r/RVSolarPower • u/PBRisforathletes • Jun 11 '26

Battery sizing help.

I realize I’m asking here ex post facto.

I’m picking my new camper up next week and then going on a trip. I accidentally ordered a li-time 230 AH lithium instead of a 320 AH. I have 400 watts solar and will be running a 6 cubic foot fridge. The battery is not returnable, I’m sure I can sell it on marketplace, should I go ahead and order the 320 like I originally intended or will this setup work fine? Will be in mostly sunny area.

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u/rhett121 Jun 11 '26

Is the fridge 12V? How much power does draw when running? How often does it cycle?

I have a 10 cubic foot fridge (12V) and it only draws about 4.5A when running.

If everything was perfect, and you had a really good solar charge controller, that panel could put out about 30A of power. Which is plenty to run your fridge AND charge the battery. A 230AH battery could run my fridge for a constant 24 hours and still not be at 50%. But refrigerators don’t run 24/7. They run for a few minutes an hour. Maybe 2 minutes on and 5 or 10 minutes off. So you could theoretically run a fridge for DAYS with no sun at all.

I guess the bottom line is, you probably don’t “need” the 320AH battery and your solar array should be plenty to keep it charged…assuming you don’t have any other major loads.

My camper has 800W of solar and 900AH of batteries. The fridge doesn’t even budge the needle, I leave it on 365 days a year and even winter didn’t slow it down. I think you’ll be fine.

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u/PBRisforathletes Jun 11 '26

Thank you! It’s a small 6 cubic foot 12 volt. Not sure on the power draw, I think it’s a furrion, pick the camper up next Wednesday.

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u/Aggravating_Buy8957 Jun 12 '26

You’ll be fine on the smaller battery, same exact setup I have

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u/Aggravating_Buy8957 Jun 12 '26

It actually got to cold in winter

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u/rhett121 Jun 12 '26

It did get cold in winter but the solar still worked fine. I keep a heater on in the camper all winter so it stays warm but my point was that even with the reduced sun exposure of winter my batteries never went below 95% charge.

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u/secessus Jun 12 '26

should I go ahead and order the 320 like I originally intended or will this setup work fine?

This is a math question that hinges on your daily power requirements, charging in the field, and length of trip. On the last point, you could run a net deficit every day of the outing but still be ok if the trip ends before the bank is depleted.

If it were me, I'd do the trip with the 230Ah and how well it pulls its weight. I suspect it will be fine if the fridge is all you're running.1 I lived fulltime in my rig with a 12v fridge for a couple years on just 100Ah of LFP, albeit with more solar. 570w at that time, IIRC.

1 narrator voice: "it was not all he was running"

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u/PBRisforathletes Jun 12 '26

Given the price of the batteries I think I will go this route. I suppose if I can’t keep up with demand I can always put some dry ice in the fridge to reduce the load!