Battery (electricity)
4198
226053404
2008-07-16T16:52:56Z
Ohnoitsjamie
507787
Reverted edits by [[Special:Contributions/Luxuning|Luxuning]] ([[User talk:Luxuning|talk]]) to last version by 162.97.4.57
{{otheruses3|Battery}}
[[Image:Batteries.jpg|thumb|right|300px|Various batteries (clockwise from bottom left): two [[9-volt]], two [[AA battery|AA]], two [[AAA battery|AAA]], one [[D battery|D]], a handheld [[ham radio]] battery, a [[cordless phone]] battery, a [[camcorder]] battery, and one [[C battery|C]].]]
In electronics, a '''battery''' is two or more [[electrochemical cell]]s<ref>Battery" (def. 6), ''The Random House Dictionary of the English Language, the Unabridged Edition (2nd edition)'', 1996 ed.</ref> which store chemical [[energy]] and make it available as electrical energy. Common usage has evolved to include a single electrical cell in the definition.<ref>[http://www.merriam-webster.com/dictionary/battery Merriam-Webster Online Dictionary: "battery"]</ref> There are many types of electrochemical cells, including [[galvanic cell]]s, [[electrolytic cell]]s, [[fuel cell]]s, [[Flow battery|flow cells]] and [[voltaic pile]]s.<ref>{{cite web |url=http://www.pspb.org/e21/media/Compare_pvfc_v108_TN.pdf |title=Spotlight on Photovoltaics & Fuel Cells: A Web-based Study & Comparison |accessdate=2007-03-14 |format=PDF |pages=1-2 }}</ref> A battery's characteristics may vary due to many factors including internal chemistry, [[Electric current|current]] drain and temperature.
One common division of batteries distinguishes two types: [[Primary battery|primary]] (disposable) and [[Secondary battery|secondary]] (rechargeable). Primary batteries are designed to be used once only because they use up their chemicals in an effectively irreversible reaction. Secondary batteries can be recharged because the chemical reactions they use are [[Reversible reaction|reversible]]; they are recharged by running a charging current through the battery, but in an opposite direction to the discharge current.<ref>[http://science.jrank.org/pages/779/Battery.html Battery - Background, Primary cells, Secondary cells - Net Industries Science Encyclopedia]. Retrieved 26 August 2007.</ref> Secondary, also called [[rechargeable batteries]] can be charged and discharged many times before wearing out. After wearing out some batteries can be [[Battery recycling|recycled]].<ref>[http://www.batteryrecycling.com Battery Recycling - Cost-Effective and Safe Disposal - Battery Solutions]. Retrieved 6 January 2008.</ref>
The name "battery" was coined by [[Benjamin Franklin]] for an arrangement of multiple [[Leyden jar]]s (an early type of [[capacitor]]) after a [[Artillery battery|''battery'' of cannon]].
Although an [[Baghdad Battery|early form of electrochemical battery]] may have been used in antiquity, the modern development of batteries started with the [[Voltaic pile]], invented by the Italian physicist [[Alessandro Volta]] in 1800. Since then, batteries have gained popularity as they became portable and useful for many purposes.<ref>[http://www.extremetech.com/article2/0,1697,1155265,00.asp Battery Technology: History - ExtremeTech]. Retrieved 10 September 2007.</ref> The widespread use of batteries has created many [[Electronic waste|environmental concerns]], such as toxic metal pollution.<ref>[http://www.epa.gov/epr/products/batteries.htm Batteries | Product Stewardship | Wastes | EPA]. Retrieved 11 September 2007.</ref> Many reclamation companies [[Battery recycling|recycle batteries]] to reduce the number of batteries going into landfills.<ref name="epagarb">[http://www.epa.gov/garbage/battery.htm Municipal Solid Waste - Commodities: Batteries - EPA]. Retrieved 11 September 2007.</ref>
== History==
The story of the battery begins in the 1780s with the discovery of "animal electricity" by [[Luigi Galvani]], which he published in 1791.<ref> Walter Bernardi, ''The Controversy on Animal Electricity in Eighteenth-Century Italy: Galvani, Volta and Others'', retrieved from http://ppp.unipv.it/Collana/Pages/Libri/Saggi/NuovaVoltiana_PDF/quattro.pdf May 21, 2008</ref> He created an electric circuit consisting of two different metals, with one touching a frog's leg and the other touching both the leg and the first metal, thus closing the circuit. In modern terms, the frog's leg served as both electrolyte and detector, and the metals served as electrodes. He noticed that even though the frog was dead, its legs would twitch when he touched them with the metals.
[[Volta]] realized that the frog's moist tissues could be replaced by cardboard soaked in salt water, and the frog's muscular response could be replaced by another form of electrical detection. He already had studied the electrostatic phenomenon of [[capacitance]], which required measurements of electric charge and of electrical potential. Building on this experience Volta was able to detect electric current through his system, now called a [[voltaic cell]], or cell for short. The terminal voltage of a cell that is not discharging is called its [[electromotive force]] (emf), and has the same unit as electrical potential, named ([[voltage]]) and measured in [[volt]]s, in honor of Volta. In [[1799]], Volta invented the battery by placing many voltaic cells in [[Series and parallel circuits#Series circuits|series]], literally piling them one above the other. This [[Voltaic Pile]] gave a greatly enhanced net emf for the combination,<ref>Willie Weinberg. [http://www.italian-american.com/volta.htm Volta - The Italian American Website of New York]. Accessed 19 March 2007.</ref> with a voltage of about 50 volts for a 32-cell pile.<ref>Saslow, Ch. 8, p. 338.</ref> In many parts of Europe batteries continue to be called piles.
Unfortunately, Volta did not appreciate that the voltage was due to chemical reactions. He thought that his cells were an inexhaustible source of energy, and that the associated chemical effects (e.g. corrosion) were a mere nuisance, rather than, as [[Michael Faraday]] showed around 1830, an unavoidable consequence of their operation.
