Hi, hope I posted in the correct category.We have a new Allegro (very nice) with residential fridge. We sometimes want to park it in storage for a few days between trips. I would like to have enough solar to keep the fridge on an power the various little things that drain the batteries. We live in Southern California, so solar works well.Can you suggest solar panel size that we need? Also, are there brands to prefer / avoid?

Hi,Start with an energy audit.Here is some reading for you to do: https://freecampsites.net/adding-solar/

i have a residential fridge in the safariwith 600+ watts for solar and 665 ampHr battery bank,5 BIG AGM batteriesjust fridge , no lights etc, with good sunny weatheri still loose approx 4-5% per day, sitting still stored, with fridge onexample fully charged 100% at 6PM tonighttomorrow night at 6pm my meter will indicate 95%, the next day 90% the next 6pm 85% thats approx 35 ampHrs per day loss, that is NOW, more power is produced during the summeri would suggest a minimum of 400w of solarhow many batteries, what type, what sizethe OEM battery setup should be good for at least 24hrs, with out any solar

If the fridge uses 7 amps DC via inverter, and runs 16 hrs a day being "on" then that is 112 AH from the batteries per 24 hrs.To keep up with that, with 7 hours of good sunshine per day, you will need a steady 16 amps from the solar for that 7 hours. You would need about 300w of panels lying flat. It doesn't work like that of course because the sun rises and falls during that 7 hours.So perhaps make it 500w. Two 250w panels and a 20 or 30 amp MPPT controller to run them.But--since the sun does not shine like that every day, you need enough battery bank to carry you through until the sun shines again. How much battery is that? "It depends."

Not just enough panels....enough battery amp hours...building a system just for the days you are home and not plugged in? Hmmm. Not what I’d do...did. Learn solar basics before buying anything.

BFL13,Most scenarios use 5 hours of production per day, not 7.

Solar to keep fridge running | Good Sam Community

30 Replies

valhalla360
Navigator
Dec 05, 2017
DrewE wrote:
valhalla360 wrote:
So what is the draw when the compressor is running and what percentage of the day is the compressor running.

Until we have a fair estimate for that, any numbers being thrown around are wild guesses that may or may not work.

Let's run some sample numbers and you can update based on your real life numbers:
- Assume 3amps at 120v when the compressor is running
- Assume 50% duty cycle

I realize this wasn't intended to be realistic, but it's worth noting that modern fridges do not use anywhere near 3A running. (Starting power is a different matter altogether.) A not unreasonable rough estimate, lacking any better data, might be around 1 kWh per day or so for an ordinary sized, fairly basic residential fridge. Often the dorm sized fridges do not use very much less energy, despite being much smaller.

An absorption fridge running on AC power uses significantly more energy, maybe around 3-4 kWh per day.

While there are high efficiency models that do better, 3 amps isn't really out of the ordinary. You would think an RV manufacturer would be aware of this but if they are just shoving in the cheapest model that will fit, it could easily be this high.

Also, if the OP will be storing it on a sunny 90 degree day with the air/con off, the duty cycle might be upwards of 75-90% because your average RV acts like a solar oven. (a lot of this comes down to how well insulated the fridge is)

But again, the OP needs to get the numbers off his fridge. Anyone telling him 600w is what he needs is just making a wild guess that could be way too low resulting in the OP wasting a lot of money on a system that doesn't serve his needs.
time2roll
Nomad
Dec 05, 2017
I think every RV should have 600 watts solar. Anything less is unreasonable ;)

Every home should also have 1 watt solar per square foot of space too.
SoundGuy
Explorer
Dec 04, 2017
Bill.Satellite wrote:
It really doesn't matter what we think he should or should not do as it has nothing to do with the topic ...

SoundGuy wrote:
Sure it does, as the OP in his most recent post said - "I just want to know if there is a reasonable way to leave my (compressor) fridge on for a few days while in storage." Answer - solar is not the answer because of the size (i.e. cost) that would be required.

Bill.Satellite wrote:
"Not the answer" is your opinion and not the answer.

