A blanket question, but on average those with residential fridges, how long will can it run on a single 12V deep cell battery? I know there are variables here, size of battery, parasitic draws etc..but looking for just a generalized run time.

Hours; maybe 12ish hours on average, if there is such a thing as average.This is a question that can be answered pretty well, at least well enough for back-of-the-envelope calculations, by comparing the usable energy storage of the battery with the energy consumption of a residential fridge. According to the Energy Star labels I've seen, a typical not huge fridge use around 1 kWh or a bit more per day on average (under their test conditions). A single marine/RV battery has maybe 50 Ah of usable charge, which multiplied by 12V yields 600 Wh or 0.6 kWh of energy.

Resi's have an initial startup surge, which I'm not sure a single battery will handle.

If you are going residential fridge then do it properly...four 6 volt batteries and adequate solar. Set yourself up for success, not failure.

DrewE wrote:Hours; maybe 12ish hours on average, if there is such a thing as average.This is a question that can be answered pretty well, at least well enough for back-of-the-envelope calculations, by comparing the usable energy storage of the battery with the energy consumption of a residential fridge. According to the Energy Star labels I've seen, a typical not huge fridge use around 1 kWh or a bit more per day on average (under their test conditions). A single marine/RV battery has maybe 50 Ah of usable charge, which multiplied by 12V yields 600 Wh or 0.6 kWh of energy.Well, except that (a) the usual battery on an RV is rated 75 or 80 AH, so the usable is more like 37.5 or 40 AH, and (b) that rating assumes a 20 hour discharge time, and will be less with a shorter discharge time, so that you are not going to get those 12 hours. Probably more like 8 or 9. Into the bargain, the compressor startup surge (as @oldman pointed out) will likely be beyond the single battery to supply; too many amps drawn at once.

I'm also looking at a model with a residential refrigerator. Drew: When you say 12 hours average does that consider only drawing the battery to about half charged? I've read that you should not go below half charge on the ordinary RV batteries. naturist: Would 2 12V batteries probably handle the startup surge?

Rez fridge question | Good Sam Community

40 Replies

time2roll
Nomad
Feb 20, 2020
Generally you should have two batteries minimum. Lunch stop is fine.
Overnight will work them hard so don't expect to run to much else.

For extended off-grid camping 4 to 6+ batteries would no be unreasonable.
Gdetrailer
Explorer III
Feb 20, 2020
Boon Docker wrote:
JimK-NY wrote:
Boon Docker wrote:
JimK-NY

A 70 ah battery will last a lot longer than 3 1/2 hours unless the fridge is running continually non stop, which would only happen if the fridge door was left wide open the whole time

Which residential refrigerator do you have that is using so little power?

What I am trying to say is a fridge does not run constantly at 10 amps for 3 1/2 hrs non stop. So a 70 ah battery would last longer than 3 1/2 hrs.

Fridge may not run 3 1/2 non stop, however there IS lots of OTHER parasitic items which DO.

RV stereo, rv heater, DSI water heater, propane detector all draw small amounts of power even when turned off..

Heck even a 16K BTU furnace will draw 7.5A while the fan motor is turning, jump to a 30K BTU furnace and now you find yourself drawing 10A with the fan turning....

Turn them on, use some lights and perhaps water pump and now suddenly you now have a near flat 70ahr battery in short order..

A single 70Ahr battery is not going to support the startup surge of the fridge once the battery has a few Ahrs drawn out. The battery voltage will sag more and more under the surge until the inverter drops out at around 10.5-11V..

Not much leeway with 12V systems from full resting voltage 12.8V to a dead flat of 10.5 V with most inverters alarming at 11V or shutting down around 10.5V.
smarty
Explorer II
Feb 18, 2020
temperature outdoors greatly impacts this calculation as well, if it is 95 degrees out...
austinjenna
Explorer
Feb 18, 2020
Thanks wowens79. The only other foreseeable problem I can see is when we overnight somewhere while travelling and dont have hookups. I guess 4 golf cart batteries wired in series & parallel might do it for an overnight trip.
wowens79
Explorer III
Feb 18, 2020
Sounds like my situation is like yours, I store my camper at a storage place without power, and will pick up the camper on the way home to load it up.

No need to pre-chill it. Takes about 20-30 min to cool off, and if the items you load into it are already refrigerated it stays cold. We towed 14 hours with 2 6v golf cart batteries with the charge from the truck, and still had plenty of battery power.

When I go to get the camper, I turn on the inverter/fridge, and the hookup the camper, and drive the 10 min to the house, by the time I’m ready to load it, it’s pretty chilly in the freezer and cool in the fridge.

I’ve had a resi fridge for over 3 years, and I would not go back. We are in Georgia, and not really places to boon dock, so we always have power at our destination. If you camp with hookups go resi.
Walaby
Explorer II
Feb 18, 2020
Doesn't the TV contribute to charging the batteries while towing? I know it won't necessarily keep up totally, but certainly it should contribute to the amount of time you can go between recharge time, right?

Mike
Boon_Docker
Explorer III
Feb 18, 2020
JimK-NY wrote:
Boon Docker wrote:
JimK-NY

A 70 ah battery will last a lot longer than 3 1/2 hours unless the fridge is running continually non stop, which would only happen if the fridge door was left wide open the whole time

Which residential refrigerator do you have that is using so little power?

What I am trying to say is a fridge does not run constantly at 10 amps for 3 1/2 hrs non stop. So a 70 ah battery would last longer than 3 1/2 hrs.
AllegroD
Nomad
Feb 17, 2020
2013 tiffin 36LA, Samasung RF18HFENBSR, 2 6v GC2, 230AH.

with batteries at 12.7 I can get 10 hours out of them if I run nothing else but the parasitics and outside temp 70-85. That leaves the batts at 12.0-12.1.
JimK-NY
Explorer II
Feb 17, 2020
Boon Docker wrote:
JimK-NY

A 70 ah battery will last a lot longer than 3 1/2 hours unless the fridge is running continually non stop, which would only happen if the fridge door was left wide open the whole time

Which residential refrigerator do you have that is using so little power?
Boon_Docker
Explorer III
Feb 17, 2020
JimK-NY

A 70 ah battery will last a lot longer than 3 1/2 hours unless the fridge is running continually non stop, which would only happen if the fridge door was left wide open the whole time