Running Norcold Refrigerator on Solar Power Only

[The Loonies]

We have to leave our camper for 7 days in Southern CA  where there is endless sun.

Has anyone run the refrigerator strictly on solar for that length of time? There will be no other energy draw as it will be empty.

We have 3 Lithionic Batteries 400 AH, 340 Watt Solar Panels.

Trying not to use propane if possible.  We realize it is the most efficient way, but we are interested in testing the limits of our solar package 

 

[Mike and Carol]

I don’t know the answer but I would rather test my batteries when I could be present, at least some of the time.  It does get cloudy in Southern CA from time to time, I’d check the forecast!  The fridge uses very little propane but can drain batteries in the right circumstances.  Good luck!  Mike

[Steph and Dud B]

I assume you mean running the 3-way fridge on 12 volts, and you have the 390Ah lithium package? You can't use the last 10% (39 Ah) from your batteries due to the low voltage shutdown, so you have 351 Ah available.

We have the larger 640 Ah package. When traveling in rainy weather (no solar charging) with the 3-way Norcold fridge running on 12v, we consume approx. 4% of our state of charge per hour on warm days. Based on that, I'd assume you'd use about 7% of your SOC power per hour in the same circumstances (because of your smaller battery bank).

Mid-summer SoCal gets about 14 hours of daylight, so that leaves 8 hours of minimal or no charging. 8x7 would guestimate a SOC loss of 56%/day (assuming perfect sunny weather). That's about 219 of your 351 Ah.

Your solar panels theoretically generate 340 watts, or about 24 amps, but that's only in a lab environment. Let's say you can actually get about half that real-world. 12 amps averaged over the 14 hours of daylight. That would replace 168 of the 219 used. So, best case, you're losing over 51 amps a day. Too much. I don't think you'll make it, and you could permanently damage your lithium batteries. (Maybe someone with better solar knowledge can jump in here.)

OTOH, 2 full propane tanks will easily run your fridge for weeks with the small amount of electricity used for the fridge control board easily replaced by solar. I'd fill my propane tanks, put the regulator on auto switchover, and leave it be.

[MAX Burner]

4 minutes ago, Steph and Dud B said:

I'd fill my propane tanks, put the regulator on auto switchover, and leave it be.

Concur, 100%.  The only time we select the 12v mode on the fridge is when towing.  As we're setting up at the end of a haul, a key element of the checklist is to set the fridge into the gas mode - and it stays there until the next departure.

[The Loonies]

Thank you all....great info from Steph and Dud B. 

[SeaDawg]

@The Loonies, I would not expect a 3way, on dc, to keep up, for a week. I think your batteries could deplete by day 5 or 6. 340 watts of solar doesn't  "cover" the use of dc on a 3way.

Much higher than a dc compressor fridge.

If I were you, I'd clean out the fridge, turn it off, and sleep easy. 

[MobileJoy]

I also have the 390Ah Lithionics and 340w solar system. This week I took Mojo out of storage. Batteries were at 100% because I keep them charged. Since it was time to do a full discharge cycle, I turned on the Norcold fridge on DC mode. The fridge was not pre-cooled, and the temperature inside Mojo was 60 degrees. Solar conditions were not good. The batteries entered LBCO in just under 1 day. In addition, I had the heater running (set at 65 degrees) so the blower was also operating, as was the Xantrex inverter. Not an apples-to-apples comparison with your situation.

Usually, I use DC mode only when traveling, and I observe 5-10% drain from fully charged batteries depending on trip duration, outside temperature, and sun exposure. I haven't tried to gauge this accurately.

Regarding low battery cutoff, this is done individually as each battery reaches 12.1V. When there is power draw, voltage tends to be lower, so the batteries can cut off before they get down to 10% of charge. In this case, the batteries did cut off at about 13% of charge.

[MAX Burner]

That's a very helpful report, @MobileJoy - thanks for sharing that data.  It matches very closely to our DC consumption profile.   We're currently staying in northern NM near Taos where "after sunset temps" dip to mid-20's overnight.  Not using available shore shorepower, we're running the furnace, fridge, and WH continuously at night off our BB battery bank.  Checking street side compartment temp (our coldest, excluding the "Garage") read 52F at 0330.  Daytime temps are in the balmy mid-50's.  This is what we call, "3rd Season Camping" - cold but not in the single digit realm. 

FYI:  Our SOC last night before hitting the rack was 92% after a full day of rather low sun angle shine and wall-to-wall sun (no clouds) - pulling a MAX of 185w from the 340w available modules mounted flat up top.  This morning, at coffee/Kahlua time, our SOC started at 62% - not bad considering 3 major systems running all night.  It's 0740 now (an hour later), and with early sun - the SOC is now 68%.  With these conditions, I expect to return to Casablanca this PM and discover very close to 100% SOC.

More backcountry skiing with the 2 Knuckleheads - will provide SITREP afterwards...

Cheers, ALL!