Patent ID: 8358136

Claim:
In a rechargeable energy storage system ( 230 ) characterized by a series arrangement (S 1 , S 2 , . . . S n ) of multiple battery cells (C 1 , C 2 , . . . C n ), multiple individual energy dissipative devices (D 1 , D 2 , . . . D n ) each associated with and selectively connectable and disconnectable (SW 1 , SW 2 , . . . SW n ) in parallel with a respective one of the multiple battery cells (C 1 , C 2 , . . . C n ), circuitry ( 240 , V c1 , V c2 , . . . V cn ) for measuring the voltage (V cell — 1 ) across each of the respective ones of the multiple battery cells (C 1 , C 2 , . . . C n ), and circuitry ( 240 , 36 ) for measuring the magnitude and direction of current (I bat ) flowing through the series arrangement of multiple battery cells and any dissipative devices connected in parallel therewith, a method of providing a measure of current flow (I batnet ) through substantially only the multiple battery cells comprising the steps of a) establishing a respective predetermined impedance (R) for each of the energy dissipative devices (D 1 , D 2 , . . . D n ); b) determining ( 240 , 246 , SW 1 , SW 2 , . . . SW n ) which of the multiple individual energy dissipative devices (D 1 , D 2 , . . . D n ) are actually connected in parallel with respective ones of said battery cells (C 1 , C 2 , . . . C n ); c) determining ( 240 , 310 , 244 , V c1 , V c2 , . . . V cn ) the voltage across each of said battery cells to which said energy dissipative devices are actually connected in parallel; d) determining ( 240 , 420 ) the current (I dis ) in said respective connected dissipative devices; e) summing ( 240 , 430 ) the said currents (I dis ) in the respective said connected dissipative devices to provide a measure (I distot ) of the total dissipated current; and f) subtracting ( 240 , 460 ) the summed dissipated currents (I distot ) of the said connected dissipative devices from the current (I bat ) measured through the combined series arrangement of multiple battery cells and any energy dissipative devices connected in parallel therewith to provide a compensated measure of current (I batnet ) in substantially only the series arrangement of multiple battery cells.