While early batteries were of great value for experimental purposes, their limitations made them impractical for a large current drain. Later, starting with the [[Daniell cell]] in [[1836]], batteries provided more reliable currents and were adopted by industry for use in stationary devices, particularly in telegraph networks where they were the only practical source of electricity, since electrical distribution networks did not exist then.<ref>[http://www.mpoweruk.com/history.htm#daniell Battery History, Technology, Applications and Development]. Accessed 19 March 2007.</ref> These wet cells used liquid electrolytes, which were prone to leakage and spillage if not handled correctly. Many used glass jars to hold their components, which made them fragile. These characteristics made wet cells unsuitable for portable appliances. Near the end of the 19th century, the invention of [[dry cell|Dry cell batteries]], which replaced liquid electrolyte with a paste, made portable electrical devices practical.
The battery has since become a common power source for many household and industrial applications. According to a [[2005]] estimate, the worldwide battery industry generates [[United States dollar|US$]]48 [[1000000000 (number)|billion]] in sales annually.<ref>[http://www.dfj.com/cgi-bin/artman/publish/article_141.shtml Power Shift: DFJ on the lookout for more power source investments]. Accessed 20 November 2005.</ref>
== How batteries work ==
{{main|Electrochemical cell}}
[[Image:ElectrochemCell.png|thumb|250px|right|A voltaic cell for demonstration purposes. In this example the two half-cells are linked by a salt bridge separator that permits the transfer of ions, but not water molecules.]]
A battery is a device that converts chemical energy directly to electrical energy.<ref>Marshall Brain. [http://electronics.howstuffworks.com/battery.htm "How Batteries Work" - Howstuffworks]. Accessed 28 March 2007.</ref> It consists of one or more voltaic cells. Each voltaic cell consists of two [[half cell]]s connected in series by a conductive electrolyte. One half-cell is the positive electrode and the other is the negative electrode. The electrodes do not touch each other but are electrically connected by the electrolyte, which can be either solid or liquid.<ref>[http://www.open2.net/science/roughscience/library/batteries.htm BBC- Rough Science Library]. Accessed 28 March 2007.</ref> In many cells, the materials are enclosed in a container, and a separator, which is porous to the electrolyte, which prevents the electrodes from coming into contact.
Each half cell has an electromotive force (or emf), determined by its ability to drive electric current from the interior to the exterior of the cell. The net emf of the battery is the difference between the emfs of its half-cells, as first recognized by Volta.<ref>Saslow 338.</ref> Thus, if the electrodes have emfs <math>\mathcal{E}_1</math> and <math>\mathcal{E}_2</math>, then the net emf is <math>\mathcal{E}_{2}-\mathcal{E}_{1}</math>. (Hence, two identical electrodes and a common electrolyte give a zero net emf.)
The electrical potential difference, or <math>\displaystyle{\Delta V_{bat}}</math> across the terminals of a battery is known as ''terminal voltage'' and is measured in [[volt]]s.<ref name="pse943">Knight 943.</ref> The terminal voltage of a battery that is neither charging nor discharging is called the [[open-circuit voltage]] and equals the emf of the battery. Because of internal resistance<ref>Knight 976.</ref>, the terminal voltage of a battery that is discharging is smaller in magnitude than the open-circuit voltage and the terminal voltage of a battery that is charging exceeds the open-circuit voltage.<ref>[http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0030399.html Terminal Voltage - Tiscali Reference]. Originally from ''Hutchinson Encyclopaedia''. Accessed 7 April 2007.</ref> An ideal battery has negligible internal resistance, so it would maintain a constant terminal voltage of <math>\mathcal{E}</math> until exhausted, then dropping to zero. If such a battery maintained 1.5 volts and stored a charge of one [[Coulomb]] than it would perform 1.5 [[Joule]] of work.<ref name=pse943/> In practical batteries the internal resistance will increase as it is discharged, and the open circuit voltage will also decrease as the cell is discharged. If the voltage and resistance are plotted against time the resulting graphs will typically not be a straight line, and the shape of the curve will vary with the chemistry and internal arrangement employed.
The voltage developed across a cell's terminals depends on the chemicals used in it and their respective concentrations. For example, alkaline and carbon-zinc cells both measure approximately 1.5 volts, due to the energy release of the associated chemical reactions.<ref>Dingrando 674.</ref> Because of the high electrochemical potential changes in the reactions of [[lithium]] compounds, lithium cells can provide as much as 3 volts or more.<ref>Dingrando 677.</ref>
== Classification of batteries ==
=== Disposable and rechargeable ===
[[Image:Batterien.jpg|thumb|From top to bottom: Two [[button cell]]s, a 9-volt ''[[PP3 battery]]'', an ''[[AAA battery]]'', an ''[[AA battery]]'', a ''[[C battery]]'', a ''[[D battery]]'', a large ''3R12''.]]
Batteries are usually divided into two broad classes:
* ''Primary'' batteries irreversibly (within limits of practicality) transform chemical energy to electrical energy. When the initial supply of reactants is exhausted, energy cannot be readily restored to the battery by electrical means.<ref name = "wsgiqk">Dingrando 675.</ref>
* ''Secondary'' batteries can be recharged; that is, they can have their chemical reactions reversed by supplying electrical energy to the cell, restoring their original composition.<ref>Fink, Ch. 11, Sec. "Batteries and Fuel Cells."</ref>
Historically, some types of primary batteries used, for example, for [[telegraph]] circuits, were restored to operation by replacing the components of the battery consumed by the chemical reaction. Secondary batteries are not indefinitely rechargeable due to dissipation of the active materials, loss of electrolyte and internal corrosion.
