Residential fridge battery usage

[Lilwilly]

I realize this is a very subjective question, but I’m trying to find out how long a residential fridge in a newer 36Z - 4 house batteries, 450 watts solar, and 2K watt inverter - will run before the batteries need to be charged?

Any information is greatly appreciated!

[DavidM]

I assume you are talking about a true 120V AC powered residential fridge and not a 12V DC compressor fridge.

Size makes a difference, but a moderate size 12 cu ft residential fridge should consume roughly 100 amp hours of 12V DC in 24 hours.

Let's assume your 4 house batteries are 100 amp hours each. Your 450 watts of solar wil put out 100-150 amp hours daily in average summer sun.

So your solar panels should barely keep up if that is the only load but it isn't. Lights, water pump, fans, device charging, etc. all adds up to maybe another 25 amp hours daily.

But as a worst, worst case, you have a 175 Ah demand and a 100 Ah solar supply so you are short 75 Ahs which your 400 Ah standard, not Lithium should be able to cover for 2-3 days before going below 50%. As a best, best case you have a 125 Ah demand and your solar puts out and average of 150 Ah. In this case you can go forever.

This of course assumes you are camping in the sun.

David

[creativepart]

I find real world solar - though I have only 300w -- doesn't add as much as it seems on paper.

I have a large 3-door residential fridge, 400 ah of AGM batteries, a 2000w inverter. Over night my fridge consumes 30% of my total battery storage. And that is with NOTHING else consuming electricity, just testing in the driveway. I started the test at sundown.

The following day the solar starts to help out but any clouds can frustrate this process. And I don't quite break even so I lose another 10% of my batteries between sun up and darkness. So, now I'm close to 60% SOC as the night starts. Then it's minus another 30% over night and now I'm down to a 30% SOC or FAR too much discharged from my batteries.

I wouldn't plan on more than 24hrs and certainly doubt you'll make it two days.

Do a test in your driveway if you want to have a better feel for this.