Victron MultiPlus C 12/1600/70-16 charges starter from the house bank

[pwfarnell]

You could always read the FAQ document which describes the trickle charger. You seem to have independently worked it out.

How does the Multiplus trickle charger work

The trickle charger on the Mutliplus is not a true charger, it does not have a set charge voltage. It is a small circuit that is connected directly to the DC input header within the Multiplus and it contains a current limiter and a diode. The diode is to prevent the starter battery from charging the domestic battery if the domestic battery has the lower voltage. See the diagram below. This means that the trickle charge function is always active, therefore if you have solar connected to your dome…