From a user's viewpoint, at least, batteries can be generally divided into two main types: ''non-rechargeable ([[disposable]])'' and ''[[Rechargeable battery|rechargeable]]''. Each type is in wide usage, as each has its own advantages and disadvantages.<ref name="bu50">Isidor Buchmann, [http://batteryuniversity.com/parttwo-50.htm Will secondary batteries replace primaries? - Battery University]. Retrieved 6 January 2008.</ref>
Disposable batteries, also called ''[[primary cell]]s'', are intended to be used once and discarded. These are most commonly used in portable devices with either low current drain, are only used intermittently, or are used well away from an alternative power source. Primary cells were also commonly used for alarm and communication circuits where other electric power was only intermittently available. Primary cells cannot be reliably recharged, since the chemical reactions are not easily reversible and active materials may not return to their original forms. Battery manufacturers recommend against attempting to recharge primary cells, although some electronics enthusiasts claim it is possible to do so using special types of chargers.<ref>[http://www.batteryxtender.com Battery Xtender]. Retrieved 7 March 2007.</ref>
By contrast, rechargeable batteries or ''[[secondary cell]]s'' can be recharged by applying electrical current, which reverses the [[chemical reaction]]s that occur during its use. Devices to supply the appropriate current are called chargers or rechargers.
The oldest form of rechargeable battery still in modern usage is the "[[wet cell]]" [[lead-acid battery]].<ref>Isidor Buchmann, [http://batteryuniversity.com/partone-6.htm Can the lead-acid battery compete in modern times? - Battery University]. Retrieved 2 September 2007.</ref> 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 ensure safe dispersal of the [[hydrogen]] gas produced 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 a large capacity (over approximately 10Ah) is required or where the weight and ease of handling are not concerns.
A common form of lead-acid battery is the modern wet-cell [[car battery]]. This can deliver approximately 10,000 [[watt]]s of power over a short period and has a peak current output that varies from 450 to 1100 [[ampere]]s. An improved type of liquid electrolyte battery is the sealed valve regulated lead acid ([[VRLA]]) battery, popular in the automotive industry as a replacement for the lead-acid wet cell, as well as in many lower capacity roles including smaller vehicles and stationary applications such as [[emergency lighting]] and [[alarm system]]s. The one-way pressure activated valve eliminates electrolyte evaporation while allowing out-gassing to prevent rupture. This greatly improves resistance to damage from vibration and heat. VRLA batteries have the electrolyte immobilized, usually by one of two means:
*''[[Gel battery|Gel batteries]]'' (or "gel cell") contain a semi-solid electrolyte to prevent spillage.
*''[[Absorbed Glass Mat]]'' (AGM) batteries absorb the electrolyte in a special fiberglass matting
Other portable rechargeable batteries include several "dry cell" types, which are sealed units and are therefore useful in appliances such as [[mobile phone]]s and [[Laptop|laptop computers]]. Cells of this type (in order of increasing [[power density]] and cost) include [[Nickel-cadmium battery|nickel-cadmium]] (NiCd), [[Nickel metal hydride battery|nickel metal hydride]] (NiMH) and [[Lithium ion battery|lithium-ion]] (Li-Ion) cells.
Recent developments include batteries with embedded functionality such as [[USBCELL]], with a built-in charger and [[USB]] connector within the AA format, enabling the battery to be charged by plugging into a USB port without a charger,<ref>[http://www.usbcell.com USBCELL - Revolutionary rechargeable USB battery that can charge from any USB port]. Retrieved 6 November 2007.</ref> and [[Low self-discharge NiMH battery|low self-discharge]] (LSD) mix chemistries such as Hybrio,<ref>[http://www.hybriousa.com Long Life Batteries You Can Recharge - Hybrio]. Retrieved 6 January 2008.</ref> ReCyko,<ref>[http://www.gprecyko.com/en/index.html GP ReCyko]. Retrieved 6 January 2008.</ref> and Eneloop,<ref>[http://www.sanyo.co.jp/koho/hypertext4-eng/0511/1101-2e.html SANYO Presents 'eneloop' : A New Battery in place of Dry Cell Battery for the 21st Century]. Retrieved 6 January 2008.</ref> where cells are precharged prior to shipping.
==== Disposable ====
Not designed to be rechargeable - sometimes called "primary cells". "Disposable" may also imply that special disposal procedures must take place for proper disposal according to regulation, depending on battery type.
* [[Zinc-carbon battery]]: mid cost, used in light drain applications.
* [[Zinc-chloride battery]]: similar to zinc-carbon but slightly longer life.
* [[Alkaline battery]]: alkaline/manganese "long life" batteries widely used in both light-drain and heavy-drain applications.
* [[Silver-oxide battery]]: commonly used in hearing aids, watches, and calculators.
* [[Lithium battery|Lithium-Thionyl Chloride battery]]: used in industrial applications, including computers, electric meters and other devices which contain volatile memory circuits and act as a "carryover" voltage to maintain the memory in the event of a main power failure. Other applications include providing power for wireless gas and water meters. The cells are rated at 3.6 Volts and come in 1/2AA, AA, 2/3A, A, C, D & DD sizes. They are relatively expensive, but have a long shelf life, losing less than 10% of their capacity in ten years.<ref>[http://www.tadiranbat.com/betterbydesign.php Tadiran Batteries - Better By Design]. Retrieved 21 January 2008.</ref>
* [[Mercury battery]]: formerly used in digital watches, radio communications, and portable electronic instruments. Manufactured only for specialist applications due to [[toxicity]].
* [[Zinc-air battery]]: commonly used in [[hearing aid]]s.
* [[Thermal Battery|Thermal battery]]: high-temperature reserve. Almost exclusively military applications.
* [[Water-activated battery]]: used for [[radiosondes]] and emergency applications.
