Using 12V DC on the 3-way refrigerator is a losing proposition other than when driving. They go through more than 15 ah which means 120 ah in just an 8 hour overnight sleep before moving on that you might do at a Walmart. That much would deplete two AGM or lead-acid batteries. So, if you add more battery or solar then your logical choice is to go to a compressor refrigerator that would go through about 90 ah in a 24 hour period. A 3-way needs the propane option no if, ands or buts, IMO. In effect, you are in trouble if your propane is not working.