Siren Marine Battery Sensor f/Siren 3 [SM-WLS3-BATT-917]Battery Sensor for Siren 3 Monitor battery voltage with the Wireless Battery Sensor, and never worry about a dead battery again. Attach the Battery Connector to one of the boats batteries and plug the other end into the Wireless Module. Link the module to the Siren 3 Pro and receive alerts if the battery voltage exceeds or drops below a preset level. Ideal for monitoring multiple batteries on a boat. Features: Compatible with Siren 3 Pro only