* [[Nickel Oxyhydroxide battery]]: Ideal for applications that use bursts of high current, such as digital cameras. They will last two times longer than alkaline batteries in digital cameras.<ref>Edward C. Baig, [http://www.usatoday.com/tech/columnist/edwardbaig/2006-02-01-battery-test_x.htm USATODAY.com - Batteries up! With more power]. Retrieved 21 January 2008.</ref>
* [[Paper battery]]: In August 2007, a research team at [[Rensselaer Polytechnic Institute|RPI]] (led by Drs. [[Robert Linhardt]], [[Pulickel M. Ajayan]], and [[Omkaram Nalamasu]]) developed a paper battery with aligned carbon nanotubes, designed to function as both a lithium-ion battery and a [[supercapacitor]], using [[ionic liquid]], essentially a liquid [[salt]], as [[electrolyte]]. The sheets can be rolled, twisted, folded, or cut into numerous shapes with no loss of integrity or efficiency, or stacked, like printer paper (or a [[voltaic pile]]), to boost total output. As well, they can be made in a variety of sizes, from [[postage stamp]] to [[broadsheet]]. Their light weight and low cost make them attractive for portable electronics, [[aircraft]], and [[automobile]]s, while their ability to use electrolytes in blood make them potentially useful for medical devices such as [[pacemakers]]. In addition, they are [[biodegradable]], unlike most other disposable cells.<ref>[http://theglobeandmail.com/servlet/story/LAC.20070814.PAPER14/TPStory/?query=paper+battery/|14 August 2007 ''Globe and Mail'']</ref><ref>Michael Mullaney, [http://news.rpi.edu/update.do?artcenterkey=2280 RPI: News & Events - Beyond Batteries: Storing Power in a Sheet of Paper]. Retrieved 14 August 2007.</ref>
==== Rechargeable ====
[[Image:Nokia Battery Hologram.jpg|thumb|A rechargeable lithium polymer [[Nokia]] [[mobile phone]] battery.]]
:{{main|Rechargeable battery|Battery charger}}
Also known as secondary batteries or accumulators. The [[National Electrical Manufacturers Association]] has estimated that U.S. demand for rechargeables is growing twice as fast as demand for non-rechargeables. <ref>[http://epa.gov/epaoswer/non-hw/reduce/epr/products/batteries.htm Batteries | Product Stewardship | Wastes | EPA<!-- Bot generated title -->]</ref> There are a few main types:
*[[Nickel-cadmium battery]] (NiCd): Best used for motorized equipment and other high-discharge, short-term devices. NiCd batteries can withstand even more drain than NiMH; however, the mAh rating is not high enough to keep a device running for very long, and the [[memory effect]] is far more severe.<ref>[http://mpoweruk.com/nicad.htm MPower: Nickel Cadmium NiCad Batteries]. Retrieved 2006 August 2007.</ref>
*[[Nickel-metal hydride battery]] (NiMH): Best used for high-tech devices. NiMH batteries can last up to four times longer than alkaline batteries because NiMH can withstand high current for a long while.<ref>[http://energizer.com/products/rechargeables Energizer.com - Products - Rechargeables]. Retrieved 26 August 2007.</ref>
* [[Lithium ion battery]]: commonly used in digital cameras. Sometimes used in watches and computer clocks. Very long life (up to ten years in wristwatches) and capable of delivering high currents but expensive. Will operate in sub-zero temperatures.
* [[Lithium ion polymer battery]] (Li poly battery): Polymer Li-ion batteries have been applied to [[PDA]]s, [[Notebook computer]]s, [[Bluetooth]] devices, military uses and others. The main anode material of lithium-ion polymer batteries is lithium cobalt dioxide.
<ref>[http://www.eemb.com/productcenter/Industry/LP/LP.html EEMB Battery -lithium polymer battery]</ref>
*[[Rechargeable alkaline battery]]: Uses similar chemistry as non-rechargeable alkaline batteries and are best suited for similar applications. <ref>[http://www.juicebattery.com/index.cfm/MenuItemID/105/MenuGroup/Home.htm] Retrieved 21 January 2008.</ref> Additionally, they hold their charge for years, unlike NiCd and NiMH batteries. However drain/charging pattern can greatly affect their efficacy and lifespan.
*LiFeP as used in the OLPC laptop.
*[[Lead-acid battery]], as mentioned above.
===== Flow batteries =====
[[Flow Battery|Flow batteries]] are a special class of rechargeable battery where additional quantities of [[electrolyte]] are stored outside the main power cell of the battery, and circulated through it by pumps or by movement.<ref name="mpowerf">[http://www.mpoweruk.com/flow.htm Flow Batteries - MPower]. Retrieved 9 September 2007.</ref> Flow batteries can have extremely large capacities and are used in marine applications and are gaining popularity in [[grid energy storage]] applications.
[[Zinc-bromine flow battery|Zinc-bromine]]<ref name=mpowerf/> and [[Vanadium redox battery|vanadium redox batteries]] are typical examples of commercially available flow batteries.
=== Homemade cells ===
Almost any liquid or moist object that has enough ions to be electrically conductive can serve as the electrolyte for a cell. As a novelty or science demonstration, it is possible to insert two electrodes made of different metals into a [[lemon battery|lemon]],<ref>[http://ushistory.org/franklin/fun/lemon.htm ushistory.org: The Lemon Battery]. Accessed 10 April 2007.</ref> [[potato]],<ref>[http://pbskids.org/zoom/activities/phenom/potatobattery.html ZOOM . activities . phenom . Potato Battery]. Accessed 10 April 2007.</ref> et cetera and generate small amounts of electricity. "Two-potato clocks" are also widely available in hobby and toy stores; they consist of a pair of cells, each consisting of a potato (lemon, et cetera) with two electrodes inserted into it, wired in series to form a battery with enough voltage to power a digital clock.<ref>[http://www.sciencekit.com/category.asp_Q_c_E_756000&cr=1220 Two-Potato Clock - Science Kit and Boreal Laboratories]. Accessed 10 April 2007.</ref> Homemade cells of this kind are of no real practical use, because they produce far less current—and cost far more per unit of energy generated—than commercial cells, due to the need for frequent replacement of the fruit or vegetable. In addition, one can make a [[voltaic pile]] from two coins (such as a [[nickel]] and a [[penny]]) and a piece of [[paper towel]] dipped in [[saline water|salt water]]. Such a pile would make very little voltage itself, but when many of them are stacked together in [[series circuit|series]], they can replace normal batteries for a short amount of time.<ref>[http://electronics.howstuffworks.com/battery1.htm Howstuffworks "Battery Experiments: Voltaic Pile"]. Accessed 10 April 2007.</ref>
Sony has developed a biologically friendly battery that generates electricity from sugar in a way that is similar to the processes observed in living organisms. The battery generates electricity through the use of enzymes that break down carbohydrates, which are essentially sugar.<ref>[http://informationweek.com/news/showArticle.jhtml?articleID=201802311 Sony Develops A Bio Battery Powered By Sugar]. Accessed 24 August 2007.</ref>
Lead acid cells can easily be manufactured at home, but a tedious charge/discharge cycle is needed to 'form' the plates. This is a process whereby lead sulfate forms on the plates, and during charge is converted to lead dioxide (positive plate) and pure lead (negative plate). Repeating this process results in a microscopically rough surface, with far greater surface area being exposed. This increases the current the cell can deliver. For an example, see [http://windpower.org.za/batteries/batteries.html].
