I am charging a LiFePO house battery from my AGM starter battery using a Smart 12-12/18 Amp isolated charger (I am connecting the grounds to a common ground to convert it to non-isolated), but I want to manually control whether or not the Smart Charger turns on. I have an onboard charger that I plug in at the dock. But when using the dock power charger, I don't want the DC-DC Smart Charger powered on since my onboard charger has leads for each battery (or explain to me why it would be ok to allow it to sense the voltage at the AGM and turn on).
I have an accessory rocker switch available to use. My question is do I just connect the wires from L and H terminal to the rocker switch and will that open and close the connection in order to power the Smart Charger on? Or does it require a voltage at the rocker switch?