Blue Sea Systems Add-A-Battery Solenoid The ADD-A-BATTERY is as simple to operate as an ON-OFF switch, yet effectively manages the switching and charging of two batteries from a single charge source The Add-A-Battery includes a Dual Circuit Plus Battery Switch and an Automatic Charging Relay. These components simplify switching and automate charging, so that all you have to do is turn the battery switch ON when you arrive and OFF when you leave. Dual Circuit Plus Battery Switch Simplifies switch