PURPOSE: To eliminate the reset of a timer for setting the charging time of a charger if a battery is overcharged at a low temperature, to reset the timer when it is not overcharged and to suitably charge by providing the timer and battery temperature detecting means.

CONSTITUTION: When the temperature of a storage battery 3 is not high, a charging circuit 2 is timer-controlled by a controller 6 by a timer 9. When a temperature sensor 4 detects that the temperature of the battery 3 is raised due to its overdischarge or high output discharge, a temperature control discriminator 5 controls the temperature, a discharge circuit 10 is operated for a predetermined period of time thereby to discharge the battery 3 for a predetermined period of time. A discriminator 11 detects a voltage (VO) after discharging, and compares it with a reference voltage (VS). The discriminator 11 does not output in case of VO>VS, but it outputs in case of VO<VS thereby to reset the timer 9 through a resetter 8, thereby operating the charging circuit 2 through the controller 6 until the timer 9 is set up. Thus, it can prevent the battery from insufficiently charging, thereby always obtaining a sufficient battery capacity.