Battery goes dead after about 3 days.

Could just be a weak battery not holding a charge. A battery will typically start to lose health after about two years of use. Other things we have seen are stuck relays running fuel pumps or air suspension. Possibly a trunk or glove box light stuck on.

there is a 15 amp fuse in the fuse box in the engine compartment check and replace that fuse. If it si blown out the alternator will int charge the battery.