Can an grid-tie inverter be told to use the battery backup even when the Grid is running?

Outback and some other grid inter-tie inverters have a option to use batteries when the grid goes out. Can I tell the inverter to use the battery back instead even if the grid is on? ( I assume there is a test mode, to make sure everything's working?) I want get a inverter that has this mode so that when... show more Outback and some other grid inter-tie inverters have a option to use batteries when the grid goes out. Can I tell the inverter to use the battery back instead even if the grid is on? ( I assume there is a test mode, to make sure everything's working?) I want get a inverter that has this mode so that when electricity is expensive from the grid (I have real time pricing), I can just use my batteries to power the house instead. I don't want to sell any power back to the grid. Just use my batteries when its expensive to buy from the grid.
Thanks for the info!
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