battery drain overnight

we are having problems with a 2000 Tib. one morning every few weeks the car is dead. the battery has drained its power. you can charge the battery and youre good for a few weeks more. it has happened about five or six times the last few months. ive checked the battery every once in awhile and its always good. ive replaced it twice, still the same problem. cleaned the cables and double checked the connections. its happened in all weather, rain cold hot dry.. it dosnt seen to be weather related. my first thought was the door not shutting good and the dome light stays on overnight. i have stressed the importance in making sure the door shuts and the dome light is off. she says she double checks it now each evening. it still has happened a couple of more times. is there a relay that may stick ever so often and drain the power in a few hours? is there anything else that may power on while the car sits? it has no aftermarket equipment such as radio, lights etc. it is over all great car, it starts great every time execpt for those certain mornings. Help!!

check the alternator.. most likely its dead if its not recharging the bat every time u run the car...

agreed, alternator might be dead.

Its not the alternator. I have the same exact problem on the same exact car. I had the electrical system checked and the alternator is charging at 100% with a brand new diehard. One week later, the car refuses to start without a jump.

There are 2 battery cables (1 thick 1 thin) that connect to the pos terminal. I put a meter on the thin cable and noticed a drain, so I attached a kill switch to the thin one. This worked for about a week. After sitting for about 3 hours, the car wouldnt start, even with the kill switch.

After taking it to Hyundai, they discovered that the fuel pump was failing intermittently. As it got worse, it required more power to operate and a jump would usually start it. Eventually the jump didn't even work. In short, a periodically working fuel pump mimicked a drain on the battery. Weird eh?

Yeah, definitely doesn't sound like an alternator. If it was bad, you wouldn't be able to go a few weeks at a time or on any long trips without it dying.

Must be some kind of drain on the battery. If you've ruled out the dome light the only other thing I can think of right now is the headlights. I know on my Elantra if you leave the lights on and turn off the engine it looks like the headlights turn off (and the main ones do) but the parking lights stay on, which can drain the battery in a couple of hours.