Rodeo Isuzu Keeps Draining Four Batteries Can't Find Problem?

No one seems to be able to locate the reason why my battery is drained within a week. First it was a bad battery, then second bad battery, then the cables were repaired, then the alternator checked, then oh a door must have been left open after four new batteries no one can locate the problem. I just put in the fifth battery all was said to be fine, it's dead after taking a four hundred mile ride to bring it home, yep it died within a week.