Battery (electricity)

In science and technology, a battery is a device that stores energy and makes it available in an electrical form. Although such storage in an electrostatic form is practical in some specialized uses, batteries are usually electrochemical devices.

In a technical sense, the distinction may be made between

  • an electrical battery, an electrical energy storage device composed of similar (usually identical) parts that are "wired together" (i.e., interconnected with electrical conductors), and
  • an electrical cell, a single such unit, possibly one of cell in a (strict-terminology) battery of multiple cells.
That distinction, however, is pedantic in most contexts (other than the expression "dry cell"), and it is more normal to call a single cell "a battery" than "a cell".

Table of contents
1 History
2 The Future
3 Electrical Component
4 Common battery types
5 External Links

History

There is some evidence, in the form of the Baghdad Battery from around 200 BC, and possibly related artifacts in ancient Egypt, of primary cells having been used in ancient times in electroplating as a means of precious-metal gilding. In any case, however, any such knowledge was a "dead end" in the history of electricity, and bear no relationship to the development of modern batteries.

In 1748, Benjamin Franklin coined the term battery to describe an array of charged glass plates. He adapted the word from its earlier sense meaning a beating, which is what an electric shock from the apparatus felt like. In those days, the entertaining effect of an electric shock was one of the few uses of the technology. Other experimenters made batteries from a number of Leyden jars connected in parallel. The definition was later widened to include an array of electrochemical cells or capacitors. The chemical battery was the Voltaic pile rediscovered by Alessandra Cont di Volta in 1800. Alessandro Volta researched the effects which different metals produced when exposed to salt water. In 1801, Volta demonstrated the Voltaic cell to Napoleon Bonaparte. Luigi Galvani researched the same effect with two pieces of the same metal exposed to salt water.

The scientific community at this time called these batteries piles. The battery was called an accumulator, because it held charge, or an artificial electrical organ. Some researchers called the battery a gravity cell because gravity kept the two sulfates separated. The name crowfoot cell was also commonly used because of the shape of the zinc electrode used in the batteries.

In 1800, William Nicholson and Anthony Carlisle used a battery to decompose water into hydrogen and oxygen. Sir Humphry Davy researched this chemical effect at the same time. Davy researched the decomposition of substances (called electrolysis). In 1813, he constructed a 2,000-plate paired battery in the basement of Britain's Royal Society, covering 889 square feet. Through this experiment, Davy deduced that electrolysis was the action in the voltaic pile that produced electricity. In 1820, the British resercher John Frederic Daniell improved the voltaic cell. The Daniell cell consisted of copper and zinc plates and copper and zinc sulphates. It was used to operate telegraphs and doorbells. Between 1832 and 1834, Michael Faraday conducted experiments with a ferrite ring, a galvanometer, and a connected battery. When the battery was connected or disconnected, the galvanometer deflected. Faraday also developed the priciple of ionic mobility in chemical reactions of batteries. In 1839, William Robert Grove developed the first fuel cell, which produced electrical energy by combining hydrogen and oxygen. Grove developed another form the electric cell using zinc and platinum electrodes. These electrodes were exposed to two acids separated by a diaphragm.In the 1860s, Georges Leclanché of France developed a carbon-zinc battery. It was a wet cell, with electrodes plunged into a body of electrolyte fluid. It was rugged, manufactured easily, and had a decent shelf life. An improved version called a dry cell was later made by sealing the cell and changing the fluid electrolyte to a wet paste. The Leclanché cell is a type of primary (non-rechargeable) battery. In the 1860s, Raymond Gaston Plant invented the lead-acid battery. He immersed two thin solid lead plates separated by rubber sheets in a dilute sulfuric acid solution to make a secondary (rechargeable) battery. The original invention had a short shelf life, though. Around 1881, Emile Alphonse Faure, with his colleagues, developed batteries using a mixture of lead oxides for the positive plate electrolyte. These had faster reactions and higher efficiency. In 1878, the air cell battery was developed. In 1897, Nikola Tesla researched a lightweight carbide cell and a oxygen-hydrogen storage cell.

In 1900, Thomas Edison developed the nickel storage battery. In 1905, Edison developed the nickel-iron battery. Like all electrochemical cells, Edison's produced a current of electrons that flowed only in one direction, known as direct current. In World War II, Samuel Ruben and Philip Rogers Mallory developed the mercury cell. In 1949, Lew Urry developed the small alkaline battery at the Eveready Battery Company laboratory in Parma, Ohio. In the 1950s, Russell S. Ohl developes a wafer of silicon that produced free electrons. In the 1950s, Ruben improved the alkaline manganese battery. In 1954, Gerald L. Pearson, Daryl M. Chapin, and Calvin S. Fuller produced an array of several such wafers, making the first solar battery or solar cell. In 1956, Francis Thomas Bacon developed the hydrogen-oxygen fuel cell. In the 1960s, German researchers invented a gel-type electrolyte lead-acid battery. Duracell was formed in 1964.

