Switch-over from DC to AC

[deonhitchcock]

I suffer from sleep apnea and have to stay connected to AC power at night. I have a 300W panel, MECER 2000VA inverter with MMPT controller, and 2/12v 100ah batteries. When the inverter is connected to AC, there is no interchanging power tracking - only power tracking between solar and battery when disconnected from mains . Is there an automatic switch available to cross over from DC to AC when batteries are running low? Presently running on a 2hrs off/on cycle to compensate for inconsistency in weather and ESKOM.