Compressor Fridge.

[PeteMallorca]

Hi, if I put in a small compressor fridge, 240v 200kwh per annum, how much battery will that use daily (24 hrs), from a 12v bank?

At the moment, I'm still running on 3 x 100AH Gell batteries but soon to be changing over to 3 x 200AH LifePo4.

I have got 200W of panels but will be increasing to 900W to1000W soon.

I also have a 2.2Kw generator, to top up when nesecery.

Thanks for your help.

 

[Jim]

I have a dometic compressor beer fridge going 24/7 in the back of our panel van, it's never off even when at home. Don't know how much leccy it uses. I keep it set at 1c which keeps my Birra at a very drinkable temperature. We have 300watts of solar and 200AH of Lithium and we are never on a hookup and the beer is always cold

 

[berni109]

What's the watts or amp rating on the fridge?
How big is your inverter?

 

[autorouter]

200kWh per year is 200000 / 365 = 548Wh per day. That's equal to 548 / 12 = 46Ah per day from a 12V battery bank. That's just a mathematical calculation. You need to add at least 10%, maybe 20%, for conversion losses in the inverter, manufacturer's optimism etc.

That's comparable to the consumption of a 12V compressor fridge, so it's definitely a viable option. Your 200W of solar should give you about 60Ah to 80Ah per day in reasonable weather. People seem to find about 200W of solar is enough in summer, but 300W and a nice big battery bank gives you enough margin to tide you over a bad spell of weather. This may be of interest:

 

[PeteMallorca]

I have a dometic compressor beer fridge going 24/7 in the back of our panel van, it's never off even when at home. Don't know how much leccy it uses. I keep it set at 1c which keeps my Birra at a very drinkable temperature. We have 300watts of solar and 200AH of Lithium and we are never on a hookup and the beer is always cold

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[PeteMallorca]

What's the watts or amp rating on the fridge?
How big is your inverter?

I only have the kwh yearly, 200.

 

[PeteMallorca]

200kWh per year is 200000 / 365 = 548Wh per day. That's equal to 548 / 12 = 46Ah per day from a 12V battery bank. That's just a mathematical calculation. You need to add at least 10%, maybe 20%, for conversion losses in the inverter, manufacturer's optimism etc.

That's comparable to the consumption of a 12V compressor fridge, so it's definitely a viable option. Your 200W of solar should give you about 60Ah to 80Ah per day in reasonable weather. People seem to find about 200W of solar is enough in summer, but 300W and a nice big battery bank gives you enough margin to tide you over a bad spell of weather. This may be of interest:

Thank you so much autorouter...... That's what I was looking for. My existing system should survive with maybe a little help. Until the lifepo4 are connected. Thank you very much.

 

[Richard n Ann]

My compressor fridge uses about 1ah on average iirc... So 24ah a day

 

[PeteMallorca]

My compressor fridge uses about 1ah on average iirc... So 24ah a day

 

[Boldly]

We have a bog standard Currys under counter 240v fridge freezer and it uses between 50 and 70 ah a day depending on weather how full it is etc. We have 210 ah of lead battery and 295 watts solar. Has worked fine at Drax and pershore in cloudy and rainy weather. Has struggled the last few days through France and northern Spain as the weather has been horrendous. Now recovered and should be ok. Did find bad earth on split change so was not charging when driving. All ok now.

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[PeteMallorca]

Thanks

 

[PeteMallorca]

Thanks Boldly. I'm in mallorca. I feel your pain

 

[gerry mcg]

Our 65l dometic fridge is rated at something like 2AH, so in theory, that's 48A /24h. But at the working setting, the fridge compressor is only running 39% of the time, so average consumption is 0.7Ah /16A per 24h.
In practice., 175W solar keeps the battery topped up easily

 

[PeteMallorca]

Our 65l dometic fridge is rated at something like 2AH, so in theory, that's 48A /24h. But at the working setting, the fridge compressor is only running 39% of the time, so average consumption is 0.7Ah /16A per 24h.
In practice., 175W solar keeps the battery topped up easily

Thanks Gerry, I've heard that they are very efficient.

 

[Hoovie]

Thanks Gerry, I've heard that they are very efficient.

I don't think they are THAT efficient I would say the "2Ah" value is likely to be the AVERAGE hourly consumption INCLUDING taking into account the off time.
The numbers quoted previously at around the 50Ah/Day are much more likely to be the case and would also tie up with what I have experienced on multiple compressor fridges.

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[gerry mcg]

I don't think they are THAT efficient I would say the "2Ah" value is likely to be the AVERAGE hourly consumption INCLUDING taking into account the off time.
The numbers quoted previously at around the 50Ah/Day are much more likely to be the case and would also tie up with what I have experienced on multiple compressor fridges.

