Compressor fridges

[GUlewis]

Hi all,
I'm seriously considering a compressor fridge, more likely a waeco CR140, for my next caravan and I'm seeking anyone's advice who has this style of fridge instead of the three way. I do a lot of free camping so will need to rely on a good battery and solar set up. Currently looking at two 100amp/hr batteries and two to three solar panels either 120w or 150w. Will this be sufficient for three to five days off the grid without having to run a generator. What have others experienced and what size set ups are you using?

Thanks

 

[Bushman]

I considering compressor fridge next time, though most of our free camps are generally one or two nights on the way to somewhere then it's either parks or showground

I have a mate that does van solar installation/upgrades and other accessories, he recommends minimum 400 watts of solar for compressor fridge set ups in vans with minimum 2 X batteries

 

[millers]

Have had a compressor fridge in a previous van, but not set up for free camping. Operated from 12V car or 240V connection with auto switchover.

Reason for change was consistent operation, could not get fridge temp right and would loose a lot of food. I think we have this right in the expanda and also use a temperature monitor.

I found a comparison chart here https://www.caravanrvcamping.com.au/caravan-fridge-comparison-chart and I assume that there is a lot of them about.

Taking one as an example Vitrifrigo DP150i Compressor Fridge the figures are:

Max current draw (12V): 3.3 Amps from https://www.vitrifrigofridges.co.uk/dp150ifridge.htm but comparison chart indicates 54W (4.5 Amps) with an average of 28W (2.3 Amps).

So at the max end you have 100aH battery and want to only discharge 50% it would last 11 hours (100 / 4.5 * 50%)

For average this is 21 hours (100 / 2.3 * 50%)

For the 3.3 Amp it is 15 hours.

Doing the reverse and using 12 hour night the drain on the battery as a percentage would be:

Max: 54% drain leaving battery at 46% (4.5 * 12) / 100 as a percentage)
Average: 28% drain battery at 72 %
Spec: 40% drain battery at 60%

Adding all of the other 12V power used at night, you can determine the overall drain and also determine the safety margin you want to have (ie only want to use 30% of battery reserve on average).

Then the day time scenario is that you have to supply the fridge (and other appliances / lights) from the solar and then any current left over is used to charge the batteries. So the solar would need to supply minimum of 2.3 amps (average) up to 4.5 amps (max) at the battery before you would start to charge the batteries.

I am not up to date with solar efficiency but if we use 20% to cover electrical, pointing and weather efficiency plus 12 hours of charging then:

400W of solar would give 400 * 50% / 12V * 12 Hours gives 200 aH, but using average fridge load you are looking at the fridge using 28 aH of that plus any other items running.

Apologies for the long winded response, but hopefully this gives some details if you want to do some calculations. Noting that efficiency factors are generally WAGs (Wild A... Guess) and very dependent on where you are.

Final comment is that as the batteries are then a significant item in make sure the beer is cold, you need to have battery / electrical monitoring that gives you adequate warning that batteries are being depleted. You do not want to get to 9:00 pm and find you need to start the generator.

 

[GUlewis]

Thanks for the feedback guys, I can get three 150w panels fitted to the roof but it's costly. It does come with one 120w as standard so maybe could go an extra two of those if it will be sufficient. The two fridges I can get is either the 140L, which should be sufficient because I've got a 75L car fridge or a 190L which I believe will be far too power hungry.

 

[millers]

Just remember to take into account the 75L car fridge being run from the caravan 12V, when you are camped and not being using the car. Or if you have solar charging car battery as well disregard.

The CRX140 indicates 2.5 Amps (I assume average on the comparison chart) and 7.7 Amps Max on Dometic (Weaco) and 65W average but for AC which would be equivalents to 5.4 Amps DC which seems high. Would assume that this is an inefficiency with transferring between AC and DC.

As the expandas (and most caravans) use a lot of 12V I would check to see if you could run it from 12V all the time and use a single 240V to 12V converter for the whole caravan.

 

[GUlewis]

You make an excellent point there Millers in regard to running my car fridge off the caravan, sometimes depending on where we are the car may not get started for two or three days. I'm not sure whether the system I could get fitted will be enough. I worked it from formulas listed above I could expect 40hrs running for the Crx140 and that's not including the solar input and power draw from everything else.

