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Equalizer system and method for series connected energy storing devices

United States Patent

5,952,815
September 14, 1999
View the Complete Patent at the US Patent & Trademark Office
An apparatus and method for regulating the charge voltage of a number of electrochemical cells connected in series is disclosed. Equalization circuitry is provided to control the amount of charge current supplied to individual electrochemical cells included within the series string of electrochemical cells without interrupting the flow of charge current through the series string. The equalization circuitry balances the potential of each of the electrochemical cells to within a pre-determined voltage setpoint tolerance during charging, and, if necessary, prior to initiating charging. Equalization of cell potentials may be effected toward the end of a charge cycle or throughout the charge cycle. Overcharge protection is also provided for each of the electrochemical cells coupled to the series connection. During a discharge mode of operation in accordance with one embodiment, the equalization circuitry is substantially non-conductive with respect to the flow of discharge current from the series string of electrochemical cells. In accordance with another embodiment, equalization of the series string of cells is effected during a discharge cycle.
Rouillard; Jean (Saint-Luc, CA), Comte; Christophe (Montreal, CA), Hagen; Ronald A. (Stillwater, MN), Knudson; Orlin B. (Vadnais Heights, MN), Morin; Andre (Longueuil, CA), Ross; Guy (Beloeil, CA)
Minnesota Mining & Manufacturing Co. (St. Paul, MN), Hydro-Quebec Corporation (Montreal, CA)
08/ 900,607
July 25, 1997
GOVERNMENT LICENSE RIGHTS The Government of the United States of America has rights in this invention pursuant to Cooperative Agreement No. DE-FC02-91CE50336 awarded by the U.S. Department of Energy.