The test field. Top row: Cole Hersee M750, Guest 2300A, Charles 93BS002, Middle row: Perko 8501, Guest 2111A, Perko 8603, Guest 2101. Bottom row: West Marine 382215, Blue Sea 9001e, BEP Marine 721, BEP Marine 701S.

Your vessel’s battery selector switch is probably one of the first things that you reach for each time you step aboard your vessel. And after you’ve left the boat, it’s the switch that plagues your mind: Did I turn that @$*^ thing off?

A battery selector switch’s primary purpose is to help manage the flow of electrical power onboard your vessel. This is accomplished by providing a selectable circuit path between your vessel’s batteries and the primary branch circuit, such as the main DC distribution panel or engines. …