Battery low voltage cut-off circuit driven by microcontroller
A soft power latching circuit like this one should do the trick. Power can be switched off by pulling the SHUTDOWN input low. C1 will prevent the circuit from switching on again immediately after it was switched off.







simulate this circuit &ndash; Schematic created using CircuitLab

Make sure to use a logic-level MOSFET that only needs 3 volts of gate voltage.