Minimum voltage for Dometec portable fridge/freezer

[Irish Rover]

I bought a Dometec 40L fridge freezer last year but never really used it. I put some frozen stuff in it 5 days ago and the temp was consistently reading -9C [max setting -10]. I had been motoring a good bit and on shore power at night. I anchored yesterday fairly early and noticed late last night that the power light on the unit was flashing orange and the temperature was rising. I checked my batteries and they were showing 12.68V. By morning the temp had risen to 0C and the voltage was at 12.65V. When the sun came up and the solar panels started producing it started to work again at around 12.75V.
So my questions, technical first - is this power cut-off to save the batteries normal? Can it be set a bit lower? I have a small amount of frozen chicken, a few burger patties, chips and frozen scones in the freezer. I checked after the freezer started up again and all were solid with no sign of thawing. So, are they OK to eat? Finally what temp should I be setting to keep this type of food for a week?

 

[john_morris_uk]

My first thought is that it’s not just the battery voltage that’s important, but what voltage is actually at the freezer. Just because your batteries are at 12.6 v or whatever doesn’t mean that’s what the freezer is seeing.

Our fridge freezer compressor doesn’t auto-cut off until the voltage drops to 11.7 v IIRC. (It’s never happened so I can’t speak from experience, only from my memory of the specification.).
.

 

[john_morris_uk]

What have you got the battery protection setting to? I see from the instructions that if you’ve got it set to high it starts to limit its functions at 12.6 lots. If it’s low you’ve got until the battery drops to 11.6 if I read the table correctly. https://www.dometic.com/assets/66/86/dometiccfx3_opm_4445103159_apac(en)_2020-09-09_76686.pdf

 

[Irish Rover]

OK - pardon me. It's a Mobicool not Dometec [I knew this and why I wrote Dometec is beyond me ]. I can't see any reference to a power cut off in the manual but I suspect your first observation is the key - I'll check the voltage at the cigarette lighter type socket and replace the cable if necessary.

 

[vas]

IR, if you can do check the voltage at the device. If the cable to the "lighter socket" or whatever you have the fridge hooked to is light gauge and 4-5m long, voltage drop in there could be substantial. Adding an extra 1m or so of not so thick cable to the fridge, here goes .5V+ from the victron battery monitor value you see...
fridge could well be sucking 4-6A (if not more) on thin cables that's a disaster!

 

[ChromeDome]

Can be downloaded from Mobilcool (btw same as Dometic)

 

[Irish Rover]

Victron Connect showing batteries 14.05V and input to unit is showing 13.70V so hardly critical. Going to check out now, @ChromeDome. Thanks

 

[Irish Rover]

View attachment 157839

Can be downloaded from Mobilcool (btw same as Dometic)

I found that, thank you. It was set to High so I've reset to medium and we'll see what happens tonight. Thanks all.

 

[geem]

Almost certainly volt drop. I had a similar problem on my 40 litre plug in fridge until I uprated the cable and installed a proper power socket not the rubbish cig lighter that it came with

 

[vas]

Victron Connect showing batteries 14.05V and input to unit is showing 13.70V so hardly critical. Going to check out now, @ChromeDome. Thanks

what does "input to unit" mean IR? the terminals in the actual coolbox or the cigarette lighter socket?
Looks like you have enough voltage drop to move the switch straight to LOW imho.

 

[Irish Rover]

The unit end of the supplied cable which has a female socket that connects to the male on the unit itself. I'll see how it goes tonight after changing to medium and change down if necessary. Thanks.

 

[WoodyP]

I have a 25 litre Dometiq cold box which wouldn't work until I gave it its own dedicated supply to eliminate voltage drop, to which they are very sensitive.

 

[ChromeDome]

My Mobicool 40 Fridge is mainly used in the car (trips, outings, shopping etc.).

Connected to the lighter plug it is powered when driving plus some 15 minutes (designed to keep GPS and stuff alive during short stops).

To mitigate the battery monitor shut off I've added a deep cycle battery that runs the fridge all day regardless of standing and is charged by the car. Works perfectly between longer drives when it gets charged fully.

Now and then give it a proper charge at home with the Noco 26A charger. Lovely to have proper cooling during the day (on a hot day beer can't get too cold 'eh?)

 

[Irish Rover]

what does "input to unit" mean IR? the terminals in the actual coolbox or the cigarette lighter socket?
Looks like you have enough voltage drop to move the switch straight to LOW imho.

Had to move to low just now with Victron showing 12.85V.

 

[geem]

Had to move to low just now with Victron showing 12.85V.

That's a vo,t drop problem for sure

 

[Irish Rover]

That's a vo,t drop problem for sure

A bit sloppy where I'm anchored tonight to go checking again and a cold beer screaming at me - I'll check more fully when I can.

 

[vas]

you're lucky weather is still crap and rather cool. If it was a nice 35C you'd be happy to have lukewarm beer now in Mykonos or wherever you are round there
on a serious note, try to get some THICK gauge cables straight from the el.panel to where you want to fit the cooler. You seem to have over 1V drop which is a lot at circa 6A consumption.

 

[Irish Rover]

you're lucky weather is still crap and rather cool. If it was a nice 35C you'd be happy to have lukewarm beer now in Mykonos or wherever you are round there
on a serious note, try to get some THICK gauge cables straight from the el.panel to where you want to fit the cooler. You seem to have over 1V drop which is a lot at circa 6A consumption.

Thanks again. Rough crossing from Ikaria this morning and now anchored in a bay in SE Mykonos.
Failed again last night on the lowest setting. I'll be I'm Syros tomorrow and I'll buy good cable and change it. I'll also connect direct to the supplied cable to cut out the cigarette lighter socket. For now it's running off the inverter.

 

[ChromeDome]

If you have a spare battery you can make a quick fix temporarily by putting it (in parallel) in front of the fridge - as an electric buffer.

Power source -> buffer battery -> fridge

 

[Irish Rover]

If you have a spare battery you can make a quick fix temporarily by putting it (in parallel) in front of the fridge - as an electric buffer.

Power source -> buffer battery -> fridge

Thanks. The inverter is working fine. I just don't have a 220 socket in the area where I have the freezer so the extension lead is a bit messy. I'm solo at the moment so I just want to get it sorted before my wife and daughter join me on Saturday. Putting a 220v socket in that area is a job on the list for when I get back to home port.