Dual Pro B.O.S. Battery Optimization System - 12V - 3-Bank One Size. O. S. actively shuttles energy between batteries to keep the pack balanced increasing battery strength and longevity. Batteries in a pack will become out of balance and the pack is only as good as its weakest link. In watercraft applications this is further compounded when the trolling motor battery is used for peripherals and/or to assist the cranking battery. B. O. S. actively shuttles energy as needed between batteries wired in series to ensure equal voltage before during and after charging. B. O. S. keeps packs balanced enabling maximum performance and quadruples run time on the water. Premature battery failure due to an unbalanced pack has been unfortunately accepted as the norm for decades. The B. O. S. answers this call with a BSAP-24 algorithm that can accurately predict and select the battery that needs additional energy to match the other batteries within the pack. This simultaneously and successfully extends the life of each battery in the pack as well as increasing run times. Package Contents: Dual Pro B.O.S. Battery Optimization System - 12V Dual Pro BOS12V3: B.O.S. Battery Optimization System - 12V - 3-Bank One Size