 

[Smash]

You make an excellent point there Millers in regard to running my car fridge off the caravan, sometimes depending on where we are the car may not get started for two or three days. I'm not sure whether the system I could get fitted will be enough. I worked it from formulas listed above I could expect 40hrs running for the Crx140 and that's not including the solar input and power draw from everything else.

If you have a pop top with air con already I would be very wary of putting that amount of panels it’s bad enough with one you will struggle to push the roof up.

 

[millers]

You can always supplement the roof with portable, for those occasions that you are staying in one place but need to work out a good place to store while traveling. I would also consult as much as possible with people who have run setups like you want and see how they are going. It is one thing to throw calculations around, it is another to have it work.

The good thing with solar on the roof, is that it works while traveling as long as there is no tall objects that can shade the van. Do not know if the TV antenna would reduce or stop a panel (panel dependent).

You may have to consider that the generator for a portion of the day is required (or from monitoring have a specific battery level that you turn it on) so that you do not reach a point that you can not recover from. As well as getting more efficient with LED lighting, better compressor fridges, better solar, the generators are also getting quieter. So your strategy may include a mid-morning top up to help out or a mid afternoon when it is hot enough for some aircon.

 

[Bluey]

Plus very cloudy days means poor power generation or evan rainy days
Whats wrong with the 3 way our 180 litre works a treat

 

[GUlewis]

My experience with three ways is their performance is a little poor in warm to hot weather. I do use a thermometer, so I monitor it all the time. Thought next time I'll give a compressor fridge a go. But I guess either fridge is only as good as its installer. I upgraded the 12v wiring on my current one as they only used what looked like 4mm twin core, the cooling performance improved plus I gain an extra 1.5v at the fridge. Don't want to fit the compressor fridge and then regretting it.

 

[crackacoldie]

I have the 140l Weaco in our van. It has run non stop on 12v since 2013. I have 2@120w solar panels and 2@100aH gel batteries. No complaints at all.

 

[GUlewis]

Thanks for the info there crackacoldie. Have you been off grid for say three or four days and still have plenty in reserves? I do run my car fridge off the van as well.

 

[crackacoldie]

Thanks for the info there crackacoldie. Have you been off grid for say three or four days and still have plenty in reserves? I do run my car fridge off the van as well.

I leave the fridge running at home on battery only, with the solar charging and it has never gone flat. Most we have been of grid for is 7 days with us all in the van and never showed signs of running out of power

 

[GUlewis]

No worries, thanks for the feedback. I think the CRX140 would be big enough for two people, not much smaller than the dometic 150L three way, plus I've got the waeco 75DZ in the car.

 

[rags]

Thanks cracka' your experience is encouraging. We too are considering doing similar however will only be a 110 lt fridge, we only off grid camp so 2x 120a batteries and around 300 watts of solar should see us in business.

 

[Boots in Action]

Have had a compressor fridge in a previous van, but not set up for free camping. Operated from 12V car or 240V connection with auto switchover.

Reason for change was consistent operation, could not get fridge temp right and would loose a lot of food. I think we have this right in the expanda and also use a temperature monitor.

I found a comparison chart here https://www.caravanrvcamping.com.au/caravan-fridge-comparison-chart and I assume that there is a lot of them about.

Taking one as an example Vitrifrigo DP150i Compressor Fridge the figures are:

Max current draw (12V): 3.3 Amps from https://www.vitrifrigofridges.co.uk/dp150ifridge.htm but comparison chart indicates 54W (4.5 Amps) with an average of 28W (2.3 Amps).

So at the max end you have 100aH battery and want to only discharge 50% it would last 11 hours (100 / 4.5 * 50%)

For average this is 21 hours (100 / 2.3 * 50%)

For the 3.3 Amp it is 15 hours.

