Compressor fridge calculation

[bartman]

During our present stay in France and Spain our old 3 way fridge has not been getting anywhere near cold enough, especially on gas. I had decided to give it a service when we return to blighty (or pay someone to do it!), but today one of the push fit pipes on the kitchen tap decided to disengage itself, so I had to spend part of the day dragging the fridge out to get to the underside of the tap. While the fridge was out I came to the conclusion that it was past rescue and the time has come to go with a compressor type.
It looks as though the price difference between the 12v and 230v types is not as great as it was, so I'm looking at a 12v.
I would appreciate some guidance as to whether the present power setup is suitable.
We have 300w of solar on the roof, and 2x110ah lead carbon gel batteries. We usually watch an hour or two of TV in the evening. We do use the van in the winter, but at that time of year we would normally go for ehu so that we can charge our ebike batteries.
I could add more solar but I would have to upgrade the controller to do it.
Any guidance would be welcome

 

[Nesting Zombie]

I’ve had 3 way 12v fridges in the past on all my Livaboard vehicles.
THIS time I bought a standard House slim line Chest freezer BUT with a Fridge function dial that I run from the inverter.
Cheaper to buy, Bigger Capacity, ‘I’ find it better to run & being a ‘Chest’ type Much more efficient I feel, as all the cold air you’ve painstakingly harvested the power for to create STAYS in the space when you ope the lid instead of Spilling out.

Works for me.

 

[Boris7]

Moved to a compressor fridge / freezer earlier this year, Works just great did 4 nights stationary in the south of Portugal in high temperatures with 200ah battery’s and 450watts solar, never missed a beat.

If you drive more and stop over less you’ll not look back, but I guess if you go to Northern Scotland in the winter, drive less and stopover more it may not do so well.

 

[wildebus]

Moved to a compressor fridge / freezer earlier this year, Works just great did 4 nights stationary in the south of Portugal in high temperatures with 200ah battery’s and 450watts solar, never missed a beat.

If you drive more and stop over less you’ll not look back, but I guess if you go to Northern Scotland in the winter, drive less and stopover more it may not do so well.

go to Northern Scotland in the Winter, you could just put any food outside and it would be colder than a Fridge

 

[bartman]

I c

I’ve had 3 way 12v fridges in the past on all my Livaboard vehicles.
THIS time I bought a standard House slim line Chest freezer BUT with a Fridge function dial that I run from the inverter.
Cheaper to buy, Bigger Capacity, ‘I’ find it better to run & being a ‘Chest’ type Much more efficient I feel, as all the cold air you’ve painstakingly harvested the power for to create STAYS in the space when you ope the lid instead of Spilling out.

Works for me.
View attachment 145965

I can see the logic of the chest type - can't accommodate that though in our van

 

[Trotter]

Fwiw, Paul fitted a Adventurer 12v fridge in Demi for me. It was a faff getting the 3 way out . But that was only because of the way Adria fitted it. The Adventurer went in, no problem as it’s virtually the same size as the Dometec it replaced.
Yes I know that I have plenty of power in the van, I’ve not turned the fridge off since it went in. The only downside I’ve found is the freezer only gets down to about-5. There’s a chest freezer in the van, so that’s not a problem.

 

[Trotter]

I c

I can see the logic of the chest type - can't accommodate that though in our van

I did try a chest fridge. I found that food got damaged when delving through it trying to find stuff at the bottom.

 

[Pudsey Bear]

Don't your tits get a bit cold?

 

[bartman]

Don't your tits get a bit cold?

Oh well, at least nobody's mentioned lithium (so far )

 

[Robmac]

Oh well, at least nobody's mentioned lithium (so far )

Doh!

That's another fiendish plan gone out of the window!

 

[trevskoda]

Strange thing is my small fridge has no open vents and is sealed, but i put 2 vents above to let air around it which may stop mould or damp.

 

[Okta]

I have a 12v compressor fridge. I have now been offgrid for 24 hours and have used 46Ah of battery. A good chunk of that would have been running my CPAP overnight for 8 hours, it also includes 2 hours of tv and a few hours of gas hot air heating. I would estimate the fridge probably took less than 20Ah. In warmer weather it might use more, possibly 30Ah. It is a Thetford 12v compressor fridge and doesn’t disturb us at all.

 

[dhall26]

My Isotherm 115 Litre fridge uses between 25Ah and 30Ah depending on the ambient temperature per day.

 

[trevskoda]

My Isotherm 115 Litre fridge uses between 25Ah and 30Ah depending on the ambient temperature per day.

My small fridge uses a qtr of a amp an hr, 250mA, its a tripple a rated fridge and sealed.

 

[wildebus]

I have a 12v compressor fridge. I have now been offgrid for 24 hours and have used 46Ah of battery. A good chunk of that would have been running my CPAP overnight for 8 hours, it also includes 2 hours of tv and a few hours of gas hot air heating. I would estimate the fridge probably took less than 20Ah. In warmer weather it might use more, possibly 30Ah. It is a Thetford 12v compressor fridge and doesn’t disturb us at all.

I doubt the fridge took less than 20Ah.

 

[Robmac]

My small fridge uses a qtr of a amp an hr, 250mA, its a tripple a rated fridge and sealed.View attachment 145968

Am I understanding this right Trev, 6 Amps a day through an inverter?

 

[trevskoda]

Am I understanding this right Trev, 6 Amps a day through an inverter?

What it says on the tin Rob, i did tests when wildbus was doing his, my we fridge ran 24hrs on a 90ah lead acid with no probs, i was however using a 600w smart inverter which goes into sleep mode untill a signal for power starts it up again.

 

[Robmac]

What it says on the tin Rob, i did tests when wildbus was doing his, my we fridge ran 24hrs on a 90ah lead acid with no probs, i was however using a 600w smart inverter which goes into sleep mode untill a signal for power starts it up again.

At 1 amp every 4 hours Trev so 6 amps a day then that would mean it would run for 15 days on a 90ah battery, or am I calculating it wrongly?

 

[Robmac]

At 1 amp every 4 hours Trev so 6 amps a day then that would mean it would run for 15 days on a 90ah battery, or am I calculating it wrongly?

Sorry, that's not taking into account Depth of Discharge!

 

[undertaker]

Recently replaced our van and the replacement came with a thetford 12v 84ltr compressor fridge. Was unsure but we are really impressed with it. Firstly, it is effective, cooling down to 2 or 3 degrees soon after switching it on. Also the freezer box keeps stuff frozen. We are comfortable travelling with the fridge full whereas the 3 way always struggled on 12v when driving. Regarding energy efficiency, during the 30c heatwaves we had this summer it was drawing 20 ah per 24 hrs (nothing else of significance electrical being used, water pump, occasional led light on ). The 160w roof mounted solar was replacing 10ah during the 24 hour period, so the net use was 10ah per day. I would say the set up you have outlined in your motorhome should cope OK. I wouldn't like to go back to a 3 way fridge.