Is your power system connected to more than one battery? You need a high-quality voltage sensitive relay. Choose from our wide range of high-quality voltage sensitive relays from Enerdrive, Victron, Projecta and Baintech.


What Is A Voltage Sensitive Relay?

A Voltage Sensitive Relay (VSR) is popular in dual battery systems, usually in 4WD vehicles.  The VSR is essentially a switch triggered by the input voltage of an electrical current. It’s important to note that it will only work in standard alternator setups. It won’t work on smart alternators because they vary their voltage and won’t trigger the relay properly.


How Does A Voltage Sensitive Relay Work?

The voltage sensitive relay is connected from the main battery through a fuse to the auxiliary battery, which will run power appliances like a fridge while you’re camping. When the alternator is running and the voltage builds up, the voltage sensitive relay will cut in at 13.3V and connect the auxiliary battery so both batteries are charged from the alternator. When you turn off the vehicle and the voltage settles down, at 12.7V the relay will cut out, disconnect the auxiliary battery from the main battery so it is isolated. You can drain the auxiliary battery while camping but always be able to start the vehicle and drive away.