Not a good idea. If you want PV power when the grid is off you really need AC or DC coupling. Search the forums for "coupling" and you'll find folks asking the same things.
Normal inverters are voltage-sources, they only supply current when the voltage dips. Grid-Tied inverters are current-sources, they keep raising the voltage until they can push current; so they need a controller somewhere to turn them on/off or throttle their capability to be safe. There's a lot of engineering with the batteries and their SoC that needs to happen.
Enphase has the Ensemble system. I believe a number of companies (e.g., Outback, Tesla powerwall, Victron) all have AC coupling solutions compatible with Enphase.