Doing the reverse and using 12 hour night the drain on the battery as a percentage would be:

Max: 54% drain leaving battery at 46% (4.5 * 12) / 100 as a percentage)
Average: 28% drain battery at 72 %
Spec: 40% drain battery at 60%

Adding all of the other 12V power used at night, you can determine the overall drain and also determine the safety margin you want to have (ie only want to use 30% of battery reserve on average).

Then the day time scenario is that you have to supply the fridge (and other appliances / lights) from the solar and then any current left over is used to charge the batteries. So the solar would need to supply minimum of 2.3 amps (average) up to 4.5 amps (max) at the battery before you would start to charge the batteries.

I am not up to date with solar efficiency but if we use 20% to cover electrical, pointing and weather efficiency plus 12 hours of charging then:

400W of solar would give 400 * 50% / 12V * 12 Hours gives 200 aH, but using average fridge load you are looking at the fridge using 28 aH of that plus any other items running.

Apologies for the long winded response, but hopefully this gives some details if you want to do some calculations. Noting that efficiency factors are generally WAGs (Wild A... Guess) and very dependent on where you are.

Final comment is that as the batteries are then a significant item in make sure the beer is cold, you need to have battery / electrical monitoring that gives you adequate warning that batteries are being depleted. You do not want to get to 9:00 pm and find you need to start the generator.

Hi @millers , some very good technical and mathematically correct figures in your post. However in real life situations, there is no way you would be able to generate anywhere near 200ah from 400w of solar, even in good times. There is very little generation before 9.00am and after 4.00pm, so most generation is between these times and even less if panels are on roof of van and not in optimum positions throughout the day. I recently had occasion to be out off grid for 6 days and on most of these days, it was cloudy or raining for long periods. I was using my 93L Thetford 3 way fridge in temps of 26 to 28 C and very humid too. Connecting a 200w and 180w panel together in series with my MPPT controller, I was unable to meet my daily average usage of 35ah on most occasions. I did connect my auxiliary battery 75ah AGM in parallel with the van battery of 120ah AGM to give me some margin, but was still losing ground for the first few days. Then for a few hours one morning and for some of the afternoon, there was bright sunshine. Even following the sun with moving the panels regularly, I was only able to generate 58ah which was enough to bring my batteries up to "float" stage. At one stage, generation exceeded 21 amps, and was generally in the 15 to 19 amp range for a lot of the time before reducing in the absorption stage and I only had approx 195 ah in batteries to charge. You would be in trouble with battery power and a large compressor fridge in that situation, (just like @Bluey said) not to mention the extra cost and weight to be carried around. My daughter has a 150L ? 3 way fridge in her Jayco Journey and has not had any problems keeping things cool for her two children and husband who likes his beer cold. Expensive decisions if not fully able to handle the differing weather conditions at all times. Just my own humble opinion.

 

[Bluey]

Very well said @Boots in Action

 

[Drover]

Mate who free camps all the time visiting from WA has a compressor job in his New Age with 2 x 120 AGMs, 300w on the roof and a folding 120w (?) and he says at times it will struggle after a few cloudy days and occasionally he pulls the little red power station out, he is contemplating adding another battery just to keep to improve the storage but is concerned with the extra weight as there is not a lot of room to play add another battery and something has to left behind.
if only occasionally free camping or even just going away for a few weeks a year it's not worth the expense.

 

[millers]

@Boots in Action good information. The maths have efficiency figures and time which need to be related to real life and personal use. These values help to determine these.
It is a big decision to go compressor fridge and without a loan fridge, panels wiring etc you need to have some basis to make informed decision.
To be clear the equations are to show an example of the maths and do not represent any specific reality. To make the decision you would need to add your own reality, which comes from those who operate off grid and your estimation of power usage.

 

[millers]

@Drover the other consideration is there is a balance between battery storage, solar generation, usage and the red power station.
The extra battery means more generation is required to top it back up.
You can go longer if you start fully charged, but then need longer to get back to fully charged. So then you need the red power station for longer or more good days.
Individual circumstances will determine but there is a balance between off grid time, battery, solar capacity, usage, genny use and Sun light. To much or bigger in one area may not be efficient and cost you in weight.
The individual circumstances may mean that an extra battery is good as it gives longer timing without having to top up. But you then need more good days or more solar to top up.