Two battery’s being charged?

[phatdaddy]

An important factor is how many amps your OB is putting out. I think mine has a 60 amp alt, so i feel like it is more that capable of keeping two batteries up.

[spareparts]

back to the OP question, its an ACR( Automatic charging relay) It allows both batteries to be charged independently regardless of battery switch position without linking them for discharge. Y9u can do the same with a battery isolator but it takes a bit more wiring. The ACR is fairly simple to wire in place. Fun fact, if you have a Yamaha, its got a secondary charging coil that's not being used that allows you to charge two different systems independently. Yamaha sells a kit, but its nothing more than some red wire and couple connectors.