In this section we show some system examples which apply to vehicles with varying requirements from a simple battery powered system up to a full sized truck with permanent mains supply and power failure back-up. The schematics show how the electrical power from the engine driven DC alternator of the vehicle can be stored in extra batteries and used by power inverters to create AC power from the DC power supplied by those batteries. In caravans and towed trailers, this can come from the tow vehicle engine when connected and then mains can be connected when stationary which through a charger charges the battery for the lights. Alternatively, for bigger installations, AC diesel generators can produce 230VAC directly or, together with advanced inverter/chargers, provide a seamless supply of power.

Caravan or Trailer

When the trailer is being towed, the tow vehicle alternator charges up the service battery. When stationary, it is normal to connect to a source of mains and use this internally as well as to keep the battery charged. The battery usually provides power to lights and water pumps. The Cristec Mains Power Charger Unit is a very easy and convenient way to provide a ring main installation on a trailer which also includes a 12V battery charger.

Camper Van

When the van engine is running, the vehicle alternator charges up the start battery. It can also charge up another battery via a splitter or voltage sensitive relay. The second battery can now be used to supply DC 'services' such as interior lights and water pumps without fear of flattening the start battery if the engine is not running. Furthermore, the second battery can also be connected to a power inverter to supply pure sine wave 230VAC. The 230VAC can be used to provide power for laptops, electrical tools or even a microwave to cook food. As equipment is used, it consumes the energy stored in the second battery but it does not deplete the start battery. If power is required for longer periods, then the van engine can simply be started and left idling.


The ultimate on-board power package comes from combining all the sources of energy into a system which provides a seamless source of continuous 230V mains. We have developed solutions that involve the use of world leading inverter/chargers with high speed automatic transfer switches and programmable load shedding relays – all built in. The power of the generator assisted with this type of system, combined with AGM batteries and complimented if needs be by the engine driven DC alternator, offers the ultimate system. It provides permanent 230V supply which, when the generator is running is very powerful but, if the generator stops, significant levels of power are still available to ensure systems remain up and running.