Ok people, so here's my problem: A while back I left my car with the map light on for like 6-7 hours while I was at work and obviously my battery drained. So my friend (Evo 8) tried to help me jump-start it but wouldn't start. So my mom brought her truck (Nissan Pathfinder) to help me and started up right away. Ok since then, everytime I'm at cruising speeds and i drive around for like 15-20 mins with my stereo kinda loud, the battery drains. Now it doesn't happen if I jump on the freeway or anything but yeah, it happens constantly. So i went to Autozone to get my battery checked and it was good. The guy said it could probably be a short circuit but wasn't sure. Can it be my alternator that's shot? Because the battery doesn't always drain, but it does. Please auto-electric people, help me!!!