<Dd> Pb (s) + PbO (s) + 2H SO (aq) → 2PbSO (s) + 2H O (l) </Dd> <P> The sum of the molecular masses of the reactants is 642.6 g / mol, so theoretically a cell can produce two faradays of charge (192,971 coulombs) from 642.6 g of reactants, or 83.4 ampere - hours per kilogram (or 13.9 ampere - hours per kilogram for a 12 - volt battery). For a 2 volts cell, this comes to 167 watt - hours per kilogram of reactants, but a lead--acid cell in practice gives only 30--40 watt - hours per kilogram of battery, due to the mass of the water and other constituent parts...</P> <P> In the fully charged state, the negative plate consists of lead, and the positive plate lead dioxide, with the electrolyte of concentrated sulfuric acid . </P> <P> Overcharging with high charging voltages generates oxygen and hydrogen gas by electrolysis of water, which is lost to the cell . The design of some types of lead - acid battery allow the electrolyte level to be inspected and topped up with any water that has been lost . </P>

The negative plate of a lead acid battery is made of