Solar generator requirements

[Greggo]

I'm researching a recharging solar power generator (large solar/battery) for emergency use and to power the typical daily needs of my 2016 21C (incl the refrig) on electric. House batteries (2 6v) and 180w solar arent powerful enough. My water heater is gas only so that wouldnt be a factor.

Best guess on the typical total electric requirements that I can use to size the right unit? Would a 2000w or 3000w unit do it?

Greg

[John in Santa Cruz]

'solar generator' is a meaningless marketing term for a box of batteries with a solar jack.

I recently upgraded my fridge to a Norcold DC compressor fridge (12V only), and replaced my dual golf cart batts with a pair of SOK Battery 12V 206AH, upgraded the rooftop solar to a 360W monocrystalline (LGE NeonR bought on clearance) Just came back from the first 16 day road trip with this rig, and even when we had hookups, I stayed on solar+battery... It worked *great*. you can read about my upgrades on a thread Li-thiiii-um Continued...

Victron SmartShunt for battery monitoring
Victron SmartSolar MPPT 100/30 solar charge controller
Victron OrionTR DC-DC 12/18 for tow vehicle charging (don't think I really need this, probably could have just disconnected the tow charge)
PD4655LI lithium power converter.

anyways, if I completely disable the solar, our average daily usage is about 20% of the battery capacity, this includes maxxfan, furnace fan, water pump, fridge, and lighting, as well as USB device charging. The solar generated up to 2000 watt*hours per day and would have the batteries fully charged by noon on the typical day where they were charged at sunset, and 90% capacity at dawn.

I did this upgrade incrementally, I initially installed the MPPT connected to the original 160W GoPower solar panel and got 10-15% more power out of it than the original PWM controller.

[Vermilye]

Attempting to run the standard absorption refrigerator on electric while dry camping without a 120V AC power pedestal is not practical. The refrigerator draws around 24 amps continuously on DC, and cycles between 2 - 4 amps on 120V AC. The 12V heater is designed to keep the refrigerator cool while driving, but does not supply enough heat for day to day use.

Over a 24 hour period, on 12V, the refrigerator would use 576 amp hours. Depending on the outside temperatures, how often you open the door, etc, on 120V through an inverter or the "solar battery's" built in inverter it is likely to use at least that much, probably more.

Without an amp hour or watt hour capacity for a "solar battery" it is impossible to tell if a 2000 or 3000 watt version would be large enough. Either would probably be capable of running the refrigerator, but the question is for how long? Unless you have enough solar to supply the full load of the refrigerator, you are going to gradually deplete the battery.

It would take around 500 watts of solar dedicated to the refrigerator alone to keep it running on 120V AC. That is 500 watts input. You would to need to at least double that to meet off angle sun, clouds, etc. Then there is the night time problem. You need to run off the battery for at least 15 hours per day, then find a way to put that energy back into the battery during the time the sun is available. Since you will be using all of the 1000 watts to power the refrigerator, you will need at least another 1000 watts or more to refill the battery. There is not enough room on the roof of a 21 for 2000+ watts of solar panels, and that many portables would be tough to carry & set up and down.

It isn't impossible, but impractical. A better solution is to run a absorption refrigerator on propane when camping without an electrical hookup, or switch to a 12V DC compressor refrigerator with a efficient compressor that draws around 3-6 amps 50% of the time.

[Greggo]

Thanks Jon. My electrical knowledge is limited to knowing which batteries to put in a flashlight.

I'll have a look at a compressor refrig. I bought a small Engel portable a few years ago. Runs forever on 12v.

[John in Santa Cruz]

If you have a RMD8555, then the Norcold N2175 is an exact fit. 12V only, very power efficient.

[Greggo]

great! Ill get.one ordered. Mods dont usually go that easy.

G

[John in Santa Cruz]

btw, the Norcold N2175 is shipped as a righthand hinge (door opens on the left side), while the RMD8555 fridge that came in my 21C was lefthand hinge. It turns out you can reverse the Norcold door without any new parts (details are in the Installation manual), but my wife decided she preferred the left-side opening door as she can stage stuff on the dinette table on the 21C. If she likes it like that, I do too! and the pullout freezer on the bottom is really sweet.