Many people will say that you need to go with two 6-volt batteries in series. We just bought a Trojan Deep Cycle Group 31 12-volt. It is 130 amp hours. We can generally get 3 days of dry camping out of this battery (just DW and I). But we turn our heat down to 50 at night. The furnace fan will eat up your battery. Get a dog and 2 extra blankets!
We also converted to all LED lighting and that also makes a BIG difference. .4 amps instead of 2 amps per fixture. If you camp where generators are allowed, there is really no need for 2 batteries IMO. If we run the Honda for 30 minutes in the morning (coffee, hair dryer, etc.) and for about 60 minutes in the evening (microwave, etc) it seems like we can dry camp easily. Our tanks fill up before we run out of juice. It is tougher when you have kids though. More power inevitably gets used. (The tanks also fill up quicker!)
Most trailers come with a group 24 though and they generally aren't very capable. But maybe you can live with it. Otherwise you will be getting rid of a brand new battery!!
2012 F150 FX4 Ecoboost, 2016 Surveyor 274BHS
2003 Yamaha FJR1300, Demco Premiere Slider
1969 John Deere 1020, 1940 Ford 9N, 1948 Ford 8N
Jonsered 535, Can of WD-40, Duct Tape
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