Comments on the evaluation of valve regulated lead-acid batteries (VRLA) under deep cycling regimes

The evaluation of components, orientation and materials for recombinant valve regulated lead-acid batteries is a challenging and enlightening task. The selection of an appropriate charging regime is critical to the meaningful evaluation of materials, designs and applications. Included in the authors´ studies were measurements of discharge capacity, impedance, weight loss, open circuit voltage after float effects of stack compression and variations of charging regime. Tear-down analysis of cells provided information on electrolyte distribution and concentration. Chemical and thermal analyses of the active materials provided information on sulfation. Electrical testing data highlighted the sensitivity of cycle life performance to even a small mismatch of series connected cells under deep cycling conditions. The results support earlier work indicating the advantages of horizontal oriented cell testing and emphasize the need for closely matched cells for testing of VRLA cells