when I mean that something is shorting out I mean a power wire that is going to ground before your amps not that your amps are still on after you turn off the car. Your problem is that something is still pulling electricity from your car even after it is off. I know that is re-stating the obvious but that electricity is going somewhere. If you really want to know that it's not your battery then pull the negative cable off the battery overnight. When you hook it back up in the morning and if the car starts then you can be sure that it is not your alt or bat.
Mentally go through your car listing all the electrical systems you have installed. That would be any stereo, lighting, radar detect., or ect. that did not come originally on the car. Then look at all your wiring to those systems and check for chaffed or loose wiring.
Face it Electrical gremlins like this take time to find. I wish I could tell you exactly where the problem is but that's just not possible. Your going to have to go system by system looking for the problem. But like I said start with aftermarket electrical because those tend to be where the problems lie.
