Quote Originally Posted by stealthee View Post
Alternator isn't going to drain the battery when the car isn't running. The alt basically either charges or it does not charge when the car is running. It is not going to drain the battery either way, it just won't charge it.

You might have a faulty battery. Need to have it tested to make sure the CCA's are up to snuff, and to make sure you don't have a bad cell.
Wrong.

An alternator can back drain a battery when it goes bad. Simple test is disconnect alternator overnight an reconnect. If battery holds charge its a bad alternator. We have run into this a few times. Alt checks out fine and charges great yet battery still goes dead.