That depends what you are running from it, so a few equations are needed! 1. Firstly, all batteries are measured in Amps, so you need to know that 2. Now divide this by the number of Amps the device uses. Remember if you are running more than one appliance you'll have to add all the Amps u. If the caravan does not have either a consumer unit or a Zig unit, one must either be installed or see the instructions for getting electricity into a. There are 3 type of battery charger: 1. Trickle Chargers (Float Chargers) - A 12 volt battery will perform better if it is kept fully charged when not in use. A trickle charger is designed to be left on to top the battery up and will then. There are two types of battery: 1. Shallow-Cycle batteries (vehicle batteries) a. Which are designed to give large amounts of current, but only for short.