Dead Battery

Look for electrical parasites like an underhood light not going out, couteousy lamps staying on, radio performing something it shouldn't with the key turned off and so on...................

I recently had a similar problem. Turned out to be a bad Alt. It was grounding, causing a drain. I would park the car overnight and next morning it was dead. Got a new Batt and same thing. Easiest check is to use a digital multi meter on the batt. With the car off, you should get a reading of 12.6v, with the car on, it should be in the area of 13.5v. Recharge your batt and check it. If you dont have a multi meter, you can get on from walmart for 10.00 or take the car to your local parts store and have them check the whole charging system. Its free. At least you'll know whats going on or if thats where the problem is. Good luck.

not saying it is the cause, but a bad alt diode will drain a battery overnight.

good luck.

If it acts like a drain it's most likely the alternator.. (assuming the battery is good and holds a charge)

I'm with HISSIN50 on this one..