I have a lead-acid starter battery and a lead-acid service battery. There is a Cyrix switch between the starter battery and the service battery. An MPPT charger is connected between my solar panels and the service battery. What should I install between the lead-acid service battery and a lithium battery that I’m yet to buy?
A Victron Orion DC to DC battery charger, this way both batteries get proper charging. Which Orion you choose depends on the charging current you want to pass to the lithium battery.