LEISURE ELECTRICS INSTALLED BY BIG V
Campervan leisure electrics commonly include a 12 volt system which runs the LED lights, compressor fridge, pump for the water tap, 12 volt and USB sockets, and other 12 volt systems. These all connect to a leisure battery, which is almost identical to a standard vehicle battery except that it is designed for the slow drawing of power rather than the sudden, heavy draw that is needed to start an engine.
Additionally, it is common to have a 240 volt mains hook-up for connecting to power supplies at camp sites, with one or more standard mains sockets. This system is totally separate from the 12 volt leisure system unless additional parts are installed.
The diagram below gives a visual overview of the 12 volt and 240 volt systems, as well as some optional extras that connect to one or both.