12vdc Fridges - Average Power Used?

[wildebus]

I’ve recently installed a Dometic CRE80 in place of the old 3way in our camper.

We have just got back from 3 nights away to test it, the Victron Orion Smart 12 12 30 B2B charger and new 285ah deep cycle lead leisure batteries Ive installed work as expected.

We also wanted to see how long our Eco Flow River pro Lithium battery (62ah) will take the day to day strain of powering the fridge as it recharges fast off the generator whenever that is convenient/possible.

All works fine but I’m still unsure as to how much power the fridge is likely to draw on average as we saw it use 30ah and then 60ah in two days of similar use & weather conditions.

Anyone got some figures for actual battery use for similar dc fridges?

Ok, a few comments ....

A typical decent Compressor Fridge will use around 1.5Ah/Hr average. When running it will be around 4A, but the compressor only runs part of the time, so it averages at around 1.5A.
In hot weather, the power consumption goes up notably - on the official figures, it can nearly double. For most people, that does not matter massively as if they are wild-camping, they typically have solar and the solar in hot (so sunny usually) brings in more power then when overcast and cooler. As you DON'T have solar, the increased consumption could be an important factor (so maybe as I suggesed, a portable solar kit could be handy?)
USING the fridge makes a remarkable difference as well. when I say "using", I mean opening door to take food out, put food back, etc. The official figures and most consumption data (including mine) will be based on the door kept closed. I have noticed that when I look at my power logging for the fridge, I can actually tell very easily when I load it up or do any kind of re-arranging - the 'cool' goes very quickly through an open door and much faster than you might imagine. I wonder if that was a factor in your 30Ah vs 60Ah power use days?

Now on power use, I found my Waeco 50CRX would run for just about 2 days on a pair of 100Ah Lead Acid batteries until they dropped to 50% - so that would be 100Ah taken out in those 2 days. that is around about the same as your findings by the look of it (90Ah in two days).
Now of course bear in mind you are not only running the fridge, but using lights or whatever. My 240V Compressor Fridge uses significantly less power per day than the Motorhome habitation system generally when I am using it, so my battery bank is not sized to support the fridge but using what I want to use. Unless you are very frugal, off-grid and with no solar, you will be using that generator a fair bit I would guess?

As you have fitted the Compressor Fridge where the old 3-Way fridge is, you could take advantage of the venting and fit a cooling kit if you think the fridge migght be getting hot and so less efficient?
I fitted a "proper" cooling kit to mine. When I say "proper" I simply mean a commercially packaged all-in-one kit with temperature-controlled speed control and a nice little control panel. You can obviously rig up your own more cheaply, but I decided to treat myself
I found the fans fitted perfectly on the Thetford mesh vent screen ...

 

[Nabsim]

Funnily enough averaged out I don’t seem to get much difference in power consumption between hot and cold weather or summer and winter. It may be partly because I don’t open the door very often, don’t have milk in tea/coffee and don’t drink alcohol or fizzy drinks so not going for cold cans.

I can only work off my battery monitor, I don’t have anything measuring just my fridge but I know usually what’s drawing power at any given time so have a pretty good idea.

I don’t turn my fridge off overnight as I hear quite a few do, that may be something to eek out your power drain a little maybe? January into February this year I tried not using the fridge and the difference was amazing even though I knew my fridge was my main user. I don’t think I will bother again though as with the fridge and freezer with just me and the dogs I can easily do three weeks between shops and still me eating nice veggies

 

[r4dent]

Both our Waeco chest fridge
AND 240v under counter/Victron inverter fridges hit an average of 4 amps kicking in about once an hour for a few minutes (usually around 3 to 4 minutes when fridges in use)
Less when stuff is just shut up

I assume that is 4 amp at 230v (about 50 amp at 12v).

no, that will be 4A at 12V. Around 50W.

I don't think ANY normal fridges draw close to around 1000W in use!

Domestic fridges have a max watt of around 800w, which would be just under 4 amp @ 230v.

How Many Watts Does a Refrigerator Use? [Or Mini-Fridge] - EnergyBot

The average home refrigerator uses 350-780 watts. Click to learn how you can find how much your specific model uses, including mini-fridges.

www.energybot.com

MrIceman stated the fridges runs for about 1.5 hours a day (24 * 4 mins)

If the 4a is at 230v
4 amp x 230v * 1.5hrs = 1380 wh per day = 1380 * 365 wh per year = 500 kwh per year

If the 4a is at 12v
4 amp x12v * 1.5hrs = 72 wh per day = 72 * 365 wh per year = 27kwh per year

An efficient modern 230v fridge uses around 100 kwh per year.

