Converting our FWC Shell to Dual Batteries

After installing the fridge, we started having furnace issues. Turns out, the Dometic furnace stops working below a certain voltage. A voltage we seemed to get to around 3 AM with the new fridge. You know, the best time start freezing and futz with things like that.

So our single house battery without solar (79AH) from the factory left us making the choice at night of either running the fridge or the furnace, but not both. You can imagine how long that lasted.

In my very rushed research between trips to get this resolved, I found that the “best” option is to install two six-volt batteries in series. Six volt batteries are great deep cycle batteries and enable you to pretty reasonable achieve more than 200 AH of power. The downsides to this setup are that, (A) the batteries are very unlikely to be available locally (either where you live or where you’re traveling), (B) they’re expensive, and (C) in a pinch, you need both to jump a vehicle (or if one cell dies in one, you no longer have house batteries at all).

Like all thing in life, we compromised. The original plan was to install two group 27M batteries in the factory cabinet of our Shell model. Be warned – they do NOT fit. So instead we had to settle with the factory installed group 24M size batteries. Two twelve-volt batteries installed in parallel doubles the AH rating of our original setup from 79 AH to 158 AH. Not amazing, but twice as good and for about $350 all-in (about half what a six-volt setup was going to cost). As for what batteries we used — I referenced my own guide on that from a few years ago.

I think a solar setup is in the works over the winter when we slow down on travel.