A battery converts chemical energy to electrical energy. This conversion enables
electrical power to be stored.
STATE the purpose of a battery.
DESCRIBE the operation of a simple voltaic cell.
STATE the chemical equation for the reaction
that occurs when a lead-acid battery is being
charged or discharged.
EXPLAIN the relationship between specific
gravity and state of charge of a lead-acid battery.
The purpose of a battery is to store chemical energy and to convert this chemical energy into
electrical energy when the need arises.
As described in previous chapters, a chemical cell (or voltaic cell) consists of two electrodes of
different types of metals or metallic compounds and an electrolyte solution which is capable of
conducting an electric current.
A good example of a voltaic cell is one that contains zinc and copper electrodes. The zinc
electrode contains an abundance of negatively charged atoms, and the copper electrode contains
an abundance of positively charged atoms. When these electrodes are immersed in an electrolyte,
chemical action begins. The zinc electrode will accumulate a much larger negative charge
because it dissolves into the electrolyte. The atoms, which leave the zinc electrode, are positively
charged and are attracted by the negatively charged ions of the electrolyte; the atoms repel the
positively charged ions of the electrolyte toward the copper electrode (Figure 2).