Sierra BS11040 Voltage Sensitive Relay 12V 125A Battery Combiner

The Sierra BS11040 Voltage Sensitive Relay is an intelligent battery management solution designed to automatically combine and isolate dual battery systems in marine, RV, and powersports applications. This relay eliminates the voltage drop associated with traditional diode-based battery isolators while protecting your starting battery from being drained by accessory loads.

Key Features:

• Automatic battery combining at 13.3VDC when charging, isolation at 12.8VDC when not charging
• 125A continuous current rating with 140A intermittent capacity
• Zero voltage drop operation—maintains full charging voltage to both batteries unlike diode isolators (0.6V drop)
• 12VDC nominal voltage operation
• Low power consumption: 10mA standby, 330mA when engaged, 0mA in storage mode
• Durable glass fiber reinforced nylon enclosure for harsh marine and outdoor environments

This voltage sensitive relay automatically monitors battery voltage and connects batteries when the alternator or charger is running, allowing both batteries to charge simultaneously. When charging stops, it isolates the batteries to ensure your starting battery remains fully charged. Ideal for boats, RVs, and vehicles with dual battery systems requiring reliable auxiliary power without compromising starting capability.