I was looking at
THESE but I ended up mounting my battery inside the camper so the furnace keeps it warm. I may concider these when I do the 5th wheel. these are low power so you would definatly have to have the batteries in a insulated container for them to be effective.
you would also need somthing like
THIS to controle them.
2014 F350 6.7 Platinum
2016 Cougar 330RBK
1991 Slumber Queen WS100