RVCrazy, in your scenario, I suspect 6 hrs would be fine. It will likely stay cold enough for that period of time without power (if you keep it closed). You could also power it with an inverter - probably a true sine wave version. Your battery bank is probably 200Ah which means you have 100Ah of usable power. I do not know what the power consumption is of that refrigerator but you likely have enough power available (assuming there are not other large loads). If your battery bank is charged while driving, you have even more power available.