Blue Sea 7649 Mini Add-A-Battery Kit - Boxed Packaging [7649003]7649 Mini Add A Battery Kit Boxed Packaging 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