Yes I have 2 eg4 power pro wall mount batteries. They're 48v 280Ah each.
Here's what they say about AC Coupled mode straight out of the manual-
"After the AC couple function is enabled: When the grid is on, the GEN terminal is connected to the GRID terminal inside the inverter. In this case, the hybrid inverter will bypass the interactive inverter AC to the GRID and LOAD. Any remaining energy will be exported to the grid. When the grid is off, the GEN terminal is connected to the LOAD terminal inside the inverter. In this case, the hybrid inverter will work as a power source for the grid-interactive inverter to synchronize and feed power to the micro-grid. The loads will be supplied by solar power first. If solar panels are generating more power than load consumption, the excess solar power will be stored in the batteries. When solar power exceeds the sum of load power and max battery charging power (e.g., when the batteries are nearly full), the inverter will signal the grid interactive inverter to reduce power via the frequency shifting, power-reduction mechanism, thus maintaining the balance of generation and consumption of the micro-grid system."
I'm confirming with EG4 about this as well.
I guess my only confusion at this point is what I do with that 100amp back feed breaker. Do I leave it in there or downsize it to say a 60 or 70amp?
In my setup, my shop will be ran completely off the inverter and batteries. It's not going to pull anything from the grid. The only function the "grid" lugs will have is selling excess power back to the gride when the batteries are full, so I won't be pulling 60,70, or 100amps (whatever size backfeed breaker) So in theory I wouldn't be sending anymore power back to the grid than I currently am now through that 100amp breaker.