Quote Originally Posted by ditchsnake View Post
I'm trying to follow this as I want to add a 3rd battery to my setup. ! starting and two stereo. I'd only need a two bank charger as one would charge the starting battery and the other would charge the two stereo batteries wired together. I use the factory isolator. So chat happens when my charge goes above 13.8 volts? The charger would see both banks as one large battery? Confused
I'm assuming that you are using a voltage sensing relay (VSR, ACR), like a Blue Sea for example, rather than a diode-based isolator.
13.8 volts sounds high for any combining threshold.
In any case, the charge voltage can keep a VSR closed thereby circumventing the dual bank charger isolation.
If this applies to your situation you have three possibly remedies.
One, add A Blue Sea 5511e dual circuit switch that you turn 'Off' whenever the boat is put on the trailer and 'On' whenever the boat is splashed. This method requires that you reverse the Blue Sea schematic so the relay is on the opposite side of the switch from the batteries in order to fix charging isolation with the switch set to 'Off'.
Two, rather than add the 5511e switch, add a small manual switch to the low current ground wire of the VSR to disable it whenever the boat is in storage.
Three, use an AC relay that is tripped when the AC shore charger is plugged in to automatically disable the VSR.