# mini fridge off grid what inverter and battery choice



## wittey (Nov 17, 2003)

I have a Mini fridge/freezer that I would like to use at my cabin. I would like to run on Batteries.
Here is what i have
Refrigerator 115v .89 amps =102 whats
I have a 3800 Watt generator to charge batteries.


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## ShannonR (Nov 28, 2012)

First, what kind of batteries?
Are you using solar or something besides the generator to charge your batteries? If not, I suspect you'll be running your generator a lot

A mini fridge wasn't quite a go with my 1150watt solar setup, I still had to turn it [email protected] night so it wouldn't drain my (pair of golf cart) batteries. Went back to the propane refrigerator. And mine only drew 40watts, or so the tag on it said. The constant cycling on and off was a huge wear on both my batteries and my little RV inverter. If I had to try this again I would buy something made to run on either 12v power or something specifically for solar.

Just my personal experience.


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## wittey (Nov 17, 2003)

Not sure of the battery until someone suggests one. I only have 2 - 40 watt solar panels but was not planning to use them. don't know if i could us them as maybe as a trickle charge. This is in Northern AZ. Thought maybe i could use the fridge for when I am there for more than 3-5 days as i would need haul a lot of ice and then go back into town and thats 3 hours round trip, it takes me 40 minutes the last mile to my property. i would probably run the generator a couple times a day to charge the batteries.


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## Lisa in WA (Oct 11, 2004)

We used a propane fridge for the first several years off grid till we had a big enough power system and then used a super efficient electric fridge.


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## ShannonR (Nov 28, 2012)

How much money are you willing to spend on batteries, inverter, ect. ? And are you wanting to run JUST a refrigerator, or other things too?

L-16 s are good but come in 6volts and cost a few hundred each, you would need to buy a minimum of two. Four would be better. Plus the wiring to hook them in series, and wiring to your inverter. You would also need a battery charger that isn't made for cars and that wont hurt your batteries...found this out the hard way with an old car batt charger.

A cheap bottom of the line 12v inverter will cost you another $100 or so. If you want to add your solar panels to this mix (yes, you can do that) you'll need the wiring and a charge controller for those as well.

So, really it doesn't make much economical sense for the low usage you plan on getting out of your potential system, IMO. I still say 12v or proane fridge would be better. I bought mine used for $75, a propane version of the mini fridge you want to run. For just a few days at a time the propane cost is low, I think I spend about $25 per month on propane for my fridge, propane on demand shower, and stove. That is for living offgrid full time.


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## wittey (Nov 17, 2003)

the fridge is all for now. since I already have it. I generally use it in motels when i am on the road working. I it would save me taking 4 or 5 extra coolers of ice to my property.


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## ShannonR (Nov 28, 2012)

Ice is certainly no fun...been there, done that. But in this situation I am not sure that part time use of an electric refrig out at your property would be too economical.

I would say that, at the very least a pair of golf cart batteries would be needed to run the generator just a couple times per day and keep that energy sucker running. My golf cart batteries cost me around $220 each, fairly affordable. Again, these are 6v battties and you would need two. And the inverter, $100 or so. Appropriate wiring, maybe $30. Then a battery charger if you don't have one already, this is all bare bones equipment for what you want to do. 
You do have a generator already, or no? Generator gas, for the time you would need to be recharging your batteries, adds up quick.

To me, that is a lot of $$ to be able to run a small refrig just "because you already have it". How many new mini fridges could you buy with the money you want to put into making it work at this one spot, and part time at that?


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## wy_white_wolf (Oct 14, 2004)

Since the refrigerators compressor does not run all the time you should to get a kill-a-watt meter and record the usage for at least 1 week under normal usage to properly size the solar panel and battery.

That said they are typically about 25 to 50% run time. so:

102 watts*24 hours*50% = 1224 watthours consumed in a day.

One should only use 20% of the battery bank in a day. That will also give you 2.5 days atomony before reaching the never go below mark of 50% battery capacity.

1224WH/20%=6120wWH battery capacity or
510AH at 12VDC or
255AH at 24VDC

For an inverter you'll want a pure sine wave one of at least 4 times the load to insure it can handle the start up load. So at least 400 watts. Don't want to go too large as it would then waste to much power.

Solar panels if you decide to add would be calculated by:

daily watt hour requirement *1.5 / minimum monthly sun hour average for a PWM controller or
daily watt hour requirement *1.2 / minimum monthly sun hour average for a MPPT controller

With off-grid you need to calculate for the worst case scenario so you can't use yearly average for sun hours (insolation).

I find that small solar off-grid systems usually run about $2k to $2.5k for each kilowatt needed daily so this should run about $2.5k to $3k using quality components.

WWW


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## wittey (Nov 17, 2003)

"I have a 3800 Watt generator to charge batteries" it's gas and propane.


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## wy_white_wolf (Oct 14, 2004)

wittey said:


> "I have a 3800 Watt generator to charge batteries" it's gas and propane.


 That's why I put "if you decide to add" on the PV part. Doesn't change anything on the battery or inverter needed.

