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| Function.. |

| A storage battery is a device that may be used repeatedly for storing electrical energy at one time for use at another. It does not directly store electrical energy as such, although energy is put into it in the form of direct-current electricity. Rather, this energy is stored as chemical energy by means of a chemical process. By a reversal of this process, the chemical energy is converted back to direct-current electrical energy and delivered for utilization in this form. The process of putting energy into the battery is termed charging and of delivering energy, discharging. |

| Principle of Operation |

| A storage battery consists of one or more cells connected in series, each cell having two plates (one positive, the other negative) immersed in a solution called the electrolyte (Fig. 15-1). When the battery discharges, the chemical composition of these three elements change; when it charges, they are restored to their original condition. The chemical reactions that take place are different for different types of batteries. |

| The most frequently used type of battery is the lead-sulphuric-acid (or simply lead) storage battery, principally because of its economic advantages. Another common type of battery is the nickel-iron-alkaline battery, or so- |

| Figure 15-1 Basic cell and battery: (A) Simple cells, (B) symbol of one cell, (C) battery of four cells in series, and (D) symbol of multicell battery. |

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