Caravan Fridge Wiring

Submitted: Sunday, Feb 08, 2009 at 00:14
ThreadID: 65789 Views:30364 Replies:12 FollowUps:3
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Curious to know how people have their caravan fridges wired where the van has it's own battery. 12v of course.

When I leave home I have my van battery fully charged and fridge running on 12v whilst travelling. When I get to my destination the battery in the van is dead, so the fridge must be drawing from this as I travel. Car is wired up with 12 pin Anderson plug and intended that van battery would be charging as I went but charge to van battery appears insufficient to match fridge draw down..

Something is not right here. How do other people have their fridges wired. My neighbor has his wired straight to the car in parallel with the car battery and must turn the fridge off every time he stops to avoid flattening the car battery. His does not run off the van battery at all.

What is the norm and how should it be set up for optimum power use conservation. When I get to camp of course I put my fridge on gas or AC power if in a caravan park.


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Reply By: Matt(WA) - Sunday, Feb 08, 2009 at 02:04

Sunday, Feb 08, 2009 at 02:04

Your 3 way fridge on 12 volt can draw up to 10amps or more. There is no way through your hot wire through a 12 pin plug will supply nearly enough amps.

I can recommend two things:
1. Get a compressor fridge in your can which will use a lot less power and be more effiecent, cool your food quicker and also work when its hot.

2. Up grade your wiring to your van. I would recomend some heavy duty cable connected via anderson plugs directly from you batery(2nd battery if you have one)

I have done both of these and have gotten rid of my fridge dramas

Hope this helps.


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AnswerID: 348092

Reply By: Rockape - Sunday, Feb 08, 2009 at 09:01

Sunday, Feb 08, 2009 at 09:01

I have 10 square mm flex (welding flex) running back to an anderson plug and then to the van battery. The cable is protected by circuit breakers at both ends. I don't worry about drain when I stop as we only pull up for a max of 2hrs. A blocking diode in the van stops the vehicle trying to use the van deep cycle battery on start up.

Have toyed with putting in a compressor fridge, maybe will one day. Dollars

Have a good one
AnswerID: 348100

Reply By: ABR - SIDEWINDER - Sunday, Feb 08, 2009 at 09:09

Sunday, Feb 08, 2009 at 09:09
Hi Jeff

12 Pin Plug

Anderson Plug


I recommend 2 circuits from the tow car. One to charge the van battery and one to power the fridge directly off the starter battery via an ignition activated relay or solenoid. 6 B&S to charge the battery and 6mm2 to power the fridge. (Minimum)

There are also Fridge-Switches available that are automatic.


AnswerID: 348102

Reply By: DIO - Sunday, Feb 08, 2009 at 09:19

Sunday, Feb 08, 2009 at 09:19
It appears that you might be a bit confused as to what an Anderson Plug is. Accompanying piccy shows one half - for your info. Anderson Plug
AnswerID: 348105

Reply By: glids - Sunday, Feb 08, 2009 at 09:21

Sunday, Feb 08, 2009 at 09:21
Hi there Mildew,

When travelling, I power the fridge from the vehicle battery using the following:
*'Fridge' switch _Affordable_Storage_Drawers.aspx from ignition switch so can only draw power when engine is running or ign switch is in run position.
*from 'Fridge' switch, live wire goes to the coil of a 30A relay, which is connected to vehicle battery with 30A fuse.
*wiring from relay to rear of vehicle is 8B&S gauge, for both +ve and -ve wires, connecting to 50A Anderson plug
*wiring on van from Anderson plug to fridge is also 8B&S, +ve and -ve wires.

Short stops are not a problem, fridge will keep cold. If we are going to stop for a longer time, or weather is really hot, I would run the fridge on gas. Our fridge cannot draw from the 'van battery.

As others have noted, you need heavy wiring for running fridge or charging van battery from vehicle.

AnswerID: 348106

Reply By: Member - Doug T (NT) - Sunday, Feb 08, 2009 at 09:38

Sunday, Feb 08, 2009 at 09:38
Both my Fridge and freezer (Westinghouse), both the same size run on 240v only, when I move on to another location and they are disconnected from the power they last all day until in re-connected to power, everything in the freezer is still frozen solid and fridge has kept everything in it cold all day, so if your staying in Caravan parks each night I don't see any reason why you need to run the fridge while on the move,

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AnswerID: 348111

Reply By: Member - Toolman (VIC) - Sunday, Feb 08, 2009 at 09:39

Sunday, Feb 08, 2009 at 09:39
My Caravan fridge is wired to run on 12 volts drawn from my vehicle, not from the caravan battery. Without being attached to either 240 volt power or to the vehicle, the fridge runs on gas. I suspect this is a standard wiring set-up for most caravans as that's how I bought my van and I made no special requests regarding the fridge wiring.

