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A battery protection circuit for protecting a battery is proposed. The circuit includes a detecting circuit for detecting a battery condition and producing a detected voltage in relation to the battery condition, a comparator comparing the detected voltage with a given voltage, and a switching circuit controlling a connection between the battery and electrical elements. In the battery protection circuit, when the comparator determines that the battery needs to be protected from the battery condition, the switching circuit turns off to disconnect the battery from the electrical elements.

In communication equipment which uses a battery as the power supply, when a controller increases the transmission power at a transmitter corresponding to a drop in the electric field intensity, the controller lowers, accompanying that operation, a reference voltage from a reference voltage source which is used for comparison with the battery voltage for the purpose of detecting a drop in the battery capacity. Therefore, even when the battery voltage is dropped due to an increase in the transmission output, the reference voltage is also lowered correspondingly, so that there will not occur an erroneous detection of drop in the battery capacity due to the drop in the battery voltage.

A battery cell having a positive terminal, a negative terminal and a power producing core section (e.g., electrolyte) for systems, such as computer systems, cellular phones, etc. The battery cell also includes an internal circuit to monitor the state of the battery cell. The state that is monitored may include the temperature, charge level of the battery core section, the discharge/charge rate. The circuit may control the battery cell (e.g., cause charging of the battery cell). This internal circuit may be an integrated circuit, such as a microprocessor.

A lockout circuit is provided in a battery pack (10) which blocks charging by incompatible chargers while allowing charging by a compatible charger (12). The battery comprises a battery cell or cells (22), and a switch circuit (24). The switch circuit blocks charge current until a switch disable signal is provided to a switch disable contact (18). The switch circuit provides a one way bypass so that the battery may provide power to a device. To eliminate voltage drop while powering a device, a current sense circuit is provided to detect discharge current, and disable the switch circuit.

A battery heating device includes a temperature sensor and at least one heating element in a liquid and acid-proof arrangement inside the battery. The heating element is a power transistor secured to a cooling plate which is powered by the battery, the emitter of the power transistor being powered by a temperature control circuit when the battery temperature falls below a predetermined reference temperature and the battery voltage is higher than a lower threshold and lower than a higher threshold. A trigger circuit responds to a rise in battery voltage after the current in a load having a high current consumption is switched off. The trigger circuit actuates a timer circuit which conductively controls the power transistor for a set time if the battery voltage is under or at the lower threshold.