Blue Sea 7650 Add-A-Battery Management Kit

The Blue Sea Systems 7650 Add-A-Battery Management Kit is a Dual Circuit Plus switch and a 120A SI Automatic Charging Relay for two-bank boats.

The relay is what does the work here. It detects charging voltage, combines the banks so both receive charge, then separates them again when charging ends. Without that, a two-bank boat charges one bank and leaves the other to whatever manual switching someone remembers, which is how a house bank ends up chronically undercharged.

Separating the banks again as charging stops is equally important, since leaving them combined means house loads draw the starting battery down overnight. The relay makes both transitions automatically rather than depending on the operator noticing the engine has stopped.

The Dual Circuit Plus switch controls the engine and house circuits while keeping the banks isolated in normal operation, with temporary combining available for emergency starting. This suits a boat adding a dedicated house battery or replacing a manual two-bank arrangement, where the switching and charging need to work together rather than being chosen separately. Explore more bus bars and power distribution.

• Relay combines the banks whenever charging voltage appears
• Separates them again so house loads spare the starter
• Manual switching leaves a house bank undercharged
• For adding a house battery or replacing a manual setup