I have a 120 volt fridge, one of those double the size of a dorm fridge in a compartment that we purchased at Sams Club, in the passenger rear compartment of our 5er. I ran a 12 gauge contractors extension cord from the front of the 5er, where the inverter is connected to 2 6 volt 208 amp batteries in series. I ran the cord down and under the rv and using zip ties, routed it high in the frame to the compartment in the rear. Ended up using about 45 feet of a 50 foot extension. Out of the inverter at the fridge I have 115 volts. We have never had a problem as once it reaches its cold temp, it will cycle. Worst part is start up of the compressor on the fridge but the inverter has never seemed to be bothered. We have boondocked for about 2 full days in the spring and late fall before using the genny to charge up the batteries and we usually run it about 4 hours. We start the charge when the batteries reach that magical 12 volts or 11.8 at the lowest.
Now we try our best to cool the fridge down before we leave and have cool drinks or whatever in the fridge before we head out. We have turned on the fridge on just the inverter and it cooled just fine and cooled down some pretty warm bottles of water and sodas in fact a rather fully packed fridge with 80 degree bottles of soda and water, took over 12 hours to cool them down properly. We usually fill the little freezer with the water bottles also and just let it do its thing. We have been more than satisfied with this arrangement and have been doing it for several years. I do get under the RV and check the zip ties and cable to make sure there is no damage and no danger of short often. I do disconnect the inverter 120 volt side when not in use to avoid any accidents, not just turn off the inverter but unplug the extension cable from the socket on the inverter.
I know, I know, using a contractors extension cord is not code, not proper, not kosher, not, not not, but it works and we keep a pretty good eye on it.
I hope this information helps.
2015 F-350 King Ranch
2015 Sabre Silhouette Select 312RKDS