Mike, thanks for a very helpful description. I am considering getting an Enphase PV + Battery system (with System Controller 3). One of my concerns has been exactly the scenario you described. The other is what happens when grid power returns after a long time and you have completely dead batteries. Isn't the battery power needed to run the System Controller so it can get at least grid power to your house? Do you also have a System Shutdown Switch wired to the System Controller (to force a direct connection of grid to your backup loads) and would that even work if the batteries were completely dead?