is a three-stage charging procedure for lead–acid batteries. A lead–acid battery's nominal voltage is 2.2 V for each cell. For a single cell, the voltage can range from 1.8 V loaded at full discharge, to 2.10 V in an open circuit at full charge. varies depending on battery type (flooded cells, gelled electrolyte, ), and ranges from 1.8 V to 2.27 V. Equalization voltage, and charging voltage for sulfated c. During discharge, sulfur from the sulfuric acid combines with lead to form lead sulfate while hydrogen combines with oxygen released at the positive plate to form water. This is given the formula below: During charging, the reverse happens. The charge current causes the lead sulfate to dissociate The sulfate in lead sulfate. As the battery charging nears completion, the charge current is usually higher than the current required to break the remaining lead sulfate on the plates. Though hydrogen and oxygen gases are not as dangerous to breathe as hydrogen sulfide and sulfur dioxide gas, they are nevertheless dangerous in high concentrations as they can cause a fire. In all cases, the use of the right battery charger while charging the.