2021 Sprinter. When not used regularly there is a parasitic drain that on battery. Am told this is normal for Sprinters. House batteries are lithium, want to use them or existing solar to keep starter charged up. This is an issue because lead and Lithium are not compatible. AMP-L used to make a device that allowed house to charge starter but they are out of business. Options?
I have the same issue. would be interested in a solution.
Put a SPDT switch on the output of your solar controller one output to the house battery the other output to the start battery so you can A-B them, just make sure the switch can handle the current (amps) from the panels. A marine battery A/B switch would work it would be major overkill on amp capacity. Check out the small A/B switches on BlueSeas Systems.