Field and laboratory studies to assess the state of health of valve-regulated lead acid and other battery technologies using conductance testing

This paper demonstrates the high correlation of capacity and conductance on hundreds of cells in telecommunication, UPS, railroad signalling and other usages. It confirms the premature capacity loss of valve regulated lead acid (VRLA) cells reported previously and provides information on failure modes via post mortem tear-down of some of the defective cells. Further, it extends the correlation of conductance and capacity to flooded lead acid cells and provides preliminary data of capacity conductance correlation with flooded nickel cadmium (Ni-Cd) batteries. It also introduces the results of techniques of noise suppression to allow online conductance measurements to be made on the batteries without interruption while the batteries continue in service