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Click here for the Grey Nomads website -> The Grey Nomads Forum -> Solar Power -> Size of solar panel required to run an average 40 lt 12 volt fridge/freezer?
Post Info TOPIC: Size of solar panel required to run an average 40 lt 12 volt fridge/freezer?
Bicyclecamper


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Size of solar panel required to run an average 40 lt 12 volt fridge/freezer?
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 I haven't got the F/F yet, but it will be about 40 lts. I have heard that a solar panel on it's own  can run a  fridge during the day depending on amps per hour required to run fridge, so is it possible just to use a solar panel on it's own to power a fridge during the day?. I have  a Finch 3 way 41 lt to use instead , if this is  not possible to do on a 2 way fridge. I will also have an 100ah battery for the night, just hoping a suitable s/panel will run  the fridge during the day. 



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Peter_n_Margaret


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What electrical specifications do you have for the fridge?
Cheers,
Peter

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OKA196, 4x4 'C' Class, DIY, self contained motorhome. 960W of solar, 400Ah of AGMs, 310L water, 280L fuel. https://www.oka4wd.com/forum/members-vehicles-public/569-oka196-xt-motorhome
 

 
Whenarewethere


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If you download the manual for Waeco or Engel etc. It gives the ratings of the fridge. A 40L fridge is not a lot more to my 28L fridge.

The problem with running a fridge directly from a solar panel is everytime a cloud goes over or a very small shadow over the panel the solar panel effectively produces nothing.

The fridge will cycle off for a few minutes before restarting so the compressor lives longer.

The other issue is the solar panel's voltage is around 18 volts, you will kill your fridge. Which will cost you more than a controller & battery!

You need a solar panel, controller, battery & thick enough wire to minimise resistance.

If your fridge is packed full, as it should be to maintain maximum thermal mass, leave it off at night & cover it with a doona or sleeping bag. It will be ok in the morning. We have done this.

 

Ways to reduce fridge energy consumption:

https://thegreynomads.activeboard.com/t65059593/extra-fridge-insulation-wattage-test/



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50L custom fuel rack 6x20W 100/20mppt 4x26Ah gel 28L super insulated fridge TPMS 3 ARB compressors heatsink fan cooled 4L tank aftercooler Air/water OCD cleaning 4 stage car acoustic insulation.
Peter_n_Margaret


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"Direct from the solar panel" is a misnomer. It can not happen (unless it is specifically designed to do so, which it is not).
But it can run from the load terminals of the solar controller of from the battery which is charged by the solar panel and solar controller.
We need the fridge electrical specifications to provide decent advise.
Cheers,
Peter

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OKA196, 4x4 'C' Class, DIY, self contained motorhome. 960W of solar, 400Ah of AGMs, 310L water, 280L fuel. https://www.oka4wd.com/forum/members-vehicles-public/569-oka196-xt-motorhome
 

 
Bicyclecamper


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This is all I needed to know, had seen it stated on some 4wd forums, and just wondered if it was true.

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Whenarewethere


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A replacement element for the Finch fridge seems to be 120 watts which from my understanding run pretty much continuously.

Screenshot_20201210-191443~2.png



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Procrastination, mankind's greatest labour saving device!

50L custom fuel rack 6x20W 100/20mppt 4x26Ah gel 28L super insulated fridge TPMS 3 ARB compressors heatsink fan cooled 4L tank aftercooler Air/water OCD cleaning 4 stage car acoustic insulation.
Jaahn


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Bicyclecamper wrote:

This is all I needed to know, had seen it stated on some 4wd forums, and just wondered if it was true.

 Hi smile

I cannot say exactly, but my opinion is this. Older compressor fridges that had no electronics might have worked direct from a suitable panel. However I think that the modern ones with electronic do-dads and displays and circuit boards will not like the big voltage swings of an unregulated panel direct. I could be wrong, and I do not think warranty will be covered either. 

Having a battery and regulator stabilises the voltage and most items designed for '12V' are designed for this regulated voltage range. The top voltage of the panel is turned off when the regulated battery voltage gets high enough. So as Peter says the regulator output terminals are just switching the battery voltage to the load. 

If you used the 12V element of a 3way fridge it would be simpler and no fancy electronics or controller in the circuit. It would just use the power all the time the sun shines if connected directly to a panel. However a normal 12V panel voltage would still be higher than the element should use so it might burn out soon in full sun. It depends on how well matched the panel was to the element power needs. 

I trust that this reply is not considered too technical ? hmm

Jaahn   



-- Edited by Jaahn on Friday 11th of December 2020 08:28:16 AM

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