Method and apparatus for testing cells and batteries embedded in series/parallel systems

Abstract

A 'three-point' measurement technique effectively removes system effects to determine impedance, admittance, resistance, or conductance of an individual cell, battery, or interconnecting conductor embedded in a series or series-parallel electrochemical battery or fuel cell system. Three electrical contact points are defined. Two of these points bound the subject element. The third point is separated from the other two by a conducting path that may include one or more cells or batteries. By measuring dynamic parameters between alternate pairs of contact points, three dynamic parameter measurements are acquired. A mathematical computation combines the measurements and determines the dynamic parameter of a subject element as if it were alone—thus effectively 'de-embedding' the subject element from the remainder of the system. A “four-point” extension of this technique permits measuring a dynamic parameter of a cell/battery disposed in a multiple-unit string of parallel-connected cells/batteries.