apu problem

So im taking my week vac and have the truck at the house, turned off apu for then night, went to start truck for a min....battery was dead put the trikle charger on it and got it running got the apu on and ran it with ac on for about 2 hr but now the battery died again apu wont get enuf power to get it going again, so its back on the charger but any help? Was just in shop and checked out a couple days ago

 

Nope jus keeps trying to start, have the alternator on apu changed out 2 months ago

 

Dont know if they checked it, was the ta in fort bridger,wy they had it for 4 hrs dude said he checked everything

 

Belts are tight ill check the wires here in a few, thanks

 

Ya it sounds like a good start just cant stay started ill half to look fir the air filter