Run a refrigerator off solar

[someguy]

I’m using a apt. Fridge and want to know if my batteries will be enough. The fridge is 115v 2.5/6 amps (run/start up) I have 600w in solar panels 360AH in batteries using a 3000 watt pure sine inverter. Then I have a laptop I charge and phones that use the rest of the power.
I’m thinking if I use the generator to start the fridge then I should be able to run the fridge on solar all day since it doesn’t need to run 24/7. Also I’m in the desert so sun isn’t and issue.
How do I do the math to find out how much AH’s I need.

[rossvtaylor]

Multiply the voltage by the amperage (current) draw... so 120Vx2.5 = 300...so the fridge draws about 300 Watts when running. How many hours a day will it run? Lets say, maybe in a bad case, 25% of the time...so 6 hours a day. 300W/12V=25 amps, times 6 is 150Ah. I think this is more than it would actually run, but you ought to test it. Get a Kill A Watt meter and plug in your fridge, to measure it for a few days. That will give you the most accurate usage.

Now, will your system run that? As to start up, sure. Your 3000W inverter is more than enough and the starting current draw is brief, so I left it out of the calculations...we're close enough. As to day-to-day demands, we'd need more information. To start with, what kind of batteries do you have? 360Ah in FLA (regular lead acid) batteries gives you about 180Ah of usable energy. Lithiums will yield more.

[someguy]

Thanks Ross,
So I have 4-90Ah agm batteries
I did some more research before your comment and came up with 7.5 hours of run time. Almost the same as what you had.

[rossvtaylor]

Originally Posted by someguy

Thanks Ross,
So I have 4-90Ah agm batteries
I did some more research before your comment and came up with 7.5 hours of run time. Almost the same as what you had.

Yay, I did math! I can go drink wine now...

We have an almost identical setup, with the exception of more solar (1100W) on an ambulance conversion rig and the fridge has been "on" in there for 4 years without issue. We don't even bother to turn it off when we're not using the rig.