2 group 27 deep cycles,camper is brand new ,only 2 months from the factory,i keep it fully charged,but the o2 detector and some other stuff run it down while it's parked at work during the week and no,i can't plug it in while it's there,and the plug runs the camper lights ok.its a camper,not a travel trailer.the truck is equipped with the integrated trailer brake and the tow package.i've also pulled a dump trailer with it and the lights and brakes worked that time. i try to charge it when i get home from camping but it bleeds down during the week it sits,and i'm usually travelling 3 to 400 kms per trip and that should recharge them,so all i can think of is it's a fuse or relay that's not working.