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Monday, May 31, 2010

Lead-acid storage battery

History of Lead Acid Battery

The lead-acid storage battery, an important energy storage device, is the most widely used secondary storage cell by automobile and other industries. Storage cells are devices which release a flow of electron through an external circuit as a result of reactions occurring between the active electrode materials and ions transported by the electrolyte. The cells in which the reactions are reversible are called secondary cells. In these cells the active materials can be returned to their original state by applying electrical current from an external source in the opposite direction to the flow of the cells discharge current.

In the early nineteenth century, scientists discovered that when direct current was passed between some pairs of electrodes of the same metal immersed in an electrolyte, the electrodes became polarized, i.e. when the circuit was opened a difference of potential existed between the electrodes. If they were connector, together a current flowed. Based on these experiments, in 1959
Gasten Plant began to investigate such cell using two electrodes immersed in dilute sulfuric acid. He found that appreciable currents could be obtained from the cell, after it was charged to produce a coating of lead peroxide on the positive plate. This was a major breakthrough in the field of electro chemistry.
Since then major developments have taken place in basic material of construction of lead-acid batteries. The present construction of this type of battery consists of positive electrode made up of leap peroxide, negative electrodes of lead in highly active metallic sponge. The insulating layers are made of hard rubber, PVC etc. The electrolyte is a dilute aqueous solution of sulphuric acid and container is marie of plastic, glass, rubber or polypropylene.

In 1940's six volt rubber case, featuring external cell connectors were available. Ford company offered codar separators and thirteen percent (13%) antimony grid alloys. The battery had a temperature compensating,vibrating contact voltage regulator. By the end of the 50's twelve volt battery was available featuring rubber separators and seven percent antimony in the grid alloy.
Towards the end of the 60's, the typical new car battery featured, through partition connectors, one piece cover, and sealed side terminals, a rubber container and grid alloy containing four percent antimony. Some of the leading battery manufacturers also introduced polypropylene containers at that time.

During the latter half of 70's the battery industry entered the maintenance free era. Grids with 1-2% antimony and other alloya like Ca, sn and plates made by high speed continuous strip processing equipment were introduced. In place of conventional separators plates, encapsulated in plastic envelopes came as new technology. The polypropylene container became a cocoon, completely sealing the battery against entry and containing subsystems, such as build-in state of charge indicators, and flame arresting vent system. In early 80's major changes tookplace in the technology of manufacturing systems, like continuous automatically controlled casting, rolling,grid expansion, pasting, curing cutting and stacking of battery plates.. This enhanced the roduction rates to a level undreamed of ten years earlier. In the modern plants up above the plate line, active material ingredients are programmed, weighed, and blended by computer controlled paste mixers, resulting in control of plate weight, thickness and chemistry, which was not possible few years ago. Control of this production system is backed up by analytical equipment, such as the atomic absorption spectrograph, florescent xray spectrometers, particle distribution counter and optical emission spectrograph. Sophisticated welding machines are common in all battery plants in USA, UK, Canada and France.

At present a great deal of emphasis is on the need of smaller and lighter batteries, for new small sized car and automobiles. The drive for improved fuel economy and the space limitations of present and planned engine compartments, are still strong factors today for the development of small, light weight, high powered batteries.

Chemical Reaction
Batteries use a chemical reaction to do work on charge and produce a voltage between their output terminals.

The reaction of lead and lead oxide with the sulfuric acid electrolyte produces a voltage. The supplying of energy to and external resistance discharges the battery.
The discharge reaction can be reversed by applying a voltage from a charging source.
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