Performance Characteristics of Five Candidate Secondary Batteries for Photovoltaic Power Systems.

This document provides the Coast Guard with the results of baseline capacity, overcharge, and state-of-charge tests conducted on five candidate secondary batteries for photovoltaic power systems. Three candidate batteries DELCO-REMY, GLOBE UNION, and J.C. Penny were sealed, low maintenance type lead-acid batteries with lead-calcium grids. The fourth candidate ESB WILLARD was a vented charge retaining lead-acid battery constructed with high purity thick lead grids. The fifth candidate secondary battery was a pocket plate type nickel-cadmium battery NIFE. Tests were also performed on cycled ESB-WILLARD batteries that had been operated seven years in solar photovoltaic power systems. Equilibrium voltage measurements at two temperatures -20C, 50C for various charge rates at 80, 90 and 100 state-of-charge were completed on all batteries. This information can be used to set voltage regulation points and temperature compensation coefficients for each battery. Failure analysis of the batteries cycled seven years in photovoltaic power systems revealed moderate sulfation of the negative plates and a moderate amount of sediment in the bottom of the battery case. Three to five additional years of cycling is estimated for these batteries. The nickel-cadmium batteries do not appear to be suitable for this application due to their low charge efficiency at low charge rates.