Motorhomes normally contain a 12V DC electrical system which is supplied from a separate leisure battery. At a bare minimum this supply is used to operate lights in the habitation section but it can also be used for pumps, operating the heating and other accessories such electric steps. 240V AC outlets may be provided for use when the camper is connected to the mains supply at a campsite.
The 12V system operates from a separate battery - the leisure battery. This should be a deep cycle battery which can better withstand deep discharge cycles. A starting battery is optimised to provide brief bursts of very high current for starting an engine and will not provide long life if used as a leisure battery.
The leisure battery can be charged by the engine-driven alternator through a split-charge relay. The connection is only made when the engine is running which prevents discharge of the vehicle's starting battery when the engine is stopped. The 12V heater in an absorption fridge is usually connected through the split-charge relay too.
A mains charger is also provided to charge the leisure battery when the motorhome is connected to the mains supply. On some vehicles the starting battery is also charged when connected to the mains.
A distribution board with fuses or circuit breakers controls the distribution of power to the various circuits and may contain meters to monitor the battery voltage. A single main switch should be provided to isolate all circuits from the leisure battery. Turn this switch off whenever the motorhome is unoccupied.
Care should be taken to avoid either battery becoming fully discharged as this can greatly reduce the battery life. If storing the vehicle for long periods it may be advisable to disconnect the batteries as small parasitic loads will flatten them. Note that on modern vehicles, on board electronics may not react well to the battery being disconnected. A better strategy may be to take the vehicle for an occasional drive during the winter or, if this is not possible, to turn the charger on from time to time. It is not advisable to leave the charger plugged in continuously for long periods.
Normally a mains Euro connector is provided on the outside of the camper to enable connection to the mains supply via an appropriate cable. A consumer unit containing circuit breakers may be used to isolate the vehicle from the mains supply. The battery charger is connected to the 240V AC supply and is used to keep the 12V DC system operating when connected to the mains. A three-way fridge should also be run on mains power when available. Electric power outputs may be provided throughout the motorhome. These are supplied from the mains connection. If the motorhome has been imported from the continent these outlets will normally be of the European type and an adapter will be required to connect ordinary plugs. Some motorhomes may contain one or more interior lights which operate from the mains supply.
Be careful when using electric heaters or microwave ovens because of the high power required. Note that some continental camping sites limit the maximum current to as little as 6 Amps. This is equivalent to approximately 1.5kW which may not be sufficient for a high powered appliance, especially when the power consumption of other devices such as the battery charger is considered. Attempting to draw more than the allowed current will trip a circuit breaker which may require the warden to reset.
The hot water boiler, which normally runs on gas, may also contain an electric element which is powered by the mains supply.
The electrical systems should require no attention if maintenance free batteries are fitted. Otherwise it may be necessary to monitor and top up the electrolyte levels in the batteries.