Charging your
battery while towing

IAN HEWLETT finds out whether all cars will charge a leisure battery and run the fridge while towing

Charging your battery while towing

By IAN HEWLETT

Posted on 31 March 2017

Most UK specification caravans and folding campers (and some mainland European models) can charge their leisure battery and keep the fridge cool from the tow car when they are on the road. While the tow vehicle’s engine is running, electrical power is supplied via the traditional grey or white-capped 12S socket or (more commonly now) via a fully wired 13-pin connector. In theory, this should be able to keep the fridge cool, as long as it’s already pre-cooled, and put a small top-up charge into the leisure battery. In order to do this, you need to have the wiring, connections and enough capacity to achieve it. Older vehicles have control measures built into the alternator that sense the voltage from the car and control charging around a predetermined range (nominally 13.8 to 14.4V). As long as you have a supplementary wiring kit and voltage-sensing relay, everything is in place to power the caravan while on the move.