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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 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".
History
There is some evidence in the form of the Baghdad Battery
from sometime between 250 BC and 250, and possibly
related artifacts in ancient Egypt, of primary cells having been used in ancient times to electroplate, with a precious metal, an object serving as an electrode. Such ancient knowledge in the history of electricity bears no known continuous relationship to the
development of modern batteries. Its form, though, is nearly identical to the principles that are in use today
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 Voltaic pile was a chemical battery developed by Alessandro Volta in 1800. Volta researched the effects which
different metals produced when exposed to salt water. In 1801, Volta demonstrated the
Voltaic cell to Napoleon Bonaparte (who later ennobled him for
his discoveries). 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 early researchers over batteries called the device 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 ft² (83 m²). 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 principle 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 1898 Nathan
Stubblefield received approval for a battery patent (US600457): this electrolytic coil patent is referred to as an "earth battery".
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 developed 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.
Parallel arrangements suffer from the problem that, if one cell discharges faster than its neighbour, current will flow from the
full cell to the empty cell, wasting power and possibly causing overheating. Even worse, if one cell becomes short-circuited due
to an internal fault, its neighbour will be forced to discharge its maximum current into the faulty cell, leading to overheating
and possibly explosion. Cells in parallel are therefore usually fitted with an electronic circuit to protect them against these
problems. In both series and paralllel 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 13.7 V) 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:
| US |
IEC |
ANSI |
Other |
Shape |
Voltage |
| N |
LR1 |
910A |
|
cylinder L 30.2 mm, D 12 mm |
1.5 V |
| AAAA |
|
25A |
MN2500 |
cylinder L 42 mm, D 8 mm |
1.5 V |
| AAA |
LR03 |
24A |
R03,MN2400, AM4,UM4,HP16,micro |
cylinder L 44.5 mm, D 10.5 mm |
1.5 V |
| AA |
LR6 |
15A |
R6,MN1500, AM3,UM3,HP7,mignon |
cylinder L 50 mm, D 14.2 mm |
1.5 V |
| A |
|
|
|
cylinder L 50 mm, D 17 mm |
1.5 V |
| C |
LR14 |
14A |
R14,UM2,MN1400,HP11,baby |
cylinder L 43 mm, D 23 mm |
1.5 V |
| D |
LR20 |
13A |
R20,MN1300,UM1,HP2,mono |
cylinder L 58 mm, D 33 mm |
1.5 V |
| F |
|
|
|
cylinder L 87 mm, D 32 mm |
1.5 V |
| G |
|
|
|
cylinder L 105 mm, D 32 mm |
1.5 V |
| J |
|
|
|
cylinder L 150 mm, D 32 mm |
1.5 V |
| |
|
|
lantern,996 |
rectangular prism 68 mm square × 115 mm |
6 V |
| PP3 |
6L6R1 |
1604A |
6F22,6R61,MN1604 |
rectangular prism 48 mm × 25 mm × 15mm |
9 V |
| PP9 |
6F100 |
1603 |
|
rectangular prism 51.6mm × 65.1 mm × 80.2 mm high |
9 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/
Summary
Disposable
Rechargeable
Battery capacity
The capacity of a battery to store charge is expressed in Ah (ampere hour). If a
battery can provide one ampere (1 A) of current (flow) for one hour, it has a real-world capacity of 1 Ah at
one ampere. If it can provide 1 A for 100 hours, its capacity is 100 Ah (again, at 1 ampere). Likewise,
20 A for 2 hours equals 40 Ah capacity. But...
While a battery that can deliver 10 A for 10 hours can be said to have a capacity of 100 Ah, that is not
how the rating is determined by the manufacturers. A 100 Ah rated battery most likely will not deliver 10 A for 10
hours. Battery manufacturers use a standard method to determine how to rate their batteries. Their rating is based on tests
performed over 20 hours with a discharge rate of 1/20 (5%) of the expected capacity of the battery. So a
100 ampere-hour battery is rated to provide 5 A for 20 hours. The efficiency of a battery is different at
different discharge rates. When discharging at 1/20 of their capacity, batteries are more efficient than at higher discharge
rates.
To calculate the 5% discharge rate of a battery, take the manufacturer's amp-hour rating and divide it by 20. For example, you
have a AA cell rated at 1300 mAh (milliampere hours). The 5% discharge rate from which this rating was derived would be
1300 mAh / 20 hours = 65 mA.
See also
People/inventors
Related electrical topics
Releated electronics concepts
Chemicals used in construction
Related inventions
Other
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