The battery feeds the inverter, that is the only thing that is sufficiently low impedance to do that. The mill can't feed the inverter direct but whatever it is producing will be deducted from the batteries contribution to the inverter.
Say that the inverter is taking 60A and the turbine at any instant is giving 30A this means that at that instant the battery is only supplying 30A.
You can't get away with tiny batteries they must be capable of supplying the full inverter load for a significant time. On a very windy day you may get away with this approach but on most days it just won't work.
You only need a charge controller if the batteries are fully charged, if you watch the load manually a charge controller is just a luxury.
If you use small batteries then the chances are that they will be charged most of the time and the charge controller becomes more essential as you will not have the time to deal with the load situation manually unless you have a full time job acting as a charge controller.
The minimum battery size is dictated by the load you want from the inverter when the turbine is producing nothing or very little. If you can hold off not using the inverter on these days then a smaller battery would be adequate but a minimum size is needed to handle the peak inverter current without damaging the battery or tripping the inverteron low battery volts.
