Found a 3.2 cubic foot Igloo refrig at Costco for $100 that has an Energy Star rating of 219 Kw per year. That is ~100 less than what has been on the market the last several years. Thought that was within range of being made workable for a van refrig. Thought I might be able to reduce that rating by 20-30% and then with a relatively efficient small inverter get something that would run off of my 12 volt batteries for a couple of days.
I over achieved
. Got a 60% reduction in power consumption. My modified refrig. uses 87Kw per year (on 110 volts AC) and that translates into 20 Ah per 24 hours of use at 73F ambient.
I have two inverters in the van, a 1000 watt Tripp Lite and 100 watt rebuilt no name. Both modified sine wave. Discovered that the 100 watt one that cost me $20 doesn't work. So have on order a 150 watt AIMS sine inverter with only 0.4 amp idle draw. Should work fine with the refrig. The max start up wattage I have seen on the refrig. was 130 watts that dropped to 55 watts in less than a second.
I estimate that the refrig [20Ah]w the AIMS 150w inverter [11Ah] should use about 31Ah per day at 73F ambient.
Just ran the refrig for 24 hours in the van using the 1000 watt modified sine wave Tripp Lite and it worked fine. Freezer section 22F and refrig section 43F.
Now have $113 into the project. $100 for the refrig and $13 for a 4'x8' sheet of 1/2" insulation. Not counting the $60 new AIMS inverter.