Over or Low Voltage  Detection using  Op-Amp

It is a very common op-amp Schmitt Trigger like circuit with some modification. Basically, it detects the Higher and Lower limit of this Vcc as the Vcc fed to the input.

The upper and lower threshold voltage Range can be adjusted by POT4 and POT2 respectively. TL431 used for better stability but one can use zener instade.

In this circuit, the value of components chosen for a 6v battery over charge and over discharge protection circuit.In place of transistor and LED MOSFET could be used which will be trun off or on load and charging.

It is bit complexes while same functionality could be achieved by less components. But this will be a stabilizes option for "over voltage detection" or "lower voltage detection" and very useful for battery management circuits.