I have recently purchased a fifth wheel outfit, but the leisure batteries do not seem to be charged from the donkey. The cart has a huge solar panel on the roof but I would like to have the convenience of charging from the Ford Wildtrak. There are 2 12 volt sockets in the truck, one for the cart lights and one for the electric brakes. Which socket would be best to feed the split charge relay from and what pin should it go on. It is only for the charging relay as the fridge is only 2 way, so would be on gas when on the move.