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 switching
Isolates engine and house circuits
Combines batteries for emergency starting
Tin-plated copper studs for maximum conductivity and corrosion resistance
 
 
ACR Automatic Charging Relay 
Automatically combines batteries during charging
Isolates batteries during engine cranking and when not charging
Shares the charge between two batteries more efficiently than a battery isolator
Allows efficient dual battery charging without needing regulator adjustment or rewiring