mr_andyj wrote:
200 watts of solar and 2 GC batts will run indefinitely on a DC Danfoss style compressor fridge.
Gdetrailer, yes, your setup works, but the reason it is not favored by many is the residential just pulls a lot of amps, will shorten the battery life as a result, and as you say, 2 days is it, 4 with your 300watts.
Your setup is great for weekend warriors, but the power usage is so much higher that I dont recommend it myself. Everyone wants to trump their own horn I guess.
My first camper I tried a small residential fridge and inverter. I had 3 batts. It worked great when new, but over time the batts lost life and the fridge would run them down quicker and quicker. The inverter, which uses power just being on, had to be on all the time and loses efficiency through its loses, and eventually when the batts did lose SoC thee was not enough to start the little compressor, and the fridge was of no use until I charged batts back.Not a big deal, but those batts did not last as long as I would have hoped; back then they were cheap is the good part.
Now I prefer the Danfoss compressor fridges. Expensive, yes, but a lot more ideal for those not willing to compromise function over dollars. Im cheap but a few things I will not compromise on. The fridge is one of the cherished items in my camper.
3 batteries?
Gonna have to assume you were using Group24 or Group 27 12V combo RV/Marine batteries..
That was your problem.
RV/Marine combo batteries are simply not up to this task, group27 typically is 80 Ahr each x3 = 240 Ahr.
But wait, those combo batteries are rated at only 20% of the capacity being used for rated life.
That gives you a measly 48 Ahr..
Each time you exceed 20% of the capacity you kill battery life.
My Sam's GC2s gives me 215 Ahr, but since they are designed for extreme discharge you can use 80% of the capacity for the rated life! So, with my GC2 setup I can easily use 172 Ahr and not severely affect battery life.
But in general, I like using only 50% of the GC2s capacity, so far my first set gave me 9 good yrs, could have stretched it 10 or possibly 11 but I did notice some degradation in capacity.
Now, my home fridge conversion the fridge typically runs about 1/3 of an hr for each hr, has .9A at 120V draw, with inverter conversion loss right around 10A at 12V..
Or about 3.3Ahr of battery use per hr..
3.3Ahr x 24 hrs = 79.2 Ahrs to run the fridge (although must confess, my inverter has a no load shut down that puts the inverter into a sleep mode that uses very little current when no AC load is present)
Now if I added in inverter no load draw (if I didn't use sleep mode) we would be looking at about 1 Amp draw, but since the inverter would not have a load for 2/3 of hr we get .7 Ahr per hr or about 16 Ahr for 24hrs.
In this case, 79.2 Ahr + 16 Ahr (inverter no load draw)= 95.2 Ahr..
Back to my GC2s, 50% is 107.5 Ahr of capacity - 95.2 Ahr = 12.3 Ahr of safe usable capacity with max battery life..
Now since my setup I amusing inverter with sleep mode I get the following..
107.5 Ahr - 79.2 = 28.3 Ahr of safe usable capacity left over for max battery life..
By the way, everything I have done, has been personally measured, tested and retested. The numbers and times are real, not made up.
If you have a beef with a home fridge conversion it was due to not doing your homework, not a fault of the home fridge.
Done correctly, you can easily run a home fridge conversion off of a pair of GC2s, use lights, water pump, the furnace and throw in some entertainment and be able to go 24 hrs before needing to recharge the batteries.
I do carry a gen, but in reality it is for the times I need to run some AC or fire up the microwave since I don't do week long or weekend boondocking. I typically overnight without power but I am very confidant in my setup that if I were to choose to boondock for a week I would just fire up gen for a couple hrs in morning and evening every day to be able to hang with boondocking a week.
With 300W of solar I could easily reduce gen time to an hr in morning and hr in the evening.
