The KickAss 12V Smart Battery Guard combines a voltage sensitive relay and a low voltage disconnect in one unit, so a single device both connects your auxiliary battery for charging and protects it from being flattened.

VSR and Low Voltage Disconnect in One

The two jobs are usually done by two separate devices. A VSR senses when the alternator is charging and links the auxiliary battery in, then disconnects it when the engine stops so your starter battery is never at risk. A low voltage disconnect does the opposite end of the job, it cuts the load off the auxiliary battery before it is drawn down far enough to damage it. Combining them means one install, one set of connections and one point of failure instead of two.

KickAss 12V Smart Battery Guard Specifications

• Voltage sensitive relay (VSR) function
• Low voltage disconnect (LVD) function
• 12V operation
• Protects both starter and auxiliary batteries
• Weight: 610g
• SKU: KASMARTBG

A VSR is not a DCDC charger. On a vehicle with a smart or variable-voltage alternator, a VSR will not fully charge an auxiliary battery, and it will not properly charge lithium at all. If that describes your vehicle or your battery, you want a DCDC charger instead.