I have generator that automatically kicks on when my power goes out. It shuts down the grid connection before it does so to avoid feeding power back to the grid. You just need something similar that would cut off the grid when the power goes out and switch to your battery.
You can do this physically.
I requested octopus energy install an isolator switch before my distribution box, as my house is old enough to send the power directly into the home, before those external boxes with the earth, isolator and meter were implemented.
I have generator that automatically kicks on when my power goes out. It shuts down the grid connection before it does so to avoid feeding power back to the grid. You just need something similar that would cut off the grid when the power goes out and switch to your battery.
You can do this physically. I requested octopus energy install an isolator switch before my distribution box, as my house is old enough to send the power directly into the home, before those external boxes with the earth, isolator and meter were implemented.