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1. (WO1998052270) EQUALIZATION OF SERIES-CONNECTED CELLS AND BATTERIES

Pub. No.:    WO/1998/052270    International Application No.:    PCT/US1998/009825
Publication Date: Fri Nov 20 00:59:59 CET 1998 International Filing Date: Fri May 15 01:59:59 CEST 1998
IPC: H02J 7/00
Applicants: ADVANCED CHARGER TECHNOLOGY, INC.
Inventors: PODRAZHANSKY, Yury
PODRAZHANSKY, Mikhail, Y.
KUSHARSKIY, Yefim, Y.
Title: EQUALIZATION OF SERIES-CONNECTED CELLS AND BATTERIES
Abstract:
A charge pulse (200A) is applied to the battery (B). The open cirucit voltage of each cell (C1-CN) is then measured during a first rest period (210A). A depolarization pulse (220A) is then applied to the battery. The open circuit voltage of each cell is then applied to the battery. The open circuit voltage of each cell is then measured during a second rest period (210B). The open circuit voltages for the first and second rest periods for each cell are compared to yield a voltage difference (DELTAY). This voltage difference is then compared with a threshold voltage (VTHRESHOLD). If the voltage difference is greater than the threshold voltage then the cell is being charged too rapidly, or is being overcharged, so one or more of the charge cycle parameters are adjusted. Some of the charge cycle parameters are, for example, the charge pulse current amplitude, the charge pulse duration, the number of consecutive charge pulses, the depolarization pulse current amplitude, the depolarization pulse duration, the number of consecutive depolarization pulses, the duration of the rest periods, or a combination of these. Multiple charge pulses (200A, 200B) and depolarization pulses (220A, 220B, 220C) may also be used. These parameters may be adjusted for the battery as a whole and/or for each cell individually. The adjustment to the charge cycle parameters may also be made on a 'worst case' or a 'best case' cell basis, with this cell controlling the charge cycle parameters for all the cells. Several techniques for adjusting the charge cycle parameters are disclosed.