Battery element
Battery case, cover, and caps
Battery terminals
Electrolyte

BATTERY ELEMENT.- The battery element is made up of negative plates, positive plates, separators, and straps (fig. 2-3). The element fits into a cell compartment in the battery case. Most automotive batteries have six elements.

Figure 2-3.- Battery element.

Each cell compartment contains two kinds of chemically active lead plates, known as positive and negative plates. The battery plates are made of GRID (stiff mesh framework) coated with porous lead. These plates are insulated from each other by suitable separators and are submerged in a sulfuric acid solution (electrolyte).

Charged negative plates contain spongy (porous) lead (Pb) which is gray in color. Charged positive plates contain lead peroxide (PbO2 ) which has a chocolate brown color. These substances are known as the active materials of the plates. Calcium or antimony is normally added to the lead to increase battery performance and to decrease gassing (acid fumes formed during chemical reaction). Since the lead on the plates is porous like a sponge, the battery acid easily penetrates into the material. This aids the chemical reaction and the production of electricity.

Lead battery straps or connectors run along the upper portion of the case to connect the plates. The battery terminals (post or side terminals) are constructed as part of one end of each strap.

To prevent the plates from touching each other and causing a short circuit, sheets of insulating material (microporous rubber, fibrous glass, or plastic-impregnated material), called separators, are inserted between the plates. These separators are thin and porous so the electrolyte will flow easily between the plates. The side of the separator that is placed against the positive plate is grooved so the gas that forms during charging will rise to the surface more readily. These grooves also provide room for any material that flakes from the plates to drop to the sediment space below.