Abstract

A battery charging system is arranged to reduce a bypass capacity and to enable a charging operation with high current. A plurality of single battery cells 1 connected in series is connected to a charger 6, and each cell is connected in parallel with a constant voltage circuit 4 having a constant voltage control section 2 and a current saturation detecting section 3. The constant voltage control section 2 detects the terminal voltage, compares the detected terminal voltage with a preset voltage, and control the terminal voltage so as to be held constant by causing the charging current to bypass in accordance with the error resulting from the comparison. The current saturation detecting section 3 sends a command signal through an OR circuit to the charger 6 when the bypass current becomes saturated, and the charger 6 reduces the charging current in response to the command signal. Therefore, the capacity of the bypass current can be set at a lower level, and the high current charging is possible.