[[Daniell cell]]s are also easy to make at home. [[Aluminium battery|Aluminum-air batteries]] can also be produced with high purity aluminum. [[Aluminum foil]] batteries will produce some electricity, but they are not very efficient, in part because a significant amount of [[hydrogen]] gas is produced.
=== Battery packs ===
{{main|Battery pack}}
The cells in a battery can be connected in parallel, series or in both. A parallel combination of cells has the same [[voltage]] as a single cell, but can supply a higher [[Current (electricity)|current]] (the sum of the currents from all the cells). 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 batteries and 12-volt [[automobile]] batteries, have several cells connected in series inside the casing.<ref>[http://electronics.howstuffworks.com/battery3.htm Howstuffworks "Battery Reactions and Chemistry"]. Retrieved 20 September 2007.</ref> 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.<ref>Isidor Buchmann, [http://www.batteryuniversity.com/partone-24.htm Serial and parallel battery configurations - Battery University]. Retrieved 26 August 2007.</ref> Cells in parallel are therefore usually fitted with an electronic circuit to protect them against these problems. In both series and parallel types, the energy stored in the battery is equal to the sum of the energies stored in all the cells.
=== Traction battery ===
<!-- [[traction battery]] links here -->
[[Image:BrailleAGMCarbonBatteryCutawayHR.jpg|thumb|300px|right|AGM Battery Cutaway Drawing of Braille Carbon Battery. Click to Enlarge Detail]]
A traction battery is a high-power battery designed to provide propulsion to move a vehicle, such as an [[electric car]] or tow motor. A major design consideration is [[power to weight ratio]] since the vehicle must carry the battery.<ref>[http://engineersedge.com/battery/traction_battery.htm Engineers Edge: Traction Battery]. Retrieved 26 August 2007.</ref> While conventional [[lead acid]] batteries<ref>[http://batterycouncil.org/batteries.html Battery Council International: Lead Acid Batteries]. Retrieved 26 August 2007.</ref> with liquid [[electrolyte]] have been used, gelled electrolyte<ref>http://mastervolt-solar.com/batteries/index.asp Products: Mastervolt gel batteries]. Retrieved 26 August 2007.</ref> and [[Absorbed Glass Mat|AGM-type]]<ref>[http://johnsoncontrols.com/publish/us/en/products/power_solutions/Battery_Technology_Centers/AGM/agm_technology_for.html Johnson Controls Inc.: AGM technology for semi-traction]. Retrieved 26 August 2007.</ref> can also be used, especially in smaller sizes.
The largest installations of batteries for propulsion of vehicles are found in [[submarine]]s, although the toxic gas produced by seawater contact with acid electrolyte is a considerable hazard.
Battery types commercially used in electric vehicles include
* [[lead-acid battery]], which uses [[lead(IV) oxide]] (PbO<sub>2</sub>) and [[sulfuric acid]] (H<sub>2</sub>SO<sub>4</sub>)<ref name = "wsgiqk"/>
** flooded type with liquid electrolyte
** gel
** [[Absorbed Glass Mat|AGM-type (Absorbed Glass Mat)]]
* [[Nickel-metal hydride battery|Nickel-metal hydride]] and [[Nickel-Cadmium battery|Nickel-Cadmium]] batteries
* [[Lithium-Ion battery|Lithium-Ion]] and [[Lithium polymer battery|Lithium-Polymer]] batteries
* [[Molten salt battery|Zebra Na/NiCl<sub>2</sub>]] battery operating at 270 °C requiring cooling in case of temperature excursions
* [[NiZn battery]] (higher cell voltage 1.6 V and thus 25% increased specific energy, very short lifespan)
See also: [[battery electric vehicles]] and [[hydrogen vehicle]].
== Battery capacity and discharging ==
[[Image:Battery checker.jpg|thumb|250px|A device to check the charge of batteries]]
The more electrolyte and electrode material there is in the cell, the greater the capacity of the cell. Thus a small cell has less capacity than a larger cell, given the same chemistry (e.g. [[alkaline cell]]s), though they develop the same open-circuit voltage.<ref name=aappc/>
Because of the chemical reactions within the cells, the capacity of a battery depends on the discharge conditions such as the magnitude of the current, the duration of the current, the allowable terminal voltage of the battery, temperature and other factors.<ref name="aappc">[http://www.aaportablepower.com/BatteryKnowledge/BatteryKnowledge.asp Battery Knowledge - AA Portable Power Corp.]. Accessed 16 April 2007.</ref>
The available capacity of a battery depends upon the rate at which it is discharged.<ref name="techlib">[http://www.techlib.com/reference/batteries.html Battery Capacity - Techlib]. Accessed 10 April 2007.</ref> If a battery is discharged at a relatively high rate, the available capacity will be lower than expected.