The Future

Initial research indicates that nanotechnology batteries employing carbon nanotubes will have twice the life of traditional modern batteries.

Electrical Component

The cells in a battery can be connected in parallel or in series, or both. A parallel combination of cells has the same voltage as a single cell, but can supply a higher current (the sum of the currents from all the cells). On the other hand, a series combination has the same current rating as a single cell but its voltage is the sum of the voltages of all the cells. Most practical electrochemical batteries, such as 9 volt flashlight (torch) batteries and 12 V automobile (car) batteries, have a series structure. In both types, the energy stored in the battery is equal to the sum of the energies stored in all the cells.

A battery can be modelled as a perfect voltage source (i.e. one with zero internal resistance) in series with a resistor. The voltage source depends mainly on the chemistry of the battery, not on whether it is empty or full. When a battery runs down, its internal resistance increases. When the battery is connected to a load (e.g. a light bulb), which has its own resistance, the resulting voltage across the load depends on the ratio of the battery's internal resistance to the resistance of the load. When the battery is fresh, its internal resistance is low, so the voltage across the load is almost equal to that of the battery's internal voltage source. As the battery runs down and its internal resistance increases, the proportion of its internal voltage that gets through the internal resistance to appear at the load gets smaller, so the battery's ability to deliver power to the load decreases.

Common battery types

From a user's viewpoint, at least, batteries can be generally divided into two main types - rechargeable and non-rechargeable (disposable). Each is in wide usage.

Disposable batteries, also called primary cells, are intended to be used once, until the chemical changes that induce the electrical current supply are complete, at which point the battery is discarded. These are most commonly used in smaller, portable devices with either low current drain, only used intermittently, or used well away from an alternative power source. (see also waste).

Rechargeable batteries or secondary cells, by contrast, after being drained can be re-used. This is done by applying externally supplied electrical current which causes the chemical changes that occur in use to be reversed. Devices to supply the appropriate current are called chargers or rechargers.

The oldest form of rechargeable battery still in modern usage is the lead-acid battery. This battery is notable in that it contains a liquid in an unsealed container, requiring that the battery be kept upright and the area be well-ventilated to deal with the explosive oxygen and hydrogen gases which are vented by these batteries during overcharging. The lead-acid battery is also very heavy for the amount of electrical energy it can supply. Despite this, its low manufacturing cost and its high surge current levels make its use common where the weight and ease of handling are not concerns.

A common form of lead-acid battery is the modern car battery. This can deliver about 10,000 watts of power at a nominal 12 volts (although the true open-circuit voltage is closer to 13.7V) and has a peak current output that varies from 450 to 1100 amperes. The battery's electrolyte is sulphuric acid, which can cause serious injury if splashed on the skin or eyes.

A more expensive type of lead-acid battery called a gel battery (or "gel cell") contains a semi-solid electrolyte to prevent spillage. More portable rechargeable batteries include several "dry cell" types, which are sealed units and are therefore useful in appliances like mobile phones and laptops. Cells of this type (in order of increasing power density and cost) include nickel-cadmium (nicad or NiCd), nickel metal hydride (NiMH), and lithium-ion (Li-Ion) cells.

Disposable cells come in a number of standard sizes, so the same battery type can be used in a wide variety of appliances. Some of the major types used in portable appliances are listed below:

USIECOtherShapeVoltage
N LR1cylinder L 30.2 mm, D 12 mm 1.5 V
AAAA  cylinder L 42 mm, D 8 mm 1.5 V
AAAR03LR03,MN2400,AM4,UM4,HP16,microcylinder L 44.5 mm, D 10.5 mm 1.5 V
AAR6LR6,MN1500,AM3,UM3,HP7,mignoncylinder L 50 mm, D 14.2 mm1.5 V
CR14LR14,UM2,MN1400,HP11,babycylinder L 43 mm, D 23 mm1.5 V
DR20LR20,MN1300,UM1,HP2,monocylinder L 58 mm, D 33 mm1.5 V
PP36F226R61,MN1604rectangular prism 48 mm x 25 mm x 15mm9 V

The relevant European standard is IEC 60086-1 Primary batteries - Part 1: General (BS397 in the UK).

The relevant US standard is ANSI C18.1 American National Standard for Dry Cells and Batteries-Specifications.

An extensive series of articles on many aspects of batteries and their use in portable equipment is available at http://www.buchmann.ca/

External Links


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