Abstract: A battery charging system with redundant overcharge protection. The voltage across a plurality of series connected battery cells as well as the voltage across each individual cell is monitored both at a battery module and a host charging system. In the event an overcharging situation is detected, by the battery module, a first switch is open-circuited to prevent overcharging. In the event an overcharging situation is detected in the host system via a communication channel with the battery module or damage to the first switch is detected, a second switch is open-circuited in the host system to prevent overcharging, thus providing a redundant level of security against overcharging the battery cells.

Abstract: A battery pack including a secondary battery is coupled to an electronic device to behave as a power source of the electronic device. The battery pack comprises a plus terminal (EB+) and a minus terminal (EB-) for supplying a current to the electronic device, a communication terminal (DATAB) for exchanging data with the electronic device, a connection terminal (BATTINB) connected to said electronic device when the plus terminal and the minus terminal are properly connected to the electronic device, battery status measuring elements (6, 7) for measuring the temperature and the voltage of the secondary battery, and CPU (1) for establishing one of operation modes in response to the voltages at the communication terminal and the connection terminal.

Abstract: A battery pack has a current detector, a voltage detector, a temperature sensor, and a CPU. The current detector detects a current flowing in secondary cells. When the current flows in the secondary cells, the voltage detector detects the voltage of the secondary cells, and the temperature sensor detects the temperature of the secondary cells. The CPU calculates the extent of deterioration of the secondary cells. The CPU calculates the remaining capacity of the secondary cells, based on the open voltage of the secondary cells, OCV, obtained by the equation:OCV=DV+K.times.DI.times.T.times.Fwhere DV represents the voltage of said secondary cells when used; DI, a current flowing in said secondary cells; T, the temperature of said secondary cells; F, the extent of deterioration of said secondary cells; and K, a predetermined proportional constant.