A method for charging a rechargeable battery, and a protection circuit for the rechargeable battery. The protection circuit perceives whether the battery is charged or not by sensing the voltage of the bare cell, changes the direct voltage applied between a gate electrode and a source electrode of a charging field effect transistor, which is connected in series between one terminal of the bare cell and one terminal of a charger, and controls the amount of the current flowing from the source electrode of the charging field effect transistor to a drain electrode at a low level, thereby maintaining a low charging rate of the battery.