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BATTERY

BATTERY
 
The battery is the storehouse of power. The battery stores energy that is chemical and gives it out in the form of electrical energy. Alessandro Volta, an Italian physicist in 1800, kicked off the age of modern batteries. A battery is a series of connected voltaic cells. The statistics as of 2005 is that the battery industry generates $48 billion in annual sales. 
The earliest type of battery was used in ancient times and was known as the Baghdad Battery. It dates back to 250 BC or 640AD. The electrical function is not clear and the question remains that were these at all batteries?  But the name is stuck and historians continue to argue. The earliest use of Batteries was in medicine and in electroplating of jewellery.

In the late 18th century Luigi Galvani referred to it as ‘animal electricity’. By connecting two dissimilar metals he created an electric current. One metal touched the leg of a frog and the other had contact with both animal and metal. This created a closed circuit. Thus the leg of the frog served the purpose of both electrolyte and detector. The metals were the electrodes. Galvani was surprised to notice that even after the death of the frog, its legs would jerk when coming in contact with the metals.
In 1791 Volta, replaced the animal by a cardboard that had been soaked in saline water. His experiments enabled him to measure force of electric movement, which came to be named after him – voltage. The device was named voltaic cell or just cell. By placing galvanic cells in a series Voltas is credited with the invention of the first modern battery. Initially the cells were actually piled over one another. This pile gave out greatly increased emf  – 32 piles gave out 50 volts. Europe still continues to use the word ‘piles’ for batteries. Volta made the mistake of not understanding the chemical reactions. He was under the impression that the source of power from the cells did not have limits. He thought that that the chemical results were just a nuisance. It was for Michael Faraday to show, in and about 1830 that this was actually an inevitable byproduct of the exercise.
The research continued and later scientists placed the cells in series. These banks came to be termed batteries. Previously Benjamin Franklin had used this word in reference to Leyden jars or capacitors kept in series. The first batteries were useful for experiments but not for practical purposes as the current were not regular. Daniell cell in 1836 was the answer for more dependable current. It came to be adapted for industrial use in devices that were stationary – especially for telegraph works. At that time electrical distribution systems were non-existent. The newcomers were clumsy, prone to leaks and spills if not carefully handled. It was not suitable for portable purposes. Glass jars were in use. This made the whole contraption very fragile and delicate. Dry cell batteries made its debut towards the end of the 19th century and the practical side got a great boost. 
The work of a battery is to convert chemical energy directly into an electrical one. In it are either one or more voltaic cells. Each of the latter has two half-cells, which are connected in series by means of a conductive electrolyte. The cells have electrodes and anodes – positive and negative respectively. They touch each other through a solid or liquid substance called electrolyte, in which these are submerged. The cells are kept in a container. There is a separator between the two to prevent them from touching each other. With each half-cell having a net emf, the net emf of the battery is the difference between the two. Terminal voltage is the electrical potential difference of the terminals. The voltage is dependent on the chemicals that are used and the level of their concentrations. 
Batteries are broadly speaking divided into two groups – primary and secondary. The former changes irreversibly chemical into electrical energy. Once the supply is exhausted energy cannot be restored. But a process involving reversing the electrical energies to their original constituents can recharge the secondary type of batteries.
The greater the electrolyte and electrode materials the more is cell capacity. Larger cells have thus greater capacity. The capacity of batteries depends on the scale of current, the time it stays, the terminable voltage that is allowable, the temperature etc.
Even in a packed condition batteries may lose about a quarter of their charge annually. It is known as the phenomenon of self-discharge. Some gets damaged in frozen conditions or when the temperature sharply fluctuates. Special reserve batteries meant for long storage are very costly to manufacture. 
It is now 250 years since batteries have hit the scene. Its manufacture is very costly and it consumes some of the most toxic materials. Thus the process of recycling has been introduced. If swallowed, batteries can be lethal. Also batteries left battered will emit hazardous stuff like lead, mercury etc. into the environment.
Battery’s often explode. This is because of misuse of the battery like trying to recharge a non-chargeable model. Explosions happen more often in the case of car batteries when a short circuit leads to the generation of large amounts of currents. Moreover car batteries emit hydrogen when it is overcharged, Overcharging however is negligible and the gas produced quickly gets dissipated. Occasionally when batteries fail because of blockage, the pressure inside the cells rapidly increases and a big explosion takes place. Overcharging a battery beyond its normal capacity may lead to an explosion. This causes irreparable damage to the set. 
Today the shelves are replete with many kinds of batteries – handheld ham radio battery, a camcorder battery, battery for cordless phones, button cell batteries etc.
The modern user can avail of two types of batteries – the disposable variety and the rechargeable models. Disposable ones are used in devices that are mobile and portable, that due not use much current and are not used regularly or used a distance away from alternative source of power.  The application of electric current can revitalize rechargeable batteries. The tools used to do so are termed chargers.
Disposable batteries are of many varieties – zinc carbon batteries, zinc chloride batteries, alkaline batteries, silver oxide batteries, lithium iron disulphide batteries, mercury batteries, nickel oxyhydroxide batteries, water activated batteries, zinc air battery and thermal battery.
There is a constant growing demand for rechargeable batteries or secondary batteries. Flow batteries are very powerful and used for maritime purpose. Submarines use the maximum number of batteries.  In toyshops enterprising children can pick up step-by-step instructions with materials for making home made batteries. Traction batteries are highly powered and used to move vehicles like electric cars. 
To give the finishing touches to the story on batteries let us turn to the source of all dynamism – Nature. The earth gives the golden harvest, then rests as it recharges ready to dance in spring, receive the rains and sprout again with dizzy frenzy of colour and splash. The human body too ticks and then as it rests the entire system goes into action to replenish and reinvigorate for the coming of a new day.