I still think 4amp @ 230v is more realistic.

I am hoping MrIceman will clarify the situation.

 

[Robmac]

Funnily enough averaged out I don’t seem to get much difference in power consumption between hot and cold weather or summer and winter. It may be partly because I don’t open the door very often, don’t have milk in tea/coffee and don’t drink alcohol or fizzy drinks so not going for cold cans.

I can only work off my battery monitor, I don’t have anything measuring just my fridge but I know usually what’s drawing power at any given time so have a pretty good idea.

I don’t turn my fridge off overnight as I hear quite a few do, that may be something to eek out your power drain a little maybe? January into February this year I tried not using the fridge and the difference was amazing even though I knew my fridge was my main user. I don’t think I will bother again though as with the fridge and freezer with just me and the dogs I can easily do three weeks between shops and still me eating nice veggies

I'm sorry Neil but that doesn't make sense.

Not drinking alcohol is just plain wrong.

 

[Nabsim]

I'm sorry Neil but that doesn't make sense.

Not drinking alcohol is just plain wrong.

No but probably helps me reduce my power use

 

[MrRob]

Thank you all for the info and advise. I’m hoping 60ah a day is towards the top end of usage, if so we can manage that load with the generator and lithium power pack at least in the short term.

Ok, a few comments ....

A typical decent Compressor Fridge will use around 1.5Ah/Hr average. When running it will be around 4A, but the compressor only runs part of the time, so it averages at around 1.5A.
In hot weather, the power consumption goes up notably - on the official figures, it can nearly double. For most people, that does not matter massively as if they are wild-camping, they typically have solar and the solar in hot (so sunny usually) brings in more power then when overcast and cooler. As you DON'T have solar, the increased consumption could be an important factor (so maybe as I suggesed, a portable solar kit could be handy?)
USING the fridge makes a remarkable difference as well. when I say "using", I mean opening door to take food out, put food back, etc. The official figures and most consumption data (including mine) will be based on the door kept closed. I have noticed that when I look at my power logging for the fridge, I can actually tell very easily when I load it up or do any kind of re-arranging - the 'cool' goes very quickly through an open door and much faster than you might imagine. I wonder if that was a factor in your 30Ah vs 60Ah power use days?

Now on power use, I found my Waeco 50CRX would run for just about 2 days on a pair of 100Ah Lead Acid batteries until they dropped to 50% - so that would be 100Ah taken out in those 2 days. that is around about the same as your findings by the look of it (90Ah in two days).
Now of course bear in mind you are not only running the fridge, but using lights or whatever. My 240V Compressor Fridge uses significantly less power per day than the Motorhome habitation system generally when I am using it, so my battery bank is not sized to support the fridge but using what I want to use. Unless you are very frugal, off-grid and with no solar, you will be using that generator a fair bit I would guess?

As you have fitted the Compressor Fridge where the old 3-Way fridge is, you could take advantage of the venting and fit a cooling kit if you think the fridge migght be getting hot and so less efficient?
I fitted a "proper" cooling kit to mine. When I say "proper" I simply mean a commercially packaged all-in-one kit with temperature-controlled speed control and a nice little control panel. You can obviously rig up your own more cheaply, but I decided to treat myself
I found the fans fitted perfectly on the Thetford mesh vent screen ...
View attachment 108619

That all makes sense to me.

Do you have a link for the cooling fans please? as that might save me making one and it failing to achieve anything like with the old fridge where it seemed to make things worse.

We just used the fridge as normal for the test

The last 10 years we haven’t tended to stay put for more that two nights and only tend to use phones, tablets and lights in the evenings with generator power for Microwave or habitation AC if we ever needed it off grid.


Although most of the last 4/5 year we have had to hook up anyway if we wanted cool things in the fridge so perhaps we need to re-learn how to fridge.

 

[wildebus]

This is the fan kit I bought - https://amzn.to/38sl9A3
It is not cheap at £57, and you will get posts saying you can do your own for a lot cheaper, and I could have done that myself as well, but I don't regret buying the kit and I would actually get the same kit again.

 

[wildebus]

Domestic fridges have a max watt of around 800w, which would be just under 4 amp @ 230v.

