THE HISTORY OF BATTERIES

Battery development dates as far back as the late 18th century. The cause was championed by the work carried out by Luigi Galvani from 1780 to 1786. Through his experiments Galvani observed that, when connected pieces of iron and brass were applied to frog’s legs, they caused them to twitch. However, Galvani thought that the effect originated in the leg tissue. Nevertheless, Galvani had laid the cornerstone for further developments in "voltaic" electricity.

From 1796 - 1799, Alessandro Volta experimented with zinc and silver plates to produce electric currents at the Pavia University. Volta stacked the two to form a "pile", the first "dry" battery. By 1800 Volta had created the "crown of cups", a modified arrangement of zinc and silver discs dipped in a salt

In the years that ensued, other means of producing electricity were invented, all of which involved the use of liquid electrodes. Those developed by Bunsen (1842) and Grove (1839) were amongst the most successful systems, and, were used for many years.

By 1866, Georges Leclanche, a French engineer, patented a new system, which was immediately successful. In the space of two years, twenty thousand of his cells were being used in the telegraph system. Leclanche's original cell was assembled in a porous pot. The positive electrode consisted of crushed manganese dioxide with a little carbon mixed in. The negative pole was a zinc rod. The cathode was packed into the pot, and a carbon rod was inserted to act as a currency collector. The anode or zinc rod and the pot were then immersed in an ammonium chloride solution. The liquid acted as the electrolyte, readily seeping through the porous cup and making contact with the cathode material. Leclanche's "wet"cell (as it was popularly referred to) became the forerunner to the world's first widely used battery, the zinc carbon cell.

Leclanche's invention, which was quite heavy and prone to breakage, was steadily improved over the years. The idea of encapsulating both the negative electrode and porous pot into a zinc cup was first patented by J.A. Thiebaut in 1881. But, it was Carl Gassner of Mainz who is credited as constructing the first commercially successful "dry" cell. Variations followed. By 1889 there were at least six well-known dry batteries in circulation. Later battery manufacturing produced smaller, lighter batteries, and the application of the tungsten filament in 1909 created the impetus to develop batteries for use in torches.

The production of batteries was greatly increased during the First World War as a means of powering torches, field radios. Other milestones in battery production include the widespread radio broadcasting, which brought battery-operated wireless into the heart of many homes. But, it was during the inter-war years that battery performance was greatly enhanced. This was achieved through better selection of materials and methods of manufacture.

Batteries have now become an essential part of everyday life. They are the power source for millions of consumer, business, medical, military and industrial appliances worldwide. This demand is growing.

WHAT IS A BATTERY ?

Batteries are the power behind much of our everyday life from calculators and camcorders to watch and walkmans.

Batteries are electrochemical cells that store energy for release on demand when a switch is flipped or a circuit is closed. Individual cells are typically 1.5 volts and these can be connected together to produce batteries of a higher voltage. For example, inside the common 9 volt battery are six 1.5 volt cells connected in series.

A galvanic cell also needs two substances for energy conversion, represented by two electrochemically active electrodes of different composition, both of which are immersed in an electrolyte which provides a conductive medium between them.

One of the electrodes uses a metal such as zinc or lithium. Within the electrolyte it establishes a negative potential and consequently represents the negative electrode. The other electrode consists of an electron conducting compound which is rich in oxygen, e.g. manganese dioxide, silver oxide, nickel hydroxide or atmospheric oxygen in combination with a suitable oxygen electrode. This electrode establishes a positive potential within the electrolyte and consequently represents the positive electrode of the electrochemical system. Depending on the electrochemical system, the cell voltage will be between 1.2 V and 4 V. When connecting the system to an external load, electrical energy will be taken out of the system, while the chemical energy stored inside the cell or battery will be used up.

Non rechargeable batteries are often called "primary batteries" because they are the primary source of electricity, are not meant to be recharged and have a definite use life after which they are discarded. Rechargeable batteries are sometimes called "secondary batteries" because their power is derived from a secondary source – the mains.

HOW A BATTERY IS MADE ?

Batteries are made of five basic components :

• A resilient plastic container.

• Positive and negative internal plates made of lead.

• Plate separators made of porous synthetic material.

• Electrolyte, a dilute solution of sulfuric acid and water, better known as battery acid.

• Lead terminals, the connection point between the battery and whatever it powers.

The manufacturing process begins with the production of a plastic container and cover. Most automotive battery containers and their covers are made of polypropylene. For a typical 12-volt car battery, the case is divided into six sections, or cells, shaped somewhat like one row in an ice-cube tray. The cover is dropped on and sealed when the battery is finished.

The process continues with the manufacture of grids or plates from lead or an alloy of lead and other metals. A battery must have positive and negative plates to conduct a charge.

Next, a paste mixture of lead oxide -- which is powdered lead and other materials -- sulfuric acid and water is applied to the grids. Expander material made of powdered sulfates is added to the paste to produce negative plates. Inside the battery, the pasted positive and negative plates must be separated to prevent short circuits. Separators are thin sheets of porous, insulating material used as spacers between the positive and negative plates. Fine pores in the separators allow electrical current to flow between the plates while preventing short circuits

In the next step, a positive plate is paired with a negative plate and a separator. This unit is called an element, and there is one element per battery cell, or compartment in the container. Elements are dropped into the cells in the battery case. The cells are connected with a metal that conducts electricity. The lead terminals, or posts, are then welded on. The battery is then filled with electrolyte - or battery acid -- a mixture of sulfuric acid and water, and the cover is attached. The battery is checked for leaks.

The final step is charging, or finishing. During this step, the battery terminals are connected to a source of electricity and the battery is charged for many hours. When the battery is fully charged, it moves to another line where the case is cleaned, if necessary, and the labels are attached.