Best way to run a 3 way fridge from a tow vehicle whilst driving.

Has the tow vehicle been wired with 2 Anderson plugs? If so why can't you run things from the two Anderson plugs as is?

G'day

This might be opening a can of worms, but I have a mate who runs his 3-way fridge in his caravan ON GAS WHILE DRIVING. He reckons he's been told that this is OK by a caravan expert. What does everyone think of this?

Bill

I wouldn't do either !!

Either piggy back both andersons straight to the 4wd anderson and pull the fridge one when you stop driving or do the same but put a vsr in the fridge line.

Why would you want a dc/dc charger powering a fridge ?? or an inverter ??

Keep it simple !!

Ben,

Looking at the M300 Owners Manual, it appears this charger does not have a supply mode. Therefore it is not suitable to run the fridge unless both are connected to the battery. Additionally, trying to charge a battery with a high-drain appliance like a 3-way fridge (12-15 amps) connected at the same time is not very satisfactory. So installing an inverter to run the M300 is not the way to go in my opinion.

Given the two Andersons on the camper, if I was doing it this is what I would do: I would install an Anderson at the back of the tug, and make or buy an Anderson double adapter to power the two Andersons to your trailer. I think the best way to charge a camper or caravan battery is with a DC-DC charger located in the camper near the target battery. The DC-DC charger can make up for the voltage drop encountered in the long cabling from the alternator and still provide a tailored charge to suit your camper battery.

So one trailer Anderson would power the DC-DC charger. Depending on the output of the DC-DC charger the supply cabling in the trailer for that should be 6mm, but preferably 8 B&S. I assume the other trailer Anderson that goes to the fridge goes directly to the fridge's 12V input.
Check the cabling - it must be AT LEAST 8 B&S (=8AWG, =8 gauge. NOT 8mm). If it is not, then re-wire it.

This is because for the fridge to work on 12V the 12V supply MUST have minimum voltage drop under load and the only way to do that is with big cable. You need 12V or more UNDER LOAD at the fridge. Small cable won't hack it. You need an Anderson at the back of your vehicle. That must be cabled with AT LEAST 6 B&S for the reason stated above - ie to minimise voltage drop in the supply to the fridge. You should also use an isolator of some kind (VSR or ignition-controlled "dumb" solenoid) so that when the engine is off the supply to the camper is off. This will prevent the fridge running your crank battery flat when you go to buy your supplies.

Yes, you could just unplug things, but the first time you forget you will rue the day you decided to skimp. Make up or buy an Anderson double adapter so that you can plug it into the back of the car and have two Anderson outlets.
One will go to the fridge, the other to the rest of the camper and the DC-DC charger. If you make your own Ando double adapter, for practical reasons use 8 B&S (it's only a short cable run, maybe just a few inches, up to you), the 6 is too hard to do tight bends and you won't get two cables into one terminal.
(See the photos to get an idea of what I mean.)

As others have mentioned, you can get Ford to de-activate the Ranger's smart (ie low output) charging system. This would definitely be better for the fridge and would be my recommendation for practicality and simplicity. Also mentioned elsewhere, Redarc make low voltage versions of their DC-DC chargers for vehicles like the Ranger, so you could try an unmodified charging system. If it works, well and good. If it doesn't, get it switched off.

Cheers

Ben,
I have a new Ranger and don't have any off the bits mentioned.

First thing I did is have the alternator smart charge turned off by Ford. They do this for free. Then get your heavy duty wiring installed for the anderson plug and when you pull up just pull the plug out so the fridge doesn't flatten your start battery. I then just change it over to gas.

That is all I have and all works well with no expensive chargers or relays.

One thing I won't do is ever run a fridge on gas while driving.

I believe the smart charge function in the Ford ranger can be turned off by the dealer, if you get this done then you could go with a simple VSR setup if you prefer.

Ben,

Bearing in mind that a 3 way fridge draws in the order of 12 amps or more, the 12 volt setting should only be used when the engine is running and switched through the ignition circuit to ensure that there is no current draw from both the vehicle battery, or the one in the camper.
When parked up for a shortish time, the fridge will maintain the temperature as the door is not being opened.

Running the fridge on 12 volts from the camper battery will do nothing but destroy the battery in a short time, and using an inverter for a current draw as large as this, doesn't make sense. Don't even consider running the fridge from a 12 volt supply for any length of time. If stopped for a prolonged period, switch the fridge over to gas. This is the most efficient for this kind of fridge, unless you have an external 240v supply.

My best recommendation is to sell the three way fridge and invest in an upright compressor fridge. These are much more efficient and much more effective in warmer climates.

OK, I thought that I'd get reactions like that. I'd like to see the one the poor old moderator had to remove.

I'll now get my mate, who will remain anonymous, to look at this, especially the great photo from Bob Y.

In defence of my mate, he did say that he would always turn the gas off before going into a servo.

I might also mention that the 2 AGM batteries in my van are only charged from the solar panels on the roof. The towing Isuzu ute is not wired for van charging. The van fridge is a compressor type (ie not a 3-way - only draws 4 amps, as compared to 10 to 15 amps for the average 3-way fridge) and we've not run out of power yet. Perhaps we'll get into trouble if we get a run of cloudy days, but so far so good. Not much use to you, Ben, as you're already wired up, but this might prove to be a real and simpler alternative for others now that solar panels are so cheap.

Cheers

Bill