The battery capacity that battery manufacturers print on a battery is the product of 20 hours multiplied by the maximum constant current that a new battery can supply for 20 hours at 68 F° (20 C°),<ref>[http://xtronics.com/reference/batterap.htm Battery Backup Application Handbook - Transtronics]. Retrieved 5 January 2008.</ref> down to a predetermined terminal voltage per cell.
A battery rated at 100 A·h will deliver 5 A over a 20 hour period at [[room temperature]]. However, if it is instead discharged at 50 A, it will run out of charge before the theoretically-expected 2 hours.
For this reason, a battery capacity rating is always related to an expected discharge duration—the standard duration is 20 hours.
:<math>t = \frac Q I</math>
where
:<math>Q</math> is the battery capacity (typically given in [[mAh|mA·h]]).
:<math>I</math> is the current drawn from battery ([[wiktionary:mA|mA]]).
:<math>t</math> is the amount of time (in hours) that a battery can sustain.
The relationship between current, discharge time, and capacity for a lead acid battery is expressed by [[Peukert's law]]. The [[efficiency]] of a battery is different at different discharge rates. When discharging at low rate, the battery's energy is delivered more efficiently than at higher discharge rates.
In general, the higher the ampere-hour rating, the longer the battery will last for a certain load. Installing batteries with different A·h ratings will not affect the operation of a device rated for a specific voltage unless the load limits of the battery are exceeded. Theoretically, a battery would operate at its A·h rating, but realistically, high-drain loads like [[digital camera]]s can result in lower actual energy, most notably for alkaline batteries.<ref name=bu50/> For example, a battery rated at 2000 mA·h may not sustain a current of 1 A for the full two hours.
==Space Applications==
The [[National Aeronautics and Space Administration]] (NASA) recognized the crucial importance of batteries very early in the space program.<ref>[http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19640015888_1964015888.pdf Francis, Howard T., Space Battery Handbook, Armour Research Foundation, Illinois Institute of Technology, April 15, 1963]</ref> has funded many programs to develop batteries for use in spacecraft. Such batteries must be sturdy, resistant to conditions of cold and heat, and able to withstand the [[sterilization (microbiology)]] procedures required for all equipment aboard a spacecraft. The [[Jet Propulsion Laboratory]], in [[Pasadena]], [[California]]. is one of NASA's main recipients of research and development funding. NASA's battery work has included studies on [[Nickel-Cadmium battery|nickel-cadmium (Ni-Cad)]], nickel-hydrogen (NiH), [[Nickel-metal hydride battery|nickel-metal-hydride (NiMH)]] and [[Lithium battery|lithium batteries]], among others.<ref>http://www.nap.edu/openbook.php?record_id=2351&page=38 Technology for Small Spacecraft, National Academies Press, 1994, pp.37-38]</ref> An important contributor to JPL's work, and to improving battery science and technology, was George F. Nordblom, Ph.D. ([[1914]]-[[2008]]), a senior research chemist at the Electric Storage Battery Company in [[Yardley, Pennsylvania]] who held nine [[patent]]s for improving [[electroplating]] and battery function.<ref>http://www.philly.com/philly/obituaries/20080620_George_F__Nordblom__94__chemist.html George F. Nordblom, 94, Chemist, Philadelphia Inquirer, June 20, 2008]</ref>
{| class="wikitable sortable"
|+Typical alkaline [[List of battery sizes|battery sizes]] and capacities<ref>{{cite web
| url= http://data.energizer.com/QuickSearch_Action.aspx?group=1&name=Energizer%20Alkaline
| title= Alkaline Technical Information
| publisher= [[Energizer]] }}</ref> (at lowest discharge rates, to 0.8V/cell)
! Diagram !! Size !! Capacity [[Ampere-hour|(mA·h)]] !! Voltage !! [[American National Standards Institute|ANSI]]/[[National Electronic Distributors Association|NEDA]] !! [[International Electrotechnical Commission|IEC]] !! Diam. (mm) !! Mass (g) !! Height (mm) !! Length (mm) !! Width (mm)
|-
| || [[AAAA battery|AAAA]] || 625 || 1.5 || 25A || LR8D425 || 8.3 || 6.5 || 42.5 || cylindrical || cylindrical
|-
| [[Image:N battery size.svg]] || N || 1000 || 1.5 || 910A || LR1 || 12 || 9 || 30.2 || cylindrical || cylindrical
|-
| [[Image:AAA battery size.svg]] || [[AAA battery|AAA]] || 1250 || 1.5 || 24A || LR03 || 10.5 || 11.5 || 44.5 || cylindrical || cylindrical
|-
| [[Image:AA battery size.svg]] || [[aa battery|AA]] || 2850 || 1.5 || 15A || LR6 || 14.5 || 23 || 50.5 || cylindrical || cylindrical
|-
| || J || 625 || 6 || 1412A || 4LR61 || prismatic || 30 || 48.5 || 35.6 || 9.18
|-
| || [[9V battery|9V]] || 625 || 9 || 1604A || 6LR61 || prismatic || 45.6 || 48.5 || 26.5 || 17.5
|-
| [[Image:C battery size.svg]] || [[c battery|C]] || 8350 || 1.5 || 14A || LR14 || 26.2 || 66.2 || 50 || cylindrical || cylindrical
|-
| [[Image:D battery size.svg]] || [[d battery|D]] || 20500 || 1.5 || 13A || LR20 || 34.2 || 148 || 61.5 || cylindrical || cylindrical
|-
| || Lantern || 26000 || 6 || 915A || 4R25Y || prismatic || 885 || 112 || 68.2 || 68.2
|-
| || Lantern || 26000 || 6 || 908A || 4LR25X || prismatic || 885 || 115 || 68.2 || 68.2
|-
| || Lantern || 52000 || 6 || 918A || 4LR25-2 || prismatic || 1900 || 127 || 136.5 || 73
|}
Discharging performance of all batteries drops at low temperature.<ref>[http://www.batteryuniversity.com/partone-15.htm Discharging at high and low temperature]</ref>
== Battery lifetime ==
=== Life of primary batteries ===
Even if never taken out of the original package, disposable (or "primary") batteries can lose 8 to 20 percent of their original charge every year at a temperature of about 20°–30°C.<ref>[http://www.corrosion-doctors.org/Batteries/self-compare.htm Self discharge of batteries - Corrosion Doctors]. Retrieved 9 September 2007.</ref> This is known as the "self discharge" rate and is due to non-current-producing "side" chemical reactions, which occur within the cell even if no load is applied to it. The rate of the side reactions is reduced if the batteries are stored at low temperature, although some batteries can be damaged by freezing. High or low temperatures may reduce battery performance. This will affect the initial voltage of the battery. For an AA alkaline battery this initial voltage is approximately normally distributed around 1.6 volts.
