Bad wires or battery interference?

On our recent trip to Denver I tried playing music through the stereo using two different tablets. It played for a few seconds then went to so much static as to be unplayable. It didn't matter whether the tablets were plugged into a power supply or not.

It wasn't (and isn't) a big deal since we have the CD changer and usually carry a bunch of CDs with us all the time. I'm just wondering if it's most likely a bad wire in the car or it's interference from the car batteries. The same tablets and connecting cables all work perfectly in the house.