Powering compressor fridges

[Philip M]

While I am awaiting parts which I hope are going to fix a particularly elusive fault on my existing three way fridge, my mind has been increasingly turning to the idea of replacing it altogether with a 12 volt compressor fridge. 

I've been looking at Just Kampers JKF50 which would fit easily into the existing cabinetry and only uses 0.7Ah at 25 degrees ambient temperature once cold and set to eco mode. That would use approx. 17Ah in a 24 hour period.

I was wondering if anyone here has any experience of running a compressor fridge and what power I might need to comfortably power it off-grid for a week.

I have an Eriba 320 poptop van with a 115Ah battery which gives me a usable 57Ah, and I would need to upgrade my portable solar panels. I have insufficient space to fit them on the van, plus I'm very tight for weight. 

From my experience of the 40W panels that I already have, I know I can expect around 15 to 75% of their rated value depending on the weather plus electrical losses. 

I use very little battery power as there is no TV or shower and all lights are LED. 

Anyone have any thoughts as to the minimum size panel I could get by with?

[hja]

I dont know about the model you are looking at but i can tell you about our compressor fridge. Ours is a Dometic undercounter fridge with freezer box. We had a 95ah battery and 120w solar on the roof. Other battery pull is pump, lights, ipad & phone charge. Arrived at site with full battery. Two nights on the site, no hook up. Didnt take van off site. Rained most of the day so no solar. By morning after second night battery was down to 12v. Regained its power as soon as we drove, but obviously not what we wanted. We swapped to lithium and a new solar controller. We have now done four nights without moving van, but we did have solar. We are unlikely to stop any where longer than that without moving.

[Philip M]

Thanks for your reply, it's very helpful to hear real experience about these devices. Your set up sounds about the same as mine. In theory a 95Ah battery ought to provide a useful 47Ah which, if the fridge drew 1Ah on average, two days sounds about right. I'm encouraged that your new set up works well though. What's the size of your lithium battery?

[hja]

230ah. We could have had a 100ah lithium which would have given us more power than the original battery because of being able to run it down more.  However, we had our system installed for us and there wasnt much difference in the overall cost of installing the bigger battery. So more power, within reason, cant be a bad thing, so went for the bigger battery. Still fits under the front passenger seat, and still lighter than original battery.

[Philip M]

That is considerably more useable power than the lead acid. The charger in my van is a Sargent PX-300 smart charger which charges at a maximum of 20 amps at 14.4 volts. Looking at the specification it is for flooded and AGM batteries, but I wonder if it work and be safe with a lithium battery. Anyone tried this combination?

[Puddlejumper]

We had a compressor fridge in our old motorhome and will be changing our current three way this winter with another compressor fridge. Our experience was really positive, they keep stuff consistently cool irrespective of ambient temperature, they don’t get all moody if you’re not level and they don’t use any gas when off grid. In comparison this year with our new van we’ve already gone through x5 6kg gas bottles as we’re almost always off grid. With the old van we would maybe use x2 a year. Electricity consumption was pretty low, with our solar set up (200W roof mounted) it would keep the fridge going during the day with no real draw on the leisure batteries. Current draw was around 2-3A when compressor was running which was around 40% of the time so realistically it would draw around 1.5Ah per hour, we would see something like 10Ah being taken overnight but the solar would have us topped back up by 10am on a bright day. 
The only downside was it was noisier than the 3 way but not particularly noticeable, I slept with my head next to the cabinet where the fridge was and it never disturbed me. I also had to wire it so it ran directly from the battery via a fused and switchable spur so it would run while we were driving but the plus was I got rid of the relay.

Hope this helps