We have a old 120v, 3.3 cu ft, Haier dorm type refrigerator. I got it back from my daughter years ago after she graduated from college. I've done a solar test on it before, but never with a good battery. Our 14 year old, mopar truck battery finally gave up the ghost, so I replaced it with a fairly inexpensive, but looks pretty good, RuralKing (Exide) Heavy Duty Farm Battery ($80). I've built my second 50 watt solar panel to go along with my factory built 50 watt, but decided on this test to just use the single factory panel, the new battery and see what the system is really capable of. I have a cheap HF 2000 watt, MSW inverter, so efficiency isn't great, maybe around 75% at best.
Started everything yesterday at 6am. Had a full charge on the battery. Sun wasn't up yet. Took the fridge down to 29 F and set it there. I use a wireless digital thermostat readout to monitor the temp. Finally got enough direct sun by about 9am and kept the panel on the sun until I lost direct sunlight about 6pm (lots of trees here). Daytime temps hit 85 F. Kept the system running through the night. It has been foggy so far this morning (about 9am), but the panel is generating some power. Battery level never dropped below 12 v overnight, fridge temps never got above 33 during the day. I'm going to let it run another 24 hours to see what a single panel can do.
Why do this? I think I originally paid about $80 for the dorm fridge in 2004. I think it paid for itself in 4 years of college, but I'll keep the cost at $80. New battery was $80. Original price on the factory panel was about $80 (seeing a pattern here?). Charge controller was $15. 2/0 wire from battery to inverter was $15. Cost of the PD045 panel/converter was $10 at junk yard. So, all in, over the years, I've got about $270 in my fridge/charging system. If I add in the cost now of the new panel I built (50 watts), it is $53. So for $325 I have a 100 watt system, with a fridge that can act like a freezer. I've test run it down to 17 F for a day running on house supply in the past. Remove the original cost of the factory panel and the fridge, since I already had them, then the cost is $165. Not too shabby.
Oh, and finished up Conch Fritters strip-down / re varnish. Will do some pics when the sun comes out.