VOLTAGE SENSING BATTERY ISOLATOR RELAY INSTALL

charge both batteries at the same time or the ability to link both batteries for either vehicle starting or to power accessories under extreme load… heavy and prolonged winching for example. However, these relays are slightly more sophisticated and have the ability to dual feed – i.e. If the voltage on the vehicle starter battery drops, the relay switches back. Once the engine is running and the relay determines the starter battery is fully charged, it switches the output of the alternator to the vehicle accessory battery. In normal operation the relay connects the output of the alternator to the starter battery. If you look at the drawing above, you can see the alternator output goes straight to the split charge relay.

VOLTAGE SENSING BATTERY ISOLATOR RELAY INSTALL

Never use the vehicle body as a conductor, always install correctly sized earth (neutral) cables. Note: I haven’t shown any fuses or earth (neutral) cables. SCR’s are normally solid state, I have shown it as switches to make it clearer. Modern SCR’s are usually all solid state and some times have a bypass switch allowing both batteries to be directly connected for either starting the vehicle if the starter battery is flat or to allow the winch to be powered from the starter battery in emergencies. As the winch uses a lot of power, it is necessary to be able to recharge this battery as fast as possible using the output from the vehicle’s alternator, so once the vehicle starter battery is fully charged, the output from the alternator is switched directly over to the second battery. The general idea is the winch is powered from a second battery so that using the winch should never flatten the main vehicle starter battery. These are usually installed in 4 x 4’s that have a lot of accessories fitted especially electrical winches. Finally a VSR – Voltage Sensing Relay is similar to an SCR but turns on and additional circuit at a pre set voltage. So what do you use each one for? Split Charge Relay – SCR An SCR or Split Charge Relay is a switch that senses voltage and switches over from one circuit to another at a pre set voltage. So what are they? A relay is just a simple switch that allows a low power electrical circuit to turn on (or off) a high-powered electrical circuit. There is a lot of confusion over what the differences are and when to use each one.

Voltage sensing battery isolator relay