I would like to run the 12 volt capability of my 3-way caravan fridge whilst travelling rather than the gas. If I put a 12 volt battery in the caravan what system do I use to charge this battery from the car alternator while driving and what wire and car-to-caravan plug would be safe considering the caravan battery would about 22ft (7mts) from the alternator?

Any and all advice will be greatly appreciated.

  • Please don't shout - edit your question & title to lower case then people may read it.
    – Solar Mike
    Sep 5, 2017 at 4:32
  • you need to know the current requirement of the fridge. ( You only need the average current, as the battery will handle the startup ). A standard "7-pin" trailer plug has an aux pin for just this purpose..though I don't know the current limit.
    – agentp
    Sep 5, 2017 at 17:06
  • @agentp is correct. Large trailers with braking systems use the aux voltage to charge a battery used for emergency braking. This is a trickle-charge however, and trailer wiring is really only designed for the amperage of incandescent bulbs and small accessories. 10amps seems like a good guess for the limit.
    – JPhi1618
    Sep 6, 2017 at 20:16

1 Answer 1


The easy way out & ensure there’s no problem is to use a ‘ANDERSON PLUG SYSTEM’ from the tow bar/rear of car and a seperate lead to your battery on/in/mounted on the A frame of the caravan/camper... from there, run (a hard wired 2core cable) seperate line to the fridge in question to your wants... easily done ✅ whilst you have the car mobile or travelling along all ya need to do is mount a relay from the main car battery via: the ignition to pull in when after the car starts 😬 it will keep ya 🍻🍻🍻🍻 cold, by doing it to enjoy whenever ya pull over as well.. from another who’s done it themselves 😉

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