I can only report my findings, which is my fridge draws round 2A when the compressor is running, and 0A when it is not. At 3C in the fridge, the compressor is running about 30% of the time.

 

[Reevsie]

I fitted a Thetford 1260 compressor fridge last month. I also fitted a meter in-line to see how much it uses. Over 30 days it used an average of 44.16AH per day, so it averages out at 1.84AH per hour. That is keeping my fridge down to 3 degrees and my freezer down to 18 degrees.

From memory when I was fitting the fridge and I switched it on for the first time the draw was just under 4.2AH on its highest setting. But as mentioned the compressor is not on all the time.

 

[PeteMallorca]

The fridge is in and had its first test. It went down to 2.7°c fridge and -18°c freezer, quickly.

I'm still using the old inverter (Edecoa 3000W) and batteries (3 × 100AH gell) but it's got me thinking, after having the inverter on 24hrs.

Would I be better off with a small dedicated inverter, for the fridge only? I have a multiplus ll 12v 3000 120 going in soon but I'm not sure that I want that draining the 600AH lufepo4 batteries that are going in, for 24hrs a day.

These are the readings that I got.

On my Smartshunt:
Permanant drain on 12v side = 1.7A - 20W. Roughly.
When I turn on the inverter, with zero load, the drain goes up to about 4.5A to 4.8A - 55W to 59W.
Highest readings on SmartShunt were 10.31A - 131W But were usually about 9.4A - 114W, with the fridge compressor running.

240v Energy Meter readings were (Low) 6.2W and (High) 339W.

What size inverter would you all suggest, for the lowest zero load power usage?

Thanks.

 

[Boldly]

I was told that the 240v readings are not reliable if fed by inverter. Indeed every time I try I get a different reading so I think this must be so.
I don't have a shunt but using a clamp meter mine uses 6.7 amps when running. Spare inverter 7.7 amps so more loss on conversion. Neither are pure sine wave though.

 

[PeteMallorca]

I was told that the 240v readings are not reliable if fed by inverter. Indeed every time I try I get a different reading so I think this must be so.
I don't have a shunt but using a clamp meter mine uses 6.7 amps when running. Spare inverter 7.7 amps so more loss on conversion. Neither are pure sine wave though.

Thanks Boldly, I just feel that a dedicated, small inverter, could save mea lot of battery use.

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[autorouter]

What size inverter would you all suggest, for the lowest zero load power usage?

Generally the smaller the inverter, the lower the zero power load, but that's not the whole story. For inverters of the same power, usually the more expensive the lower the zero load power.

Also some inverters, Victron for example, have various modes for zero power. A fridge has a thermostat which switches the compressor off for extended periods. The Victron inverters shut down in two stages, with reduced zero load power. So that means it might take a second or two to wake up when the compressor comes on again, but that shouldn't be a problem for a fridge.

The other question is the minimising the power rating of the inverter. The compressor has an input surge current, so you want an inverter that has a good surge rating. Victron for example. As to the lowest rating you can get away with, you'd have to actually try it, or ask someone who has. I'm sure the 500W Victron would be OK, and maybe the 375W Victron would be OK too.

 

[PeteMallorca]

Generally the smaller the inverter, the lower the zero power load, but that's not the whole story. For inverters of the same power, usually the more expensive the lower the zero load power.

Also some inverters, Victron for example, have various modes for zero power. A fridge has a thermostat which switches the compressor off for extended periods. The Victron inverters shut down in two stages, with reduced zero load power. So that means it might take a second or two to wake up when the compressor comes on again, but that shouldn't be a problem for a fridge.

The other question is the minimising the power rating of the inverter. The compressor has an input surge current, so you want an inverter that has a good surge rating. Victron for example. As to the lowest rating you can get away with, you'd have to actually try it, or ask someone who has. I'm sure the 500W Victron would be OK, and maybe the 375W Victron would be OK too.

Thank you autorouter I was thinking the victron 500 to be sure. I guess it's time to bite the bullet and see.

Thanks

 

[Borsuk]

I have put a domestic fridge freezer in my van to replace the previous Dometic TecTower. I tried a 600 watt inverter that I have in my bike trailer but that couldn't cope with the startup current. I settled for a Renogy 2kw pure sine wave inverter with mains by pass for when on hookup. The fridge works fine on that. Solar panels have the batteries back up to full by lunchtime most days. I have 520w of solar but this time of year I am maxing around 200w. Fridge averages 50 - 60 watts overall cycle power, depending of course on how often the doors are opened.