Fig. 69.—Two Methods of Connecting Cells so as to obtain Different Voltage and Amperage Values.
Storage batteries are made up of plates of lead (the electrodes) or an alloy of lead cast into a "grid" or framework.
The framework may be one of a large number of patterns, but usually consists of a set of bars crossing one another at right angles, leaving a space between.
The spaces are filled with a paste of lead oxide. They are then "formed" by placing in a tank of acid solution and connected to a source of electric current.
Fig. 70.—Small Storage Cells.
The plate connected to the positive wire gradually turns dark-brown in color, due to the changes in the paste, which gradually turns into lead peroxide. The paste in the negative plate becomes gray in color and changes into a form of metallic lead called spongy lead.
The positive and negative plates are placed in a bundle after the forming process has been completed. They are kept apart by strips of wood or rubber called separators.
The negative plates of one cell are all connected in parallel at one end of the cell. The positive plates are connected at the other end. The liquid surrounding the plates is diluted sulphuric acid.
When the battery has been exhausted, it is charged by connecting a dynamo with the terminals of the battery and sending a current through it. This current reverses the chemical action, which goes on during the discharge of the battery.