The only thing I did was to wire the No 2 pin of my trailer plug (7 pin round) on the vehicle, to run the 12 volts from my auxiliary battery. The plug on the caravan which was already wired that way.

AnswerID: 348112

Reply By: Ray - Sunday, Feb 08, 2009 at 09:49

Sunday, Feb 08, 2009 at 09:49
I have brought up this subject before. I run my Electrolux fridge off 150 amp hr batteries that are on the caravan but there is an isolator fitted so that the batteries are isolated from the fridge when the ignition is turn off. The batteries on the caravan are charged from the car with 16mm2 cable via a 175 amp Anderson plug. The isolator is operated through a large standard 7 pin plug.
AnswerID: 348113

Follow Up By: GerryP - Sunday, Feb 08, 2009 at 11:34

Sunday, Feb 08, 2009 at 11:34
My set up is somewhat similar to yours Ray and works fine. Caravan batteries charge via Anderson plug from the car and the fridge runs off the van batteries while traveling. I have upgraded the wires from the batteries to the fridge as they were way undersized. Only difference to Ray's setup is that I use one of those Fridge Switch isolators shown in Derek's response above. I must say the Fridge Switch works really well - it is a movement sensor and automatically isolates the circuit to the fridge after you have stopped the vehicle for a couple of minutes.

FollowupID: 616349

Reply By: mildew - Sunday, Feb 08, 2009 at 10:00

Sunday, Feb 08, 2009 at 10:00
Thanks for the replies people and for clearing up my confusion about the Anderson plug. It is definitely a 12 pin plug I have. The Auto Electrician who installed it told me he only installs so that when I turn off my ignition the fridge goes off in terms of drawing power from the car but obviously it is continuing to draw from the caravan battery as the volt meter in the van drops rapidly over about an hour or so to nothing. So I need to get this sorted so that the fridge doesn't draw from the van battery first. As to how the car is wired, I guess I will have to get this checked out too. Sounds like a heavy wire straight from the car battery is the go with an automatic cut out switch or motion detector switch so that it stops drawing power when the car is switched off.

More work to do.
AnswerID: 348117

Follow Up By: Member - Mike DID - Sunday, Feb 15, 2009 at 16:01

Sunday, Feb 15, 2009 at 16:01
It sounds like your battery is already damaged from being over-discharged.
FollowupID: 617434

Reply By: snailbait (Blue mntns) - Sunday, Feb 08, 2009 at 10:17

Sunday, Feb 08, 2009 at 10:17
Hi all
A solution to some battery problems but not all it to travel with the parking lights on.
This helps when the starting battery is fully charged and the alternater goes to sleep and only alows a trickle charge to the second battery and the the battery in the caravan.

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AnswerID: 348122

Follow Up By: DIO - Sunday, Feb 08, 2009 at 17:52

Sunday, Feb 08, 2009 at 17:52
It's illegal to drive with parking lights on. Use headlights, much safer and very legal and will also maintain a good charging rate.
FollowupID: 616410

Reply By: bob&loz - Sunday, Feb 08, 2009 at 12:45

Sunday, Feb 08, 2009 at 12:45
Hi Jeff
All good advice above but remember that when you sort it all out you will need to buy a new battery, as the one you have will already be stuffed from being flattened a few times.
AnswerID: 348145

Reply By: Wahroonga Farm - Sunday, Feb 15, 2009 at 12:14

Sunday, Feb 15, 2009 at 12:14
The problem is voltage drop due to cable resistance. This is a problem no matter how massive you make the wiring from alternator to van.

It is cheaper and simpler to overcome this problem by electronic means.

1. Use a 300w modified sinewave inverter to power the fridge via 240v. This is an excellent solution for older vans with 2 way absorption fridges (ie no 12volt). The inverter will operate with an input voltage down to about 10.5volts. 6mm cable from car alternator to the van mounted inverter via an Anderson plug or similar will do the job. Ensure the cable is protected by a 30A fuse or breaker at the car battery/alternator. Keep it simple in the van with the inverter powering only the fridge via the fridge power cord. This will require around 150-200watts, so don't operate it when the vehicle is stopped for more than a fuel stop..

There's even a few spare inverter watts to run an 8A x 240/12 inverter charger for a house battery. But this is getting a bit more complicated.

2. If you stay with 12v for the fridge, then use a 12v booster and 6mm wiring as described above. Leab make one. I'm sure there's others.

All about keeping away from massive cabling, which may become a real fire hazard in an accident.
AnswerID: 349169

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