Running fridge on solar panel

Jac Sprat

Jac Sprat

Joined
Feb 19, 2015
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Norfolk
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35,161
MH
Globecar Campscout 2013
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Since 2016
Good morning.
A few questions around running the fridge from our large solar panel on the roof.
Will it run the fridge ? I’ll be at a festival without hookup.
Will it affect the car battery at any point? Doesn’t it top that up?
Any thoughts appreciated.
 
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It won't run directly. You will need to run it off the battery which in turn gets topped up by the solar. It depends on the fridge and your set up as to whether it can be done. It also depends how much solar/battery you have as to whether it will work or just ruin your batteries.

There is a solar controller (someone else will know which) that has a fridge output that only sends power to the fridge when it thinks there is enough spare power.

Can you not run your fridge on Gas? Is it a 3 way fridge absorption fridge or a compressor fridge?
 
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thanks
It just doesn't seem to work on gas.
 
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Can you not run your fridge on Gas? Is it a 3 way fridge absorption fridge or a compressor fridge?
We don’t know I’m afraid! What does that mean? We have a choice of what to run it on gas/electric etc

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gas is best for of grid when you say it doesnt work on gas do you mean it doesn't light or doesnt work when its alight?
 
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if its got a small flame its goin to be either the burner is full of crap or the injectors blocked plenty of you tube videos to show how to deal with it
 
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Most motorhomes have a 3-way fridge, that works from 240V, 12V or gas. These fridges are not very efficient, and take a lot of power when running on 12V. So you'd need several hundred watts of solar panel to run one of these. And at least a couple of big batteries to store enough to last overnight.

If you have a compressor fridge, with no gas option, these are a lot more efficient. If you have a large panel (200W or more) then it is quite possible that this will be enough. The idea is that the solar panel powers the fridge and fills up the battery during daylight, and the battery powers the fridge overnight.

A compressor fridge typically uses about 30 to 40 Ah per day, A 200W panel will typically yield about twice that, so enough for the fridge plus some for the other electrics.

Edit: I see that your fridge is a 3-way. It's not really feasible to run a 3-way fridge on 12V from batteries. It could easily use 300Ah of charge in 24 hours. OK for an hour or two, but not for a festival of several days.

You can usually access the gas burner by removing the lower external vent. There will be a tall metal cylinder filled with rockwool, and at the bottom there is a gas pipe and several electric wires leading to it. The burner is somewhere at the bottom of the cylinder.
 
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Thanks. We do have a large roof top solar panel so we’ll try that. They had to use a crane to get it on

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A 3 x way absorption fridge is the type that can be operated on gas when there is no EHU , 240v when there is EHU available or 12v , but only when engine is running. (otherwise it will flatten the battery in a short time)
Most Motorhomes are normally wired so the absorption type fridge will only cool on 12v when the engine is running to prevent flat battery problems.
 
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Just backing up what most have said above. Seems like you have an absoption fridge, my understaning is that even on 12v operation this setting only helps to maintain the temperature and does not actually provide any cooling. Plus power consumption is high.
Maybe it needs a service for the gas operation ? Clean of the flu, burner and change the thermal paste are often mentioned on here. Along with fridge fans.

On route to the recent 3F Fun rally i treated myself to one of these... Ran it off the 2 x lead acid batteries and 2 x solar panels (size unknoen but assume 100-120w each). Worked really well. Cold beer and tonic water (y)

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Thanks, so will running it on the fridge electric setting off grid with no hook up drain the car battery? Won’t it run off the leisure battery on the electric setting?
Sorry if I’m being a bit slow here.
 
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You need to get the gas fixed as it is the most efficient way to run the fridge.
A 3 way fridge can only run in on 12 v for a few hours a day due to the high current required.


I have a Votronic Solar regulator (needs to be a 250 or higher) which has an AES output that you wire to the fridge S+ connection (Dometic fridges from about 2010). When the batteries are fully charged and there is plenty of solar the fridge switches to 12v, it does it in ½ hr blocks to avoid flattening the batteries. often the fridge will run for two or three hours a day on 12v.

The fridge needs to be an AES fridge with electronic gas ignition & needs to have a permanent high power 12v feed from the hab battery. My Elektroblock automatically switches the fridge from starter battery to hab battery when the engine is not running.

Dometic fridges have very dumb firmware and have Solar as the prority power source so when on mains if the fridge sees a signal on the S+ and switches to 12v even though you are on EHU, you can fit a switch inline with the AES connection from the regulator or do as I did which was to fit a mains powered relay.

Also not worth doing unless you have around 300 Watts or more of solar.
 
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It would not normally run on12v without the engine running as the starter battery should be supplying the power for 12v cooling , (engine running), although the leisure battery may be being used to power the fridge controls which use little power.
If you are able to run your fridge cooling from your leisure battery you will flatten it in a short time.
As LennyHB has said gas operation of the fridge is the answer to running the fridge without EHU or when the engine is not running and that is the way 3 x way fridges are designed

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Jac Sprat said:
Thanks, so will running it on the fridge electric setting off grid with no hook up drain the car battery? Won’t it run off the leisure battery on the electric setting?
Sorry if I’m being a bit slow here.
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That depends on which battery is supplying your fridge with 12v power, some vans use starter battery some use habitation but either way a 3 way (Gas/240v/12v) fridge on 12v needs more power than either battery can supply reliably even with solar panels so your choice is get the gas sorted or run a 12v compressor cool box which are far more efficient.
 
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GeoffnDee said:
It would not normally run on12v without the engine running as the starter battery should be supplying the power for 12v cooling , (engine running), although the leisure battery may be being used to power the fridge controls which use little power.
If you are able to run your fridge cooling from your leisure battery you will flatten it in a short time.
As LennyHB has said gas operation of the fridge is the answer to running the fridge without EHU or when the engine is not running and that is the way 3 x way fridges are designed
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That's not strictly true as there are plenty of vans around that have the fridge powered from the habitation batteries, when on AES or Automatic mode the fridge detects the engine run signal and turns the fridge onto 12v wherever it comes from, if you manually select 12v it should then run from whichever battery it is connected to.
 
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funflair said:
That's not strictly true as there are plenty of vans around that have the fridge powered from the habitation batteries, when on AES or Automatic mode the fridge detects the engine run signal and turns the fridge onto 12v wherever it comes from, if you manually select 12v it should then run from whichever battery it is connected to.
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Yep, on every Hymer we have had there is a relay in the EBL that switches the 12v to the fridge from the starter battery with the engine to to the hab battery when the engine is not running. Then if you select 12v on the fridge without the engine running it will run from the hab battery.
 
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It's looking like getting the gas operation repaired or keep the engine running all weekend!
Gas really seems to be your best option.
 
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Jac Sprat said:
Thanks, so will running it on the fridge electric setting off grid with no hook up drain the car battery? Won’t it run off the leisure battery on the electric setting?
Sorry if I’m being a bit slow here.
Click to expand...
It depends on the details of your wiring. The standard method is to connect to the starter battery, via a relay that is switched on by the D+ (engine running) signal. So normally the fridge is only on when the engine is running. The alternator is producing power, and is charging the starter battery, powering the fridge element and also charging the leisure battery. So although the fridge is connected to the starter battery, the power always comes from the alternator, not the starter battery.

Many motorhomes simply don't have the facility to run the fridge from 12V when the engine is stopped. Of those that do, the ones I've seen take power from the leisure battery, not the starter battery. There's nothing to stop you fitting a switch that will send power from the leisure battery to the fridge if that's what you want. But generally the downside of this (flat leisure battery fairly quickly) is such that most MH manufacturers don't bother.
 
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