What would cause jumper cables to melt?

[Louisa]

Anyone know what would cause jumper cables to melt when jumping a car? My sisters vehicle has been having issues with the battery dying and she is just finding out its either the starter or alternator probably...but anyhow, I was present (and MY jumper cables were used!!) jumping her sedan with a Suzuki sedan and she went to turn her engine on once they were hooked up and nothing happened, then smoke started coming off the black terminal of her vehicle and the whole cable started melting up before my eyes! turned off the suzuki (the good car) and took the cables off, they eventually cooled down but they are ruined, and it was a frightening experience!

And yes they were hooked up to the right terminals (pos and neg) because I know we checked and double checked that. Any ideas? Is there any damage that could have been done to her car? its still dead as of now, shes scared to try again which I dont blame her, we're going to call AAA. The suzuki is fine, it fired up and sped off down the road.

Just wondering if any of you auto-savvy members might know what went terribly wrong? 

[JoeF]

Louisa, You have to be very careful when jumping a car or you can fry the elcetronic components.

Here's a link on how to properly do it. http://www.carbuyingtips.com/jumpstart.htm

NOTE:  If the cables are real warm and you're not having success, it's a sign that your jumper cables have a problem. If they warm up, it means there's too much resistance in the line. There should be very little cable resistance. If the jumper cables are frayed or rusty at the clamps they won't work.

[Savage]

I've found that when the cables get hot, it's because there is more current needing to be transfered then the cables can handle.
They come in many different thicknessess, the cheaper ones that are ussually about 5-10 dollars are ussually 10 or 8 gauge, which is very missleading because they are actually very think. The better ones like 2-4 gauge are anywhere between 40 and 70 dollars a set.
 They transfere more juice and tend to start cars much more quickly.
 Best thing you can do when using the cheaper ones. Hook them up correctly, and let the car needing to be jump, sit there for a few minutes while the running vehicle is running, and it helps a little to give the running car a little extra throttle.
 Ussually, if the battery in the non-running car is not completely dead, you can get it started after about 5-10 minutes idle time like this. IF your cables get hot while attempting to start the other car, STOP trying to start it, and be careful, those cables can get REAL hot and burn you, even if your just trying to disconnect them.
 Also, Alwasy, Always Always double check that your not crossing the cables/batter terminals. You'll blow out a wiring system and a hard to find fuse. (been there, done that)