Patent ID: 6922058
Filing Date: 2005-07-26
Classification: G01R

Abstract:
1. In a system having a plurality of rechargeable battery cells arranged in at least one string having a plurality of serially connected battery cells to form a battery system and including a charger coupled across said at least one string, a method for determining the internal impedance of each of said plurality of serially connected battery cells in said at least one string while the battery cells remain connected in the battery system, the method comprising the steps of: a) drawing a first predetermined current I b) measuring the voltage V c) measuring the voltage V d) drawing a second predetermined current I e) measuring the voltage V f) measuring the voltage V g) solving the two simultaneous equations for Z 1 and Z 2 , where Z 1 is the internal impedance of said first battery cell and Z 2 is the internal impedance of said second battery cell; h) calculating an impedance multiplier term IM from the equation and i) for each of the remaining battery cells in said at least one string