Short term, the 15/20 hookup will keep your battery charged to run the furnace. Long term, if you are thinking of any dry camping in cold weather, battery upgrades are in order, such as dual 12v in parallel or dual 6v in series. We camped in Grand Teton and I swapped the OEM Group 24 battery for a group 27 plus LED conversion and dry camped for 4 days with light furnace (set at 50 with blankets). I didn't know about volt meters at the time, so it was risky, but we had enough to bring in the 2 slides and raise the landing gear on the last day. I have since installed dual 6V golf cart batteries.