Over charging protection circuit

I am making an over charging protection circuit for a 12V, 30Amps battery. I am confused that when charger will be removed, will the battery voltage remain at same potential as the potential with charger? E.g when charger is connected voltage measured is 14.2V, when the charger will be removed, battery voltage will be 14.2 or less than 14.2?

The battery no load voltage will drop to around 12.8V (room temperature). If the battery wasn't fully charged, the voltage will drop to a lower value.

The open circuit voltage of a lead acid battery depends on the state of charge (SOC) and temperature.

Using a charge voltage of 14.2V at room temperature for prolonged time, is too high. A good charger will reduce the voltage automatically to the "float" voltage (around 13.7V) after some time.