How to Add the Second Battery for Cravan or Caravan Truck with a VSR

In most Yachts and Caravans (Camper Vans), a second battery (also named dual battery setup) is often pre-installed in factory or modification shop. But if you’re going to convert your truck or RV into a camping vehicle, a “dual battery setup” is definitely on top of the check list.

The idea of dual battery setup is basically to have two batteries that are both being charged while engine is running but only one of them is being drained by the devices or DC appliance being used when engine if shut off. In this way you will still have a battery with enough power to start the engine (so it can charge the batteries again). The first battery is often named Start Battery which connects to the engine and should remain fully changed, and the second battery is the House battery that take cares of most of the loads on the daily use of your mobile “house”.
In practice, the two batteries would be connected in parallel as shown in the drawing below while the engine or alternator being connected to the start battery together with other essential devices like radio or GPS, and all the heavy loads and electronics devices connects to the house battery. The two batteries are connected when charging so that both batteries can be charged and are disconnected (separated or isolated) when engine is off and power being drained at the house battery. Therefore you would need a way to be able to connect the batteries when needed and disconnect them when not needed.