What is the best way to charge my (1) AGM starter battery and (1) lithium house battery from my alternator when the motor is running? I watched your videos and it looks like an isolator would work? Not sure? - Carl
Battery isolators do not modify voltage but just share a charging voltage. Your lithium battery and AGM battery will want a different charge curve. Instead of a battery isolator, consider a DC to DC charging converter between AGM and Lithium.