Patent ID: 8026696

Claim:
A rechargeable battery pack, comprising: a power cell; a higher and a lower power supply rail; a first electronic switching device for charge control, operatively coupled to the power cell, wherein current passing through the power cell also passes through the first electronic switching device when the first electronic switching device is in a conducting condition; a second electronic switching device for discharge control, operatively coupled to the power cell, wherein current passing through the power cell also passes through the second electronic switching device when the second electronic switching device is in a conducting condition; a first protection circuit operatively coupled to the first and second electronic switching devices and configured to cause the first and second electronic switching devices to assume a non-conducting condition when one or both of an overvoltage and overcurrent condition exists; and a second protection circuit operatively coupled to the first and second electronic switching devices and configured to receive a negligible current from said power cell and to cause the first and second electronic switching devices to assume a non-conducting condition when a temperature in the rechargeable battery pack exceeds a threshold value, the second protection circuit having: a resistor coupled to the higher power supply rail; a thermal protector element, coupled between the resistor and the lower power supply rail, wherein the current passing through the resistor also passes through the thermal protector element; and a third electronic switching device operationally connected to a controlling terminal of the first electronic switching device, to a controlling terminal of the second electronic switching device, and to the lower power supply rail, said third electronic switching device also being operationally connected to the thermal protector element and to the resistor, said third electronic switching device being configured to assume a conducting condition, to cause the non-conducting condition of the first and second electronic switching devices when said thermal protector element has a high impedance as a result of a temperature within said rechargeable battery pack exceeding said threshold value.