Patent ID: 8269458

Claim:
A rechargeable battery system, comprising: a battery pack operable to deliver a discharge current and to receive a charge current from a charger, the battery pack including: at least one battery cell; a first pair of terminals; a temperature sensor extending between the terminals; and a battery management unit that measures voltage of the at least one battery cell and is electrically connected to a given node of the temperature sensor to determine a temperature associated with the battery pack using the temperature sensor when the battery pack is disengaged from the charger; a charger operable to engage with the battery pack and supply a charge current to the battery pack, the charger including: a power supply circuit; a second pair of terminals that engage with the first pair of terminals when the charger engages the battery pack; and a charger control module electrically connected to the given node of the temperature sensor through one of the terminals and operable to directly determine the temperature associated with the battery pack from the temperature sensor when the battery pack engages the charger; wherein the battery management unit is configured to: periodically power up to determine whether the battery pack is engaged with the battery charger; power down when determined that the battery pack is engaged with the battery charger to create a high impedance at the given node of the temperature sensor; and communicate a signal to terminate charge current through the given node of the temperature sensor to the battery charger by pulling the given node of the temperature sensor to a low voltage when the measured voltage of the at least one battery cell in the battery pack exceeds a high voltage threshold.