Advice on wiring from Car to Van

Submitted: Friday, Feb 28, 2014 at 09:01
ThreadID: 106455 Views:1687 Replies:4 FollowUps:3
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I'm after some advice on connecting a new van I am about to pickup.

I have a Prado with 2nd battery and isolator, with a 7 pin flat plug and an Anderson plug connected to the 2nd battery.

On the van I am about to pick up, there was a 12 pin plug. They are changing that to a 7pin plus an Anderson plug. The van dealership asked me if I have power to pin 2 on the 7 pin plug - apparently needed to power the fridge during driving.

I thought the Anderson plug would go to the dual batteries in the van, which in turn will power the fridge during driving, therefore I don't need pin 2 on the 7 pin to have power.

Can anyone confirm this - or help me out with a suitable solution??

thanks for any help

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Reply By: Ross M - Friday, Feb 28, 2014 at 09:36

Friday, Feb 28, 2014 at 09:36
The Anderson plug to the van fridge is what will run the fridge ok.

Pin 2 on the 7pin plug hasn't got the capacity to run a compressor fridge properly let alone a heater element absorption type fridge.

Even if there is 12v power to pin 2 it isn't much use apart from maybe powering lights in the van.
You don't want pin 2 connected to the fridge/s in anyway.

If a 3 way fridge then the Anderson or it's circuit will have to be disconnected to stop the battery going flat. You probably have that usage protocol under control anyway.

The caravan dealer should realize if you have an Anderson you likely won't be using pin 2 at all.
The Dealer himself may not be switched on or perhaps operating on less than full voltage.
AnswerID: 527382

Follow Up By: Holty - Friday, Feb 28, 2014 at 09:50

Friday, Feb 28, 2014 at 09:50
thanks Ross,

The only time I'll have the Anderson plug connected is during driving to keep the fridge cool.

My limited understanding is that during driving it'll be fine and continue to charge away - sending charge to the batteries in the van as well which will drive the fridge?

My real lack of understanding is does the Anderson plug on the van connect directly to the fridge - therefore just running it and providing no charge to the batteries in the van, or does it go via the batteries - or to both fridge and batteries?
FollowupID: 809786

Follow Up By: Member - John and Val - Friday, Feb 28, 2014 at 16:16

Friday, Feb 28, 2014 at 16:16

We are assuming it's a 3 way fridge - if it's a compressor fridge then it won't be so demanding on 12V from the vehicle and some of what's been said here will be less important.

As said, it is important not to allow your van batteries to power a 3 way. It is ok to run it from the alternator while driving, using the anderson plug setup. This then means that if the batteries were sharing that line for charging then the fridge would need to be disconnected from the alternator (=batteries) line when you stop. This disconnecting could be done automatically using a trembler switch.

There is another issue that shouldn't be overlooked. The 3 way fridge draws considerable current on 12V, typically 12-15 amps, which will result in a significant voltage drop due to resistance in the wiring. This loss of alternator voltage will severely limit your ability to charge the batteries. Two options - I use two anderson plugs, one feeding the fridge and a completely separate plug and wiring for battery charging. Even this may not be adequate where there a long runs of cable, or if the cable is too light. The other option is to use a dc-dc charger to take what voltage is available and increase it so as to deliver a full charge to the batteries. (The mention of dc-dc chargers on this forum is like waving a red flag at aggressive bulls, but they do have a place and this is one of them!) There are some considerations with dc-dc chargers - notably can your alternator supply the required current for an extended period? (These chargers draw extra current (amps) in order to generate the higher voltage required to fully charge your batteries.)

The above assumes that yours is a 3 way fridge ( ie can run on gas). If it's not, then the electrical demand is far less.

You may find Electricity for Camping a useful read.


J and V
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FollowupID: 809797

Reply By: Rustynails59 - Friday, Feb 28, 2014 at 10:13

Friday, Feb 28, 2014 at 10:13
Hi there, i am picking up a new van this month too
If your van has ESC brakes, you will need a seperate anderson plug thats connected to main battery
accesories for caravan can be connected via anderson plug connected to auxillary battery
i guess it depends how its wired but i would have thought your anderson plug could do the fridge- need speak to manufacturer
7 flat pins will fit into 12 pin (not other way around)
AnswerID: 527390

Reply By: Dennis Ellery - Friday, Feb 28, 2014 at 14:57

Friday, Feb 28, 2014 at 14:57
Hi Hotly,
3 way fridges in caravans shouldn’t be connected to your caravan battery.
If the van is wired correctly - the fridge should be on a separate circuit, run from the car's alternator or battery.
If your Anderson plug charges the van battery it shouldn't be connected to the fridge.
AnswerID: 527401

Reply By: bks - Friday, Feb 28, 2014 at 19:55

Friday, Feb 28, 2014 at 19:55
Slightly of topic but hope someone can help. I am installing a cable in the 4wd to power the soon to arrive Camper trailer. I have no problem with everything except how to install the Anderson plug to the back if the 4wd. Is there some sort of bracket that will attach the plug to the towbar? As the plugs are plastic I cant figure out how to permanently attach it.

Any photos would be appreciated.
AnswerID: 527421

Follow Up By: Member - Stinger2 - Friday, Feb 28, 2014 at 21:42

Friday, Feb 28, 2014 at 21:42
Hi bks, your anderson plug should have 2 hole drilled through it, just bolt it up to the cowling on the back of your 4wd, or attach it to your towbar..
FollowupID: 809823

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