The battery operation
The automotive battery supplies electric current to operate the starting motor and ignition system while starting the engine. It also acts as a voltage stabilizer by supplying current for the lights, radio and other electrical accessories when the alternator is not handling the load. In addition, the battery supplies a small current to the volatile memory in the electronic control module (ECM) while the ignition key is off.
Chemical in battery
the battery is a lead-acid storage battery. the chemicals in it are sponge lead(a solid), lead peroxide (a paste), and sulfuric acid (a liquid). these three substances can react chemically to produce a flow of current. the lead peroxide and sponge lead are held in plate grinds to form the positive and negative plates. the grinds are made of lead with other elements, such as calcium added.
The sulfuric acid is miced with water to form the electrolyte. this is the liquid in a battery. the electrolyte is about 60 percent water and 40 percent sulfuric acid in fully-charged battery. As the battery discharges, the electrolyte loses sulfuric acid and becomes mostly water.
Battery construction
The battery case is molded plastic. the plates are welded to plate straps to form plates groups. to make a battery cell , a positive plate group fits into a negative plate group. porous separator are placed between the plates. this prevent positive and negative plates from touching while allowing electrolyte to circulate between the plates
The assembly of plate groups and separator is an element. the elements fit into compartments in the battery case to form cell. heavy lead connectors attach to the terminal and connect the cells in series. a plastic cover form the top of the battery. some batteries have openings in the cover from which filler plugs or event caps are removed to add water maitenance-free batteries do not have the removable vent caps.
Some batteries are hold-terminal batteries. they have the two main terminals or pots in the cover. the positive post is large than the negative terminal post. other batteries are side-terminal batteries. they have the terminals on the side of the battery.
Connecting Cells
The 12-volts battery has six cells connected in series. this means the cell voltages add together to produce the battery voltage. each cell has a voltage of about 2.15 volts at full charge. A fully charge battery has a voltage of about 12.9 volts.
