5.2.1 Voltage of lead acid battery upon charging. The charging reaction converts the lead sulfate at the negative electrode to lead. At the positive terminal the reaction converts the lead to lead oxide. As a by-product of this reaction, hydrogen is evolved.
A lead acid battery consists of electrodes of lead oxide and lead are immersed in a solution of weak sulfuric acid. Potential problems encountered in lead acid batteries include: Gassing: Evolution of hydrogen and oxygen gas. Gassing of the battery leads to safety problems and to water loss from the electrolyte.
Potential problems encountered in lead acid batteries include: Gassing: Evolution of hydrogen and oxygen gas. Gassing of the battery leads to safety problems and to water loss from the electrolyte. The water loss increases the maintenance requirements of the battery since the water must periodically be checked and replaced.
The following graph shows the evolution of battery function as number of cycles and depth of discharge for a shallow-cycle lead acid battery. A deep-cycle lead acid battery should be able to maintain a cycle life of more than 1,000 even at DOD over 50%.
Wide differences in cycle performance may be experienced with two types of deep cycle batteries and therefore the cycle life and DOD of various deep-cycle batteries should be compared. A lead acid battery consists of electrodes of lead oxide and lead are immersed in a solution of weak sulfuric acid.
However, due to the corrosive nature the elecrolyte, all batteries to some extent introduce an additional maintenance component into a PV system. Lead acid batteries typically have coulombic efficiencies of 85% and energy efficiencies in the order of 70%.