Battery intermittently dead

My 2000 3.8 Impala has an electrical problem. Intermittently, after the car has been parked, the battery will completely drain. I replaced the battery because it had a bad cell about a week ago. Parked the car two days ago and now the battery is completely dead. Everything else seems normal with the car including the ISS problem, airbag light and the engine coolant issue. Has anyone else had a similar problem? Any ideas will be appreciated.

sounds like a short somewhere.Good luck finding it.Maybe you will get lucky and find that its just the light under the hood or glove box or trunk thats staying on.pull the bulbs and see what happens.How long does it take to drain the battery while sitting ?if it takes a long time like overnite its possibly a light or something.If it drains quickly its something that drains alot of amps like a starter or something.Lets face it these cars are full of electrical nitemares.And the dealers have all kinds of expensive reasons why.They will have you just keep changing parts until your broke or you surrender and get rid of it.