7649 Mini Add-A-Battery What does the Mini Add-A-Battery do? Adding a second battery prevents getting stranded with a dead battery by isolating the start battery from the house loads that can quickly discharge a battery. The Mini Add-A-Battery offers a compact simple way to control the switching with the m-Series Dual Circuit PlusT Battery Switch and automatically share a single source of charging between two batteries with the Mini ACR Automatic Charging Relay. Product : BLUE SEA 7649 MINI ADD A BATTERY Manufacturer : BLUE SEA SYSTEM Manufacturer Part No : 7649 UPC : 632085076498- SKU: CW47527.