A method for battery charging includes performing a first-constant-current charging the battery with a constant current having a first intensity, determining a voltage of the battery rises above a first voltage level, performing a second-constant-current charging of the battery with a constant current having a second intensity that is less than the first intensity, determining a voltage of the battery rises above a second voltage level that is higher than the first voltage level, performing a third-constant-current charging the battery with a constant current having a third intensity that is less than the second intensity, determining a voltage of the battery rises above a third voltage level that is higher than the second voltage level, performing a constant voltage charging the battery with a constant voltage having the third voltage level, determining a charging current of the battery falls to a fourth intensity that is less than the third intensity.