, abandoning ship is exactly the right thing to do.

Ray: Just to be sure, we checked with Toyota, which sells more hybrid vehicles than any other manufacturer, and it said that there are no restrictions against using the Prius, for example, to jump-start another car.

Tom: The Prius, like most other hybrids, has a 12-volt battery, in addition to its larger, hybrid battery pack. It's a small 12-volt battery, and it's located in the trunk. But there's a pair of jumper terminals, marked with plus and minus signs, under the hood, to allow the car to jump-start or be jump-started.

Ray: As long as that 12-volt battery is in good working order and is properly charged, it should have done a perfectly adequate job of jump-starting your girlfriend's car.

Tom: But despite that, you did exactly the right thing, Tim. You saw smoke, gave up on doing it yourself and threw money at the problem. Women like that. It shows that your judgment is stronger than your ego. I'm sure it added to your girlfriend's confidence in you.

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