Sorry for the lack of info. Not sure I would need the extra juice as I have a 4000 watt on board genny and will have 200 watts of solar to charge with. I am just thinking ahead as the nights are already getting colder around here this year and I will be camping at 8500 feet for 2 weeks with no option to plug in. First time I will be using the trailer for this long in these conditions and I want to be prepaired as I can. I was thinking about throwing the 2 batterys in the truck and only using them if I needed to. I just don't want to be cold or frozen up.