H3 battery dead after a few days of not driving and can't be explained by anyone... Don't what to do?

Seems you have a dead battery. Could be anything related to the charging system (alternator, control, wiring) or the battery itself. It takes a methodic process of testing to determine the cause(s).

Start by having battery tested and charged. If the battery checks ok and holds a charge then "likely" the problem is with the charging system, but it's a multistep process of elimination and very few parts store do a complete full load battery test.

If the battery test fails then you'll need to replace the battery and then promptly have the charging system tested to verify its working or you'll have another dead battery.

Once the battery and charging system has been verified functional you need to have a parasitic current test done. Excessive parasitic draw can ruin a new battery in a few months depending on your driving habits. Is this a daily driver or every other week or longer?

Charging system not working properly have your altenator checked

Try charging the battery a bit by snaking the positive jumper cable underneath to the starter post where the big cable connects, and the negative jumper cable to a good ground on the frame.

Battery Disconnect or Replacement Problems

it sounds like a faulty battery

You need the dealer to sort this out.

you probably have a short in the amplifier under the driver's seat. I had the same problem. Bought mine used, but the amp had water damage due to the vents for it on the left side of the driver's seat letting in water, probably snow or something that fell in there. Was $1200 to replace. Basically your car will be fine for a couple weeks, maybe a month then the battery will die.

As it's a brand new vehicle, it will be covered under the Manufacturer's Warranty. Call the Garage that you bought the vehicle at and tell them to come and pick it up and have the fault fixed under warranty. PLEASE DO NOT try to fix anything yourself and do not let anyone else other than the Manufacturer's representatives work on the vehicle otherwise the Manufacturer may void the Warranty.

The batteries they put in the trucks from the factory ****. I went through 3 of them under warranty, they lasted 6 months a piece.

I did research to find who made the factory model. I found an alternative manufacture and bought their battery and I have not had a problem sense. I bought a Duralast from auto zone.