- Charge equalization is an important part of the charge process for series-connected battery cells. This paper reviews battery behavior and performance related to the equalization problem, in the context of vavle-regulated lead-acid batteries. As established in prior work, equalization precision on the order of 10 mV/cell is required for a successful process. Equalization processes that can achieve this precision do indeed extend the life of battery packs. Active equalization speeds the process and supports exchange of a single failed cell or monoblock Passive equalization (conventional overcharge) is too slow in most contexts for strings longer than about 12 cells. Active equalization provides clear life advantages over other approaches. The results are consistent with the hypothesis that a properly designed active equalization process can provide battery cycle life for a series string that matches the cycle operating results for an individual cell.