13 Pin Wiring

[Mike_S]

Reading through some of the tech pages (644-5 to be exact) in the CC handbook in an idle moment, I realised that there is only one "Ignition controlled power" connection in a 13 pin setup (pin 10). Does this mean that both battery charging and fridge are now running of the same single pin compared to the old 12N/S setup using 2 pins?
Don't seem right to me!!!

Mike

 

[WoodlandsCamper]

I think you'll find:
Pin 9 is battery, return on 13
Pin 10 is fridge, return on 11

 

[Woodentop]

In terms of operation, the 12V supply on pin 9 provides power to the caravan when the car is connected, disconnecting the caravan battery in the process. It only supplies items that would normally be supplied by the caravan battery if the car were not connected - i.e. pumps, lights, radio, 12V socket, aerial amp, oven ignition, heating blower.

When pin 10 comes live (engine running) it supplies the fridge and operates a relay that disconnects the caravan from pin 9 and connects the pin to the battery to charge it.

 

[VicMallows]

I agree that that is the way all modern caravans work. .... BUT WHY?

I really cannot understand the purpose of the so called 'habitation' relay. (It should really be called the non-habitation relay). Why did someone decide that everything in the caravan (except for the 12v circuit to the fridge which is completely separate) needed to be isolated just because the caravan was connected to the car?

That relay is to my mind unnecessary, and itself introduces significant losses into the system due to its inherent resistance.

Yet another issue I have is with the 'master relay' which switches everything ON in the caravan when you switch the master-switch on. This relay consumes an unnecessary 18mA continuously in my case, and again introduces significant resistive losses.

Maybe there are good reasons I have not thought of? ( I approach the issue as an electrical engineer relatively new to caravaning.)

 

[Mike_S]

Thanks for the replies.
The modern system does seem rather over-complicated compared to the older method when a simple double-pole relay switched the battery charging and fridge.

Mike

 

[GD485]

The habitation relay is there to protect the car. I had to rewire a camping trailer and really had to think why the Relay was there.
If you had you caravan on mains hook up and the tow car was connected the charger on the caravan would try to charge the car.
Also if you where on the road ( mains hook up disconnected!) the car would have to supply power to everything on the van you left swtched on.. The habitation relay automatically reduces the loading on the car..
There is a small current needs to power the relay coil but I would hope the voltage drop across the contacts is negligible.

 

[Gafferbill]

Simon Barlow explains things very well.......See Here

He gives a full explanation as to why habitation relays are fitted to modern caravans.
It is all about protecting modern electrical systems now fitted to cars and caravans.

 

[Mike_S]

An interesting article - thanks Gafferbill.

Mike