A voltage sensitive relay (VSR) is the best way to ensure you can always get your dual-battery vehicle started. If the radio stops working that's one thing, but if you're stranded because your car cannot start because you ran your fridge for too long, that's potentially a life and death scenario. It allows two batteries to be charged from your alternator. Once your main starter battery is sufficiently charged, it will begin charging the second battery too. Fully automatic with emergency override.
Protects your starter battery
Ideal for 4WD, marine, and more
Current Rating: 125a
Voltage Rating: 12v DC (15v DC Max)
Cut-In Voltage: 13.7v DC
Cut-Out Voltage: 12.8v DC