Charging Battery

In the use case that @rmcarthur described, there isn't any power coming in from the WFCO converter. The charger will supply the 12v load drawn by the WFCO and any excess ends up in the battery. This is a typical use case with solar, AC mains or generator input to an AC charger. I was once 'boondocking' in an off-grid campsite close enough to our neighbor to run an extension cable over to the 20A outlet on their 50/30/20A power hookup to connect my Victron IP22 to their 20A outlet (they were only using the 30A outlet), and the IP22 happily supplied sufficient power for our 12V draw and kept the batteries hovering around 100% capacity.

Additionally, when arriving home after boondocking with low-ish battery levels, hooking up both the 30A input to the WFCO plus 20A to my IP22 for my batteries resulted in nothing other than my batteries charging more quickly than usual. In fact, this is my usual approach to battery charging before leaving home, since my 'auto' select WFCO power center seems to always somehow knock itself out of Lithium mode and fails to adequately charge my 2x 100Ah LiFePo4 batteries.