When a jumpstart goes wrong?

[u/jhwalk09]

Neighbor tried jumping my wife’s ‘06 Nissan Altima, we left it for 10 minutes and came back and the cables had melted through the headlight of both cars and some of the bumper. I wasn’t there but thankfully they stopped their car and were able to disconnect the cables without incident. We noticed after there had been mice living in around her engine from the mouse poop, minimum the last two weeks. What causes jumper cables to do this? Something a rodent may have chewed? Definitely an issue with my wife’s car. Our poor neighbors have a newish midsized suv. My wife has also had constant issues starting her car, even with a new battery I got a year or two ago. Anyone seen this before?

[u/BAS316]

Your cables may be that thick. I know mine are. I've also seen cheap ass sets for sale and in use by various people that are not. I think the worst one I've seen said 10 or 12 gauge wire.

[u/voucher420 → u/BAS316]

I could see a cheap set of jumper cables doing this.

[u/IHaveNoAlibi → u/voucher420]

If they're trying to actively start the car with them, yes.

If they're just letting the battery charge through them, no.

It seems reasonable to assume that when they left it for a few minutes, and came back to it melted, it means they weren't actively trying to start it.

[u/voucher420 → u/IHaveNoAlibi]

Depends on how dead the battery was or if it was internally shorted. When you hook up two batteries together, they will transfer energy from the one with higher voltage to the one with lower voltage until they equal out. With lead acid batteries, the more they are discharged, the more current they will take. As they come closer to a full charge, they will not be able to draw as much current.

[u/YourInMySwamp → u/BAS316]

I’m not sure what mine are but I bought them from 7/11 when I was in a pinch recently and I highly doubt they’re that thick

[u/f0rcedinducti0n → u/BAS316]

12 gague wire would be a little anemic for cranking. However if you let it charge for 15 minutes and disconnected before cranking, it would work fine.

[u/BAS316 → u/f0rcedinducti0n]

Never said they wouldn't work. I personally wouldn't trust them though.