I'm pretty sure that even you have electronics hooked up to you car but their not on, doesn't mean they aren't running through the battery. You might want to have your battery tested to make sure. You may need to get a new alternator that can power more wattage. For example, the amp I have in my car will still use the battery even though the car is off. There's a cool gadget at Kragen for less than $20 that you can hook up under your hood. You can mount it anywhere. It's use to turn off all power in your car when it's off whenever you want. Let us know what the real problem is if you find out! Good luck!