Overcharge protection circuitry for rechargeable battery pack

Patent 5867008 Issued on February 2, 1999. Estimated Expiration Date:

June 3, 2017. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.

Abstract Claims Description Full Text

Patent References

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Inventors

Assignee

Double-Time Battery Corporation

Application

No. 868002 filed on 06/03/1997

US Classes:

320/136With battery or cell condition monitoring (e.g., for protection from overcharging, heating, etc.)

Examiners

Primary: Tso, Edward H.

Attorney, Agent or Firm

International Class

H01M 010/46

Abstract

A self-contained, rechargeable battery pack uses a coulomb-counting control circuit to measure charge received by and taken from the cells and to store a current charge status of those cells. The control circuit controls a charge/discharge pass transistor in the pack to provide overcharge protection. An always-on trickle charge resistor insures that the controller is in operation during charging even when the cells associated with the controller are completely discharged. A Schottky diode is placed across the charge/discharge pass transistor in order to minimize the discharge dropoff voltage between the terminal of the cell and a corresponding external terminal. The present invention considerably lengthens the useful life of nickel-based rechargeable batteries, as measured in terms of both the number of cycles and the available capacity per cycle, while requiring no extra terminals.

Other References

bq2004 Fast-Charge IC, Benchmarq Microelectronics, Inc., Jan. 1998, pp. 1-16
bq2012 Gas Gauge IC, Benchmarq Microelectronics, Inc., Jul. 1994, pp. 2-263-2-282
bq2014 Gas Gauge IC With External Charge Control, Benchmarq Microelectronics, Inc., Dec. 1995, pp. 1-2