How Many Watts Does a Refrigerator Use? [Or Mini-Fridge] - EnergyBot

The average home refrigerator uses 350-780 watts. Click to learn how you can find how much your specific model uses, including mini-fridges.

www.energybot.com

MrIceman stated the fridges runs for about 1.5 hours a day (24 * 4 mins)

If the 4a is at 230v
4 amp x 230v * 1.5hrs = 1380 wh per day = 1380 * 365 wh per year = 500 kwh per year

If the 4a is at 12v
4 amp x12v * 1.5hrs = 72 wh per day = 72 * 365 wh per year = 27kwh per year

An efficient modern 230v fridge uses around 100 kwh per year.

I still think 4amp @ 230v is more realistic.

I am hoping MrIceman will clarify the situation.

Very few will be that high and no current domestic fridges are close. I KNOW mriceman was meaning 4A at 12V. That information has been shared on previous similar threads.
I can tell you now that 4A at 230V is NOT CORRECT.
Your maths are flawed. You are assuming the duty cycle is 6% whic is very low (it may be correct but it would be unusual). Why do you assume that number as a standard? You are extrapolating a post with an assumption of information, you do not know what fridge he has in terms of efficiency, and combining it with a website with unstantiated data to get a faulty conclusion.


Here is an REAL example of a domestic compressor fridge and its power use:
Over a 6 hour period, it is on (i.e. Compressor running) for approx 60 minutes - that is a 17% duty cycle (around 3 times your assumption).
The power draw whilst running is an average of 55W - on a 12V system, that would be approx 4.5A

 

[mistericeman]

Domestic fridges have a max watt of around 800w, which would be just under 4 amp @ 230v.

How Many Watts Does a Refrigerator Use? [Or Mini-Fridge] - EnergyBot

The average home refrigerator uses 350-780 watts. Click to learn how you can find how much your specific model uses, including mini-fridges.

www.energybot.com

MrIceman stated the fridges runs for about 1.5 hours a day (24 * 4 mins)

If the 4a is at 230v
4 amp x 230v * 1.5hrs = 1380 wh per day = 1380 * 365 wh per year = 500 kwh per year

If the 4a is at 12v
4 amp x12v * 1.5hrs = 72 wh per day = 72 * 365 wh per year = 27kwh per year

An efficient modern 230v fridge uses around 100 kwh per year.

I still think 4amp @ 230v is more realistic.

I am hoping MrIceman will clarify the situation.

Yup 4a 12v (though there is obviously a very short spell of 'inrush' as the inverter kicks in...

Kicks in about once an hour (obviously when your not in and out of it for wine)
The Waeco actually runs slightly less on average being a chest type, so the cold air doesn't flood out when you open it...

 

[Canalsman]

Ok, a few comments ....

A typical decent Compressor Fridge will use around 1.5Ah/Hr average. When running it will be around 4A, but the compressor only runs part of the time, so it averages at around 1.5A.
In hot weather, the power consumption goes up notably - on the official figures, it can nearly double. For most people, that does not matter massively as if they are wild-camping, they typically have solar and the solar in hot (so sunny usually) brings in more power then when overcast and cooler. As you DON'T have solar, the increased consumption could be an important factor (so maybe as I suggesed, a portable solar kit could be handy?)
USING the fridge makes a remarkable difference as well. when I say "using", I mean opening door to take food out, put food back, etc. The official figures and most consumption data (including mine) will be based on the door kept closed. I have noticed that when I look at my power logging for the fridge, I can actually tell very easily when I load it up or do any kind of re-arranging - the 'cool' goes very quickly through an open door and much faster than you might imagine. I wonder if that was a factor in your 30Ah vs 60Ah power use days?

Now on power use, I found my Waeco 50CRX would run for just about 2 days on a pair of 100Ah Lead Acid batteries until they dropped to 50% - so that would be 100Ah taken out in those 2 days. that is around about the same as your findings by the look of it (90Ah in two days).
Now of course bear in mind you are not only running the fridge, but using lights or whatever. My 240V Compressor Fridge uses significantly less power per day than the Motorhome habitation system generally when I am using it, so my battery bank is not sized to support the fridge but using what I want to use. Unless you are very frugal, off-grid and with no solar, you will be using that generator a fair bit I would guess?

As you have fitted the Compressor Fridge where the old 3-Way fridge is, you could take advantage of the venting and fit a cooling kit if you think the fridge migght be getting hot and so less efficient?
I fitted a "proper" cooling kit to mine. When I say "proper" I simply mean a commercially packaged all-in-one kit with temperature-controlled speed control and a nice little control panel. You can obviously rig up your own more cheaply, but I decided to treat myself
I found the fans fitted perfectly on the Thetford mesh vent screen ...
View attachment 108619

One observation.

