I actually put in four deep cycle 6v golf cart batteries. Wired them to provide 12v to the system. Works great, with our 2000 watt inverter.Not sure what CF your Norcold is, but our fiver is equipped with a large residential frig (no propane). When we are not plugged in it draws 12volt power from two deep cycle batteries. It will easily keep that frig running for 8 or 9 hours on the road or overnight. Before spending a ton of money on different type batteries or additional solar I would try a couple marine deep cycle 12 volt batteries.