=== Life of rechargeable batteries ===
Rechargeable batteries traditionally self-discharge more rapidly than disposable alkaline batteries; up to three percent a day (depending on temperature). However, modern Lithium designs have reduced the self-discharge rate to a relatively low level (but still poorer than for primary batteries). Due to their poor shelf life, rechargeable batteries should not be stored and then relied upon to power flashlights or radios in an emergency. For this reason, it is a good idea to keep alkaline batteries on hand. NiCd Batteries are almost always "dead" when purchased, and must be charged before first use.
Although rechargeable batteries may be refreshed by charging, they still suffer degradation through usage. Low-capacity Nickel Metal Hydride (NiMH) batteries (1700-2000 mA·h) can be charged for about 1000 cycles, whereas high capacity NiMH batteries (above 2500 mA·h) can be charged for about 500 cycles.<ref name="tomdistr">[http://www.nimhbattery.com/batteries-rechargeable-tips-win.htm Rechargeable battery Tips - NIMH Technology Information]. Retrieved 10 August 2007.</ref> Nickel Cadmium (NiCd) batteries tend to be rated for 1,000 cycles before their internal resistance increases beyond usable values. Normally a fast charge, rather than a slow overnight charge, will result in a shorter battery lifespan.<ref name=tomdistr/> However, if the overnight charger is not "smart" (i.e. it cannot detect when the battery is fully charged), then overcharging is likely, which will damage the battery.<ref>[http://www.greenbatteries.com/batterymyths.html#Quick battery myths vs battery facts - free information to help you learn the difference]. Retrieved 10 August 2007.</ref> Degradation usually occurs because electrolyte migrates away from the electrodes or because active material falls off the electrodes. NiCd batteries suffer the drawback that they should be fully discharged before recharge. Without full discharge, crystals may build up on the electrodes, thus decreasing the active surface area and increasing internal resistance. This decreases battery capacity and causes the dreaded "[[memory effect]]". These electrode crystals can also penetrate the electrolyte separator, thereby causing shorts. NiMH, although similar in chemistry, does not suffer from "[[memory effect]]" to quite this extent.<ref>[http://rechargeablebatteryinfo.com/rechargeable-batteries-memory-effect.php What does ‘memory effect’ mean?]. Retrieved 10 August 2007.</ref>
Automotive lead-acid rechargeable batteries have a much harder life. Because of vibration, shock, heat, cold, and sulfation of their lead plates, few automotive batteries last beyond six years of regular use. Automotive starting batteries have many thin plates to provide as much current as possible in a reasonably small package. Typically they are only drained a small amount before recharge. Care should be taken to avoid deep discharging a starting battery, since each [[charge and discharge cycle]] causes active material to be shed from the plates. Hole formation in the plates leads to less surface area for the current-producing chemical reactions, resulting in less available current when under load. Leaving a lead-acid battery in a deeply discharged state for any significant length of time allows the lead sulfate to crystallize, making it difficult or impossible to remove during the charging process. This can result in a permanent reduction in the available plate surface, and therefore reduced current output and energy capacity.
"Deep-Cycle" lead-acid batteries such as those used in electric golf carts have much thicker plates to aid their longevity. The main benefit of the lead-acid battery is its low cost; the main drawbacks are its large size and weight for a given capacity and voltage. Lead-acid batteries should never be discharged to below 20% of their full capacity, because internal resistance will cause heat and damage when they are recharged. Deep-cycle lead-acid systems often use a low-charge warning light or a low-charge power cut-off switch to prevent the type of damage that will shorten the battery's life.
Special "reserve" batteries intended for long storage in emergency equipment or munitions keep the electrolyte of the battery separate from the plates until the battery is activated, allowing the cells to be filled with the electrolyte. Shelf times for such batteries can be years or decades. However, their construction is more expensive than more common forms.
=== Extending battery life ===
Battery life can be extended by storing the batteries at a low temperature, as in a [[refrigerator]] or [[freezer]], because the chemical reactions in the batteries are slower. Such storage can extend the life of alkaline batteries by ~5%; while the charge of rechargeable batteries can be extended from a few days up to several months.<ref>[http://ask.yahoo.com/ask/20011219.html Ask Yahoo: Does putting batteries in the freezer make them last longer?]. Retrieved 7 March 2007.</ref> In order to reach their maximum voltage, batteries must be returned to room temperature; therefore, alkaline battery manufacturers like [[Duracell]] do not recommend refrigerating or freezing batteries.<ref>[http://www.duracell.com/care_disposal/care.asp Duracell: Battery Care]. Retrieved 7 March 2007.</ref>
==Battery hazards==
A battery explosion is caused by the misuse or malfunction of a battery, such as attempting to recharge a primary (non-rechargeable) battery,<ref>[http://www.energizer.com/learning-center/battery-care/Pages/dos-and-donts.aspx Energizer.com - Learning Center - Energizer and the Environment]. Accessed 17 December 2007.</ref> or [[short circuit]]ing a battery.<ref name="globat">[http://faq.global-batteries.com/idx.php/7/3/article Battery dont's - Global-Batteries]. Retrieved 20 August 2007.</ref> With car batteries, explosions are most likely to occur when a short circuit generates very large currents. In addition, car batteries liberate [[hydrogen]] when they are overcharged (because of [[electrolysis]] of the water in the electrolyte). Normally the amount of overcharging is very small, as is the amount of explosive gas developed, and the gas dissipates quickly. However, when "jumping" a car battery, the high current can cause the rapid release of large volumes of hydrogen, which can be ignited by a nearby spark (for example, when removing the jumper cables).
