Advice on 3 - way fridge running on 12v

It's a fact that 3 way fridges are not very good when travelling especially in hilly areas and yes they do not maintain a CONSISTANT temp when travelling because they need to be level to operate efficiently. Upgrading the wiring won't usually help I've tried that one. You just get use to it especially in hot weather when I use to stop for fuel or site seeing I ran it on gas. 3 ways just can't compete with 2 way compressor fridges they don't perform very well on hot days the are very very power hungry you will get approx less than 2 hours out of a battery then it needs charging and about 2 to 3 days out of the same battery with a 2 way compressor fridge and they will operate up to a 30deg angle so travelling doesn't worry them and they are cheaper to buy. If I ever get another van I would replace the 3 way with a Waeco Coolmatic upright set up dual batteries and solar panels with a batt monitor and have trouble free touring and only use gas for cooking.

Yes, the 12v operation is only to maintain fridge temperature while travelling.
Trying to maintain the freezer temperature is probably beyond the physics of 12v operation.

As far as the van battery is concerned, you may need the inclusion of a dc-dc charger at the van end to boost any voltage drop back to what is required to charge the battery from the vehicle alternator.

Keep in mind, the 3-way fridges running on 12 volts consume a lot of current and prolonged stoppages during the day will not do much except drain the battery.

The best solution is to add the dc-dc charger, then replace the Dometic fridge with an upright compressor fridge that runs on 240vac or 12vdc. Both Waeco and Engel have upright models available. If you have a dc-dc charger with a solar input port (such as the Ctek D250S dual), you can maintain a charge in the battery at camp.

From our experience it is always worth checking that the fridge has been properly installed with sufficient insulation packed in around it. It made a huge difference to the fridge in our previous van which had your problem when proper insulation was installed and the baffles adjusted. Our current properly installed 3way fridge travels well even for a long day. In hot weather we turn it to gas when we stop for lunch etc. Is yours a T Rated fridge suited to hot weather? Lynne

Hi Paul,

We had a 3-way in a new Avan camper. It never worked very well on 12V because the wiring in both the tow vehicle (done ny an auto sparkie) and the van (done by the factory) were simply inadequate.

We fixed it by installing an isolator in the tow vehicle and heavy wiring (6B&S) from the battery to the isolator and then to an Anderson at the rear of the tow vehicle.

We also installed 6B&S wiring from the Anderson on the van to a DC-DC charger for the van battery.

We installed a relay so that when the tow vehicle was running the 12V to the fridge came from the tow vehicle, and when stopped it automatically switched over to the van battery.

We upgraded the cabling in the van from the battery and the relay to the fridge. From memory we used 8B&S for that as they were short runs.

After that it worked quite well on 12V - not as good as 240 or gas, but as well as it was ever going to work on 12V.

Cheers

You could bypass the battery and take power direct from the tow vehicle via the Anderson plug or fit a DC - DC charger.
Google 'Fridge Switch' as they're easy to install and work very well. They're a motioon detector switch that fits at the bottom rear of the fridge and only supplies power when the van is moving.
Also don't expect a 2350 fridge to work well in hot weather not matter how well its installed or insulated as it only has a 'ST'climate rating.
Ozjohn.

Thanks all for sharing your experiences and advice. A compressor fridge sounds better but I'll have to stick to the 3-way a bit longer because of the cost. Will check out the insulation, wiring and look at the DC-DC charger.

We had a 2010 Swan Outback as well, best advice is dump the 3 way and get the upright Engel 2 way which is same size and slots straight in. You can run it whilst driving and drawers low amps and hold regular temp! We also had same fridge in our Ultimate Camper.

David

Hi paul.
This is a option for you.i have done this to my fridge both in the jayco stirling when had it and now in the lotus trooper.we are by the sounds like you.when hitting the black top travel a good days.nearly every1 who says there 3way fridge works fine on 12v are normaly traveln for a few hours aday.not saying all here.down in the south its cooler threw winter so any fridge is going to work.up north here bit different.
Even when we brought the jayco the sales person told us that the fridge runs on %20 efficent.
What we have done is run anderson straight off my 2nd and 3rd battery and installed a inverter mounted up behind the fridge threw a fuse and rcd.so now when traveling fridge is running on 240.keeps everything nice and chilled even after a 10hr day drive up in the top end.when pull up then flick over to gas.if you read specs the fridge pulls round 140 watts so i just run a small 300 watt inverter.
Food for thought and my 2 cents worth

Paul makes a valid point and spot on about the efficiency on 12v , the other option is 2 way fridge suggested above or is it practical to keep as is running 12v in conjunction with Techni Ice? If 12v whilst travelling is the issue why not put some frozen Techni ice sheets in until you arrive? Just thinking out aloud as this may not be practical?

The problem is that with a 12V supply to the heating element in the fridge it is only necessary to loose (say) 1V and 8% of the energy is lost and that's easy to do in a circuit carrying 12A+. In reality it's worse than this because they don't work very well at just 12V anyway.

The solution is to purchase a small inverter - 300W will be fine - and non sine wave is OK too (but I'd go sine wave 'cause they're cheap these days) and run the fridge from its 240V heating element.

Otherwise three-way fridges are an excellent choice for people who camp in one spot for a number of days, as do I

And... before the, lacking in knowledge, doom-sayers rush to their keyboards to issue dire warnings of the evils of 240V in a vehicle.. I refer you to a thread I engaged in on this site about 12 months ago.

NM

HI Paul
The essentials for best operation of a 3way are:
[1]Adequate wiring from the TUG battery ALL THE WAY to the fridge with NOTHING else on that circuit
You require the design voltage for them to generate the necessary heat in the boiler
THAT means you require MIN 12V at the fridge terminals WITH THE FRIDGE RUNNING
& the vehicle alternator inputting to the crank battery [medium idle speed]
If you are not getting at least 12V, the CABLES ARE undersized[as usual]
['2]the fridge does draw a high current & should only be on when the engine is running
This can be achieved by either a "Fridg Switch"[motion sensor]or an ignition controlled relay switching the POS line to the fridge.
[3] Very few 3WAYs are installed to the fridg maker's instructions
This particularly includes the ventilation a baffling at the rear to get the best possible cooling air flow through the fridge CONDENSER

If you do a bit of MR GOOGLE search for "3way fridge fans " "3way fridge baffles"
& similar you will see loads of proven methods,
or come back here & I will give more lengthy details
[4]The charging circuit to the VAN house batteries should be an entirely SEPARATE circuit from the tug battery,to achieve BEST charging of the house batteries


[5]A compressor fridge is great IF you have the means of keeping the batteries charged

That needs a lot of consideration & just how much Solar &/or battery capacity you will need depends on your camping style & fridge temp settings
then you have to decide what you would do if a run of overcast /rainy days set in & you got little solar input
But IF you only used powered sites then a comprressor fridge would be excellent

I myself have both & although I have 200W of solar & 200Ahrs battery capacity
I am often glad I have a 3way
Give it a lot of thought !!
PeterQ
electrician