My Dodge Neon is a vampire

I have a 2005 Dodge Neon (which I normally love) but this will make the third battery within 2 years that I’ve had to buy. It just happens out of the blue, one morning (or evening this time), I will go out and it won’t start. It will turn out that not only is the battery drained but dead, so dead it can not be revived. What is causing this? I’ve taken it to 2 dealerships, and they have no idea either.

Use the Search function, above. In the keyword space, place “battery drain”. There will be a LOT of posts on the problem.
ADDED later: Motors, or fans, which come on, and go off, at intermittent periods after engine shutdown can rapidily drain a battery like a thief in the night. I’ve seen/heard radiator fans come on hours after engine shutdown. Change the radiator fan RELAY, and it doesn’t do that any more.