Today I temporarily connected the MultiPlus II to the Sub Board in my shed (Phase L1) with 6mm electrical cable and turned it on.
The inverter came to life and started supplementing my usage perfectly as it should. Below is a screen shot of what my Enphase graph looks like with the battery.. The consumption perfectly matches generation with virtually no import and only a tiny bit of export (during the middle of the day when the solar was producing more than the inverter could use to charge the battery.
The blue is the generation
The Orange is Consumption
The Black is either import (above the line) or export (below the line)
I wish it was this sunny every day.