When a battery is recharged at an excessive rate, an explosive gas mixture of hydrogen and oxygen may be produced faster than it can escape from within the walls of the battery, leading to pressure build-up and the possibility of the battery case bursting. In extreme cases, the battery acid may spray violently from the casing of the battery and cause injury. Overcharging—that is, attempting to charge a battery beyond its electrical capacity—can also lead to a battery explosion, leakage, or irreversible damage to the battery. It may also cause damage to the charger or device in which the overcharged battery is later used. Additionally, disposing of a battery in fire may cause an explosion as steam builds up within the sealed case of the battery.<ref name=globat/>
== Environmental concerns ==
Battery manufacture consumes resources and often involves hazardous chemicals. Used batteries also contribute to [[electronic waste]]. Some areas now have battery [[recycling]] services available to recover some of the materials from used batteries.<ref>[http://earth911.org/recycling/battery-recycling Battery Recycling » Earth 911]. Retrieved 9 September 2007.</ref> Batteries may be harmful or fatal if [[swallowing|swallow]]ed.<ref>[http://data.energizer.com/PDFs/carbonzinc_psds.pdf Product Safety DataSheet - Energizer] (PDF, p. 2). Retrieved 9 September 2007.</ref> Recycling or proper disposal prevents dangerous elements (such as [[lead]], [[mercury (element)|mercury]], and [[cadmium]]) found in some types of batteries from entering the environment. In the United States, Americans purchase nearly three billion batteries annually, and about 179,000 tons of those end up in landfills across the country.<ref name = "zbwcax">[http://www.drunkanswers.com/batteries.html] (p. 1). Retrieved 13 May 2008.</ref> In the United States the [[Environmental Protection Agency]]’s Mercury-Containing and Rechargeable Battery Management Act of 1996, has reduced the amount of mercury in regular household batteries. Recycling programs for lead and cadmium batteries have been put in place.<ref name = "zbwcax"/> Recycling and disposal regulations may in the future apply to alkaline and nickel-metal hydride batteries.
== See also ==
{{EnergyPortal}}
{{portalpar|Electronics|Nuvola_apps_ksim.png}}
{|
|- valign=top
| width=250 align=left |
* [[A battery (vacuum tubes)]]
* [[B battery (vacuum tubes)]]
* [[C battery (vacuum tubes)]]
* [[AA battery]]
* [[AAA battery]]
* [[AAAA battery]]
* [[C battery]]
* [[D battery]]
* [[Alkaline battery]]
* [[Battery Directive]]
* [[Battery holder]]
* [[Battery isolator]]
* [[Battery recycling]]
* [[Battery terminals]]
| width=250 align=left |
* [[Car battery]]
* [[Galvanic cell]]
* [[Electrochemical cell]]
* [[Energy density]]
* [[Lead-acid battery]]
* [[List of battery sizes]]
* [[List of battery types]]
* Nano [[titanate]]
* [[Nanowire battery]]
* [[Recharging batteries]]
* [[Replacing batteries]]
* [[Thermal runaway]]
* [[Trickle charging]]
* [[Watch battery]]
|}
== References ==
{{reflist}}
== Further reading ==
*{{cite book|last=Dingrando|first=Laurel|coauthors=et al.|title=Chemistry: Matter and Change|year=2007|publisher=Glencoe/McGraw-Hill|location=New York|isbn=978-0-07-877237-5}} Ch. 21 (pp. 662-695) is on electrochemistry.
*{{cite book|last=Fink|first=Donald G.|coauthors=H. Wayne Beaty|title=Standard Handbook for Electrical Engineers, Eleventh Edition|year=1978|publisher=McGraw-Hill|location=New York|isbn=0-07020974-X}}
*{{cite book|last=Knight|first=Randall D.|title=Physics for Scientists and Engineers: A Strategic Approach|year=2004|publisher=Pearson Education|location=San Francisco|isbn=0-8053-8960-1}} Chs. 28-31 (pp. 879-995) contain information on electric potential.
*{{cite book|last=Linden|first=David|coauthors=Thomas B. Reddy|title=Handbook Of Batteries|year=2001|publisher=McGraw-Hill|location=New York|isbn=0-0713-5978-8}}
*{{cite book|last=Saslow|first=Wayne M.|title=Electricity, Magnetism, and Light|year=2002|publisher=Thomson Learning|location=Toronto|isbn=0-12-619455-6}} Chs. 8-9 (pp. 336-418) have more information on batteries.
== External links ==
{{commons|Battery}}
* [http://batteryuniversity.com/index.htm Battery University]
* [http://electronics.howstuffworks.com/battery.htm HowStuffWorks: How batteries work]
* [http://www.batteriesplus.com/t-battery-recycling-process.aspx Batteries Recycling Process]
* [http://mobilitynow.org/2007/05/10/battery-life-15-minutes/ Cellphone batteries explained]
* [http://www.digitalcamera-hq.com/digital-cameras/batteries_guide.html Battery guide for digital cameras]
* [http://www.batteries-online.co.uk/ Battery and batteries knowledge base]
* [http://www.medi-stim.com/battery/boverview.htm Battery Overview]
* [http://www.eurekalert.org/pub_releases/2007-08/rpi-bbs080907.php Storing power in a sheet of paper]
* [http://www.mpoweruk.com/ Comprehensive knowledge base about battery technology, battery applications, chargers and ancillary equipment].
* [http://www.understandingnano.com/batteries.html Improvements in battery performance due to nanotechnology]
* [http://electrochem.cwru.edu/ed/encycl/art-b02-batt-nonr.htm Nonrechargeable batteries]
* [http://www.laptopbatteryