Battery help.. question for the battery experts

tow vehicle is brand new 2013..so brand new battery. im the only one with a camper that I know... if it doesn't hurt the camper to have two batterys hooked up and as long as it still charges fine with two batteries hooked up then I will probably just hook up both.. even if its wasting two batteries as I don't use them..LOL... better then rotting on my front porch... oh well... leave it to me to make a mountain out of mole hill...oh well...