I have a folding camper which relies on electric coming from the grey towbar socket when on site with no hookup. The camper does not have a lesuire battery fitted. My car only has single electrics and I don't want to change this.
What I want to do is set up a remote leisure battery and run a positive and negative feed to a grey socket and connect the grey plug lead to that this powering the lights and water pump.
Am I right that I connect the positive feed to pin 2 and the negative feed to pin 4?
You say your car only has single electrics but that's impossible if you use the grey one for power. One for the road lights (black) and one for the power (grey) equals twin electrics or am I missing something?
The car has a single black 7 pin plug which does all the fitted lights ( indicators, brake,tail lights ect). The camper has both black and grey plugs fitted. It's the grey plug on the camper im looking to use once setup on site.
It doesn't have a battery compartment fitted,most likely due to its age. The power for the camper comes via the grey plug from the car battery when set up on site.
What I'm trying to do is use a stand alone battery rather than the car battery.
In your original post you stated that a leisure battery wasn't fitted which sounded like you had a battery compartment but was absent of a battery. Now I fully understand why you require a remote battery but what you need is a wiring diagram for 12S wiring as there are switches and various rated fuses incorporated for overload protection.
Pin number 2 you would need the car ignition 'ON' when requiring power so pin number 4 seems the best choice but I would have thought that you would also need an earth return to create a circuit which is pin number 7 and that is for the functioning of a fridge which is an independent appliance which is obsolete from the circuit.
To be on the safe side I think you need expert advice from a technician on this because deciding which pins to use appears to be rather complex.
You can buy a prewired 12s socket as usually fixed to car towbar & you can connect this to battery. search inside your camper to find the connector block where the cable for your grey 12s plug is connected.
Then from that connector block trace the earth cables & trace cables that feed waterpump & lights. Note the colours of those cables & connect those colour cables from your prewired 12s socket to correct battery terminals. That should work, I would have thought?