When a jumpstart goes wrong? Safety Question

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?

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u/calvinvb Dec 31 '23

Reverse polarity would burn those cables away instantly. Wouldn't take 10 minutes before you see it starts melting. Also nobody's opinion will help because damage has been done. Only "opinion" or i rather call tip. Is to not leave your car alone and stuff like this won't happen

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u/Ok-Needleworker-419 Jan 01 '24

Yeah and it would be throwing sparks the second you connected it backwards. There’s no way you connect it backwards and not realize it instantly

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u/calvinvb Jan 01 '24

Well if their battery was deas dead then in theorie it would do that. But then also it wouldn't take 10 minutes to do this damage and probably it would do more then just melting.

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u/Tylerdirtyn Dec 31 '23

OP wasnt there. Neighbor probably wasnt paying attention. If it was a poor connection to a dead battery it may not even spark at all, just slowly melt iver the course of 10 minutes. The only way they could have melted it with thin cables is by cranking the living bejesus out of the recipient car. OP said it was never even cranked. Logical deduction excludes the incorrect scenarios.