The OP asked for a reasonable way to leave his compressor fridge running for a few days while in storage. 400, 500, 600 watts of solar or more is hardly "reasonable" for the sole purpose of running a fridge while in storage, particularly when solar efficiency is so weather dependent. :R

And of course this is "my opinion", just as everything posted on these forums is someone's "opinion". :S
Bill_Satellite
Explorer II
Dec 04, 2017
SoundGuy wrote:
Bill.Satellite wrote:
It really doesn't matter what we think he should or should not do as it has nothing to do with the topic ...

Sure it does, as the OP in his most recent post said - "I just want to know if there is a reasonable way to leave my (compressor) fridge on for a few days while in storage." Answer - solar is not the answer because of the size (i.e. cost) that would be required.

"Not the answer" is your opinion and not the answer. Only the OP can make a choice and answer his own question. Maybe he would prefer an Earth friendly, owner friendly solution and not be as concerned about the cost as you are.
Will a solar installation work? You bet it will.
turbojimmy
Explorer
Dec 04, 2017
BFL13 wrote:
Whatever, the OP's plan is probably too optimistic in real life. I have posted more than a few times that if you ever go off- grid, you better have a fridge than can run on propane. Learned that the hard way! BTDT etc. :(

Yeah that was my initial thought. Whatever the answer is, it's not going to be practical for the OP's intended use. It's going to take a lot of panels, wiring and batteries.
MrWizard
Moderator
Dec 04, 2017
The point i was making
Is the batteries and solar will carry the fridge for several days 4-5
Before additional recharge is absolutely needed
But that it does not completely cover fridge power even in storage mode
And the OP said several days, not two , not overnight
I'm thinking he means 4-5 days
pianotuna
Nomad III
Dec 04, 2017
Hi,

Both MrWizard and I have used 12 volt telecom AGM. They weigh 105 lbs and are a "surplus acid" design which puts them somewhere between flooded and regular AGM jars. Mine are 139 amp-hours each.

theoldwizard1 wrote:
MrWizard wrote:
i have a residential fridge in the safari
with 600+ watts for solar and 665 ampHr battery bank,
5 BIG AGM batteries

Curious, what brand and model AGM batteries ?
BFL13
Explorer II
Dec 04, 2017
The 3.2 cuft 120v only fridge we had in the truck camper running on inverter ( with good wiring) pulled 4 amps when running. Replaced with 3.6ish cuft DM700L absorption fridge. On same inverter set-up it pulls 14 amps when running on 120v. (It runs on propane off-grid!)
DrewE
Explorer II
Dec 04, 2017
valhalla360 wrote:
So what is the draw when the compressor is running and what percentage of the day is the compressor running.

Until we have a fair estimate for that, any numbers being thrown around are wild guesses that may or may not work.

Let's run some sample numbers and you can update based on your real life numbers:
- Assume 3amps at 120v when the compressor is running
- Assume 50% duty cycle

I realize this wasn't intended to be realistic, but it's worth noting that modern fridges do not use anywhere near 3A running. (Starting power is a different matter altogether.) A not unreasonable rough estimate, lacking any better data, might be around 1 kWh per day or so for an ordinary sized, fairly basic residential fridge. Often the dorm sized fridges do not use very much less energy, despite being much smaller.

An absorption fridge running on AC power uses significantly more energy, maybe around 3-4 kWh per day.
red31
Explorer
Dec 04, 2017
Winnipeg wrote:
Do I appear silly to want to protect my $20 worth of condiments with an expensive upgrade. Guilty, if you like. The RV lifestyle is not about frugal financial decisions.

I just want to know if there is a reasonable way to leave my fridge on for a few days while in storage. Obviously there are other benefits to adding solar (dry camping, glogal warming, etc.), but I didn't see the need to make a complete case for it.

That seems to answer the question well, hell yes!

Use the info in this tread as a guide and measure your storage energy needs. Keep in mind that LA gets 1/2 the solar in winter than summer on flat panels. Design for winter? spring? Decide to go hog wild or just supplement auto generator use.