You would do well to blank off the grille on either side of the fans. Without doing that you reduce the efficiency because the fans draw air from the sides as well as from below.

 

[r4dent]

Your maths are flawed.

My math is NOT flawed.
Saying my math is flawed is like a red rag to a bull, (I studied Maths at University)
I agree that the answers are outside the anticipated range and this made me to suspect the data which is why I sought clarification from mistericeman.

You are assuming the duty cycle is 6% Why do you assume that number? Why do you say the fridge is running for 1.5 hours in a 24 hour period?

Saying that I assume is more of a red flag than saying my maths is flawed.
I'm Not assuming 6%, it is what mistericeman said it was using .

Kicking in about once an hour for a few minutes (usually around 3 to 4 minutes)

4 minutes every hour =4 /60 = 6.7 %.
4 minutes every hour =4 x 24 = 96 minutes per day

Why do you assume that number as a standard? You are extrapolating a post with an assumption of information, you do not know what fridge he has in terms of efficiency, and combining it with a website with unstantiated data to get a faulty conclusion.

Again, I never assumed 6.7% to be a standard. I never referred to a fridge other than his.
I do agree that the data is unstantiated [sic].

that is a 17% duty cycle (around 3 times your assumption).

Again 6.7% is not an assumption by me, it is based on incorrect data.
Your estimated 17% is just over 10 minutes every hour (around 3 times mistericeman’s statement)

Using 17% then 4 amp @ 12v gives a far more realistic annual usage.
4 amp x12v x 24hrs x 17% = 200wh per day = 200 * 365 wh per year = 73kwh per year.
An efficient modern 230v fridge uses around 100 kwh per year.

Still friends?

 

[MrRob]

One observation.

You would do well to blank off the grille on either side of the fans. Without doing that you reduce the efficiency because the fans draw air from the sides as well as from below.

It’s going in horizontal between the back of fridge and van wall above top of the vent opening. I’ve got a chunky vent and gas pipes to avoid.
I’ll experiment with foam baffles to channel the flow of cool air and or stop warm air back flow into the fridge fan.

 

[saxonborg]

One observation.

You would do well to blank off the grille on either side of the fans. Without doing that you reduce the efficiency because the fans draw air from the sides as well as from below.

Just an observation, that air drawn in at the sides would be the same ambient temperature as the air being pulled into the bottom vent so do you think baffling each side of the fans would make a big difference?

 

[wildebus]

One observation.

You would do well to blank off the grille on either side of the fans. Without doing that you reduce the efficiency because the fans draw air from the sides as well as from below.

I am not sure if I understand what you mean - or if it would matter either TBH?

 

[MrRob]

I think the potential issue is that the fans might just circulate cold air in and out of the grill without it being pushed up the back of the fridge to the top where the work is done. And the already hot air that is just circulating up by the fridge fan too. I’m pretty sure that’s what happened with my attempt to improve things with the 3way.

 

[MrRob]

A contrary thought … if I put my big floor fan in my doorway it pushes air a long way into the house. Enclosing the gap around it might make it more efficient but probably not worth the effort… I guess it depends how strong the fan is.

 

[Fazerloz]

I am not sure if I understand what you mean - or if it would matter either TBH?

Personally I would think it could make matters worse by blanking. with your fans been temp controlled. Blanking would reduce the natural convection making your fans have to kick in far more often than they do normally. I am assuming they do not run every time the comp kicks in and only when needed.

 

[wildebus]

Personally I would think it could make matters worse by blanking. with your fans been temp controlled. Blanking would reduce the natural convection making your fans have to kick in far more often than they do normally. I am assuming they do not run every time the comp kicks in and only when needed.

They are temp/speed controlled. kick in at a certain temp, speed increasing as (if) temp increases. Plus a manual override with speed selections. (this is why I would get the kit again - very nicely designed setup)

Fitted the controller behind the table storage cupboard for easy access if needed ...

 

[trevskoda]

How come there is no cooling piping on the back of my we fridge, its all closed in and you can hardly hear it run, I did put vents above just to keep air around it and to stop any damp or smells

 

[Fazerloz]

They are temp/speed controlled. kick in at a certain temp, speed increasing as (if) temp increases. Plus a manual override with speed selections. (this is why I would get the kit again - very nicely designed setup)

Fitted the controller behind the table storage cupboard for easy access if needed ...
View attachment 108638

Do you have the fans in the top sucking hot out or in the bottom blowing cold in.