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/jhwalk09 Dec 31 '23

Neighbor who did it insists the cables were clamped right, I’m inclined to believe him he’s a handy guy, but thats what it looks like right?

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u/MarsRocks97 Dec 31 '23

Tight isn’t the issue. Each clamp MUST be clamped to the correct polarity. Mismatching will cause the cable to overheat and quite likely also ruin the weaker battery possible both batteries.

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u/jhwalk09 Dec 31 '23

That’s what I meant he insists he clamped em to the right ones, black to black red to red

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u/FirstWoodpecker2197 Dec 31 '23

If you're jumpstarting it's red to dead black to ground...