Relay for 12Volt camper fridge

Dear 12volt I plan to install a relay and wiring from my vehicle battery through to a camper trailer which holds a 12 volt camping fridge. The fridge has two dual deep cycle batteries connected in series, and the plan is to 'charge' these batteries as I drive. A store assistant recommended 50amp wiring and relay from vehicle to trailer as insurance against burning out wiring should my fridge batteries run flat when I reconnect car and trailer. As I understand it, once I turn off my ignition, I automatically disconnect car from trailer batteries which is desirable to avoid draining my car battery. The assistant also recommended I consider installing a solenoid as part of the wiring system. I'm not sure whether this is necessary. Could you help with a wiring diagram for the relay, and also comment on the solenoid suggestion? If you recommend I install a solenoid, could you also provide a wiring diagram for that too please. cheers

The relay and the solenoid would be redundant. A continuous duty solenoid would probably be the best, but I think a 30A relay would work fine also. Wiring is going to be pretty easy for this... Using 30A 'Bosch' relay 30-Car Battery 85-Ground 86-Trigger- from fuse-box, on with ignition 87-to trailer batteries

That sounds simple enough even for me! What is your view about the recommendation I go for 50amp wiring? The existing wiring I have is 15 amp, and I have been advised that I risk burning out wiring if my fridge batteries are dead and my vehicle cranks high amps on start up. cheers

#1- deep cycle batteries should not be run down to less than 50% charge. #2- I don't think you would need to run wiring for 50A. A good place to go for this information is the RV forums located here

Dear FF Thanks for the tip and the link. cheers

Thanks for the diagram John. I presume it makes no difference that I have my second battery in the trailer, and not in the engine bay?

As long as the wire is connected the battery will charge.John DeRosa (Hotwaterwizard)

Stockton California

When in doubt, try it out !