Random battery drain on '00 Durango

So this is an odd problem that's been going on here. My mom's 'new' '00 Durango with about 120K miles on it. Over the past 2 months during her ownership this has happened twice. Basically overnight the battery seems to drain completely. Not even enough residual juice for a dim light somewhere. Put it on a battery charger for 10 minutes or so and it's enough to get her started and let the alternator get the battery back to a decent voltage.

First time around she had the mechanic at work look at it and first thing that was noticed is the last owner made a hackjob of the rear end wiring by splicing the trailer hitch wiring harness directly into the tail light wiring and such by hand. He immediately cut the wiring from the hitch controller 'thing' and the wiring to the tail lights and his tester bulb went out showing there as no further MASSIVE drain on the battery.

That was about a month and a half ago. At that time she had replaced both the battery and the alternator. Go out today and attempt to start it and there's nothing. No guages, no lights, not even a slight attempt to crank over. And it's only been sitting since about 8 last night and it was running fine then. Put it on the charger for 10 minutes and she kicks right over.

I'm lost what else may be the issue here. Other than this and more of an annoyance with the rear right passenger door automatic lock, this vehicle runs great and has no problems. If anyone has any insight, that'd be great.

On my 99 durango, the hood light came loose from it's mount on the hood.
This allowed the mercury switch to turn the light on as long as the hood was closed (it's supposed to turn on when the hood is open).
So, whenever I would open the hood to troubleshoot, the light would be off, and therefor the problem was gone.
It's not likely to be your problem, the light would only drain the battery after about 2 days, your's sounds like it's a heavier drain, but worthy of checking.

Well, just got it back from the shop today and the mechanic had found out it was the rear window wiper which had never worked since we bought it anyway. Apparently it had gotten stuck into a non-parked position and had been continually trying to return to that position even with the key off. Disconnected the motor altogether and it's back to normal. :)