Battery to Battery charger as best solution- reality check

[john61ct]

Which brings us back on topic, as to when a B2B charger is required rather than the "voltage following" VSR/ACR/combiner.

Or your Balmar Digital Duo:

Regulates from the source House bank circuit to the target Starter battery, not useful between the alternator and its target battery.

Yes can adjust the isolate/combine setpoints, but

does not independently drop to Float, follows the upstream source.

Can step down voltage (buck conversion), but not boost to a higher one.

Not suitable when target battery is AGM and gets well depleted, e.g. bow thrusters, windlass or other high demands.

Can go up to 30A, but

does not itself limit current, just cuts out for OCP (latching style) and needs to be manually reset in order to go back to combining mode.