WWW


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## wittey (Nov 17, 2003)

Thanks Wolf. Bought the kill-a-watt meter and hooked it up yesterday.


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## wittey (Nov 17, 2003)

1224WH/20%=6120wWH battery capacity or
510AH at 12VDC or
255AH at 24VDC

Would that mean 4 golf cart batteries(T-105)?


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## wy_white_wolf (Oct 14, 2004)

wittey said:


> 1224WH/20%=6120wWH battery capacity or
> 510AH at 12VDC or
> 255AH at 24VDC
> 
> Would that mean 4 golf cart batteries(T-105)?


 T-105s are @225AH at 6V. So 4 of them would be 225AH at 24V when wired in series or 450AH @12V when wired 2 series I parrallel. A little smaller than my numbers but mine are just a SWAG.

Once you get the usage over a week or so from the kill-a-watt you'll be able to calculate a better numbers and then know if T-105s are big enough.

WWW


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## wittey (Nov 17, 2003)

wy_white_wolf said:


> T-105s are @225AH at 6V. So 4 of them would be 225AH at 24V when wired in series or 450AH @12V when wired 2 series I parrallel. A little smaller than my numbers but mine are just a SWAG.
> 
> Once you get the usage over a week or so from the kill-a-watt you'll be able to calculate a better numbers and then know if T-105s are big enough.
> 
> WWW


1 week and 1 hour and 15mins usage 7.23


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## wy_white_wolf (Oct 14, 2004)

wittey said:


> 1 week and 1 hour and 15mins usage 7.23


 7023WH/169.25H*24H = 1025WH daily

Just a little less than I guessed.

1025 / 20% = 5125WH battery bank
427AH @12V
213AH @ 24V

2 L16s would be my choice for 12VDC
4 T-105s would work for 24VDC

Both those allow a single string without having to parallel batteries.

There should have also been a readout for max amp or wattage draw. That would determine the minimum size for you inverter.

WWW


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## wittey (Nov 17, 2003)

wy_white_wolf said:


> 7023WH/169.25H*24H = 1025WH daily
> 
> Just a little less than I guessed.
> 
> ...


1 week and 16 hrs,(183hrs) 7.87 kwh, 122 volts


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## Earthworm77 (Jan 18, 2016)

ShannonR said:


> First, what kind of batteries?
> Are you using solar or something besides the generator to charge your batteries? If not, I suspect you'll be running your generator a lot
> 
> A mini fridge wasn't quite a go with my 1150watt solar setup, I still had to turn it [email protected] night so it wouldn't drain my (pair of golf cart) batteries. Went back to the propane refrigerator. And mine only drew 40watts, or so the tag on it said. The constant cycling on and off was a huge wear on both my batteries and my little RV inverter. If I had to try this again I would buy something made to run on either 12v power or something specifically for solar.
> ...



Shannon your system with 1150watts should be able to handle a mini fridge, the reason it likely didn't was that your (2) 6 volt batteries are not enough to run it around the clock......the solution is a larger battery bank, I'd start with 2 12volt 125AH batteries.


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## TnAndy (Sep 15, 2005)

Earthworm77 said:


> Shannon your system with 1150watts should be able to handle a mini fridge, the reason it likely didn't was that your (2) 6 volt batteries are not enough to run it around the clock......the solution is a larger battery bank, I'd start with 2 12volt 125AH batteries.



I'd agree. 

I set up a 1500w system for a friend's off grid cabin, and he runs a smaller, full size (energy star rated) fridge, along with lights, a pressure pump (has rain water collection for his water), general purpose outlets, etc. But we put in a bank of 8 L-16 (two strings of 4...6v, 350a/hr each....24v system), 700a/hr total.

Backup generator runs very little.

Side note:

Lot of times if you look at mini-fridge ratings, they aren't all that great....opposite of what you'd think for the size of them. I'd guess they are simply built cheaper (less insulation, etc), hitting more for the low initial cost market over energy use. Go to the Dept of Energy website and see if you can find yours......you 'might' be better off with a regular fridge !


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## AmericanStand (Jul 29, 2014)

I've seen a solar ice maker. That uses salt and ammonia I think. 
It will make about 8 pounds of ice per charge. Sometimes twice a day. 
That might be a cheaper way to go.


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## Fire-Man (Apr 30, 2005)

Just for Info---I went to Walmarts and bought a 7cf freezer and used a thermostat I took out of a old fridge---The freezer stayed between 36 and 42 degree's(no Ice) drawed about 300 watts per day. Room temp got up to high 80's...tested for a few weeks, but not during the hottest part of summer.

Just seen the post about ice-----but I will still leave this post up just for info.


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## DanBond (Nov 25, 2020)

Thank you for your advice


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## johndensmore24 (Jan 12, 2021)

This primarily depends on what kind of batteries you have. Maybe you're talking about big batteries. I doubt that you can take enough batteries on your boat, such as AAAA, with which you can maintain your freezer. In any case, it is not very efficient and quite expensive. I think the guys from thetoolscout.com they will be able to help you with advice, since the option of replacing the batteries every cruise is not very good. Personally, I think that the best way to cope with this is a battery with a large volume.


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