Manufacture a solar inverter

im looking for a solar inverter around 6 Kw = inverter charges 6 x 24v battery's to give my home a stand alone electricity. once the battery are charged all the excess production of electricity by solar goes back to grid and after battery's run out or go bellow manageable level inverter put us back on grid electricity.(in the day time if the inverter can provide us standlone while charging battery that will be great)(night time will be fully battery operated system as solar doesnt work) we have a 6 kw solar system with direct grid connect its producing minimum of 14 kw per day as average and good days it can go above 20 kw/d. our average consumption of our house per day is 6.5 kw/d. ( inverter should be smart to detect overload, low solar production to switch us on full battery stand alone(as standard solar inverter keeps it self on even in very low sun light)