AC impedance testing for valve regulated cells

The author describes how the AC impedance of a valve regulated lead acid (VRLA) cell can be an indicator of the condition of the standby battery system. Used in conjunction with load cycle testing impedance testing identifies cells requiring replacement, reduces performance testing, and reinforces confidence in the battery system. Test results are presented which confirm the impedance test as the first true diagnostic test for VRLA cells. The condition of VRLA battery systems is examined, common failure modes are identified, test regimens are described, and actual test data are presented.>