The depth of discharge in conjunction with the battery capacity is a fundamental parameter in the design of a battery bank for a PV system, as the energy which can be extracted from the battery is found by multiplying the battery capacity by the depth of discharge. Batteries are rated either as deep-cycle or shallow-cycle. Over time, battery capacity degrades due to sulfation of the battery and shedding of active material. The degradation of battery capacity depends most strongly on the interrelationship between the following parameters: 1. the. The production and escape of hydrogen and oxygen gas from a battery cause water loss and water must be regularly replaced in lead acid batteries. Other components of a battery system do not require maintenance as. Lead acid batteries typically have coloumbic efficiencies of 85% and energy efficiencies in the order of 70%. Depending on which one of the above problems is of most concern for a particular application, appropriate modifications to the basic battery configuration improve battery performance. For. The lead–acid cell can be demonstrated using sheet lead plates for the two electrodes. However, such a construction produces only around one ampere for roughly postcard-sized plates, and for only a few minutes. Gaston Planté found a way to provide a much larger effective surface area. In Planté's design, the positive and negative plates were formed of two spirals o.