The chemical action that takes place in a secondary cell affects both the electrode material
and the composition of liquid electrolyte, as shown below.
The transfer of materials in the cell above causes the sponge lead and lead peroxide to
change to lead sulfate. Drawing (D) shows a generator being used to force current through
the cell in a direction opposite to the direction of current in drawing (B); therefore, the
generator is charging the cell. The electrolyte in drawing (C) is mostly water. (H2O).