This is an old thread ... but ... did you install batteries inside the bed of the truck? If so ... how do you vent them?
There's no need to vent them. That's almost entirely a bit of old lore. not an issue with modern "sealed" batteries. The miniscule amount of hydrogen they might produce isn't going to be trapped by a camper-shell's design. And especially not if a human is back there with a window / vent open