07 Avalanche Battery

My dad has an 07 Avalanche that is on its 4th battery now. Dealership can find absolutely nothing wrong with it. Anyone seen similar issue or have any ideas? Any help appreciated.

My dad has an 07 Avalanche that is on its 4th battery now. Dealership can find absolutely nothing wrong with it. Anyone seen similar issue or have any ideas? Any help appreciated.

What is failing on battery?
Dead cell or just dead or running out of acid?
What is the charging system voltage?
MT

The only thing I can think of that the technician at the dealer may not have thought of is the under-hood light. If it is parked on a steep enough hill, it is possible that the switch is turning on. That, of course is assuming it is the old mercury switch and not some new design using a pin switch, etc.(can't say I've seen an '07 yet). When doing a parasitic draw test, most technicians will remove the bulb to get an accurate reading and not give it a second thought.

If you determine that the switch is allowing the bulb to come on too soon, just bend the metal to the point where it will turn on just before the hood is in the full up position.