The conventional battery is constructed of seven basic components:
- Positive plates.
- Negative plates.
- Plate straps.
The difference between “3-year” and “5-year” batteries is the quantity of material expanders used in the construction of the plates and the number of plates used to build a cell. Material expanders are fillers that can be used in place of the active materials. They are used to keep the manufacturing costs low.
FIGURE. Conventional battery grid.
A plate, either positive or negative, starts with a grid. Grids are generally made of lead alloys, usually antimony. About 5% to 6% antimony is added to increase the strength of the grid. The grid is the frame structure with connector tabs at the top. The grid has horizontal and vertical grid bars that intersect at right angles. An active material made from ground lead oxide, acid, and material expanders is pressed into the grid in paste form. The positive plate is given a “forming charge” that converts the lead oxide paste into lead peroxide. The negative plate is given a “forming charge” that converts the paste into sponge lead.
FIGURE. A battery cell consists of alternate positive and negative plates.
The negative and positive plates are arranged alternately in each cell element. Each cell element can consist of 9 to 13 plates. The positive and negative plates are insulated from each other by separators made of microporous materials. The construction of the element is completed when all of the positive plates are connected to each other and all of the negative plates are connected to each other. The connection of the plates is by plate straps.
FIGURE. Construction of a battery element.
A typical 12-volt automotive battery is made up of six cells connected in series. This means the positive side of a cell element is connected to the negative side of the next cell element. This is repeated throughout all six cells. By connecting the cells in series, the current capacity of the cell and cell voltage remain the same. The six cells produce 2.1 volts each. Wiring the cells in series produces the 12.6 volts required by the automotive electrical system. The plate straps provide a positive cell connection and a negative cell connection. The cell connection may be one of three types: through the partition, over the partition, or external. The cell elements are submerged in a cell case filled with electrolyte solution. Electrolyte consists of sulfuric acid diluted with water. The electrolyte solution used in automotive batteries consists of 64% water and 36% sulfuric acid, by weight. Electrolyte is both conductive and reactive.
FIGURE. The 12-volt battery consists of six 2-volt cells that are wired in series.
FIGURE. The cell elements can be connected using one of three intercell connection methods.
The battery case is made of polypropylene, hard rubber, and plastic base materials. The battery case must be capable of withstanding temperature extremes, vibration, and acid absorption. The cell elements sit on raised supports in the bottom of the case. By raising the cells, chambers are formed at the bottom of the case that trap the sediment that flakesoff the plates. If the sediment was not contained in these chambers, it could cause a conductive connection across the plates and short the cell. The case is fitted with a one-piece cover.
Because the conventional battery releases hydrogen gas when it is being charged, the case cover will have vents. The vents are located in the cell caps of a conventional battery.
FIGURE. The vents of a conventional battery allow the release of gases.