I was thinking along those lines a few weeks back myself. First off, the
grid makes for a 100% efficent and free "battery" so why bother with
your own batteries? If you are looking to have power during an outage
you'd need batteries but easiest is to charge them off the grid. Then
you need another inverter as the grid-tie units can't run when the power
is out. If your outages are often long you might want a charge
controller to use with the solar panels to charge your batteries - but
you can't run both the grid-tie inverter and charge controller at the
same time. A potential problem here is that the bigger grid-tie
invereters expect several hundred volts so you have to series connect
all your panels. Charge controllers expect much less voltage so you'd
have to reconfigure your panels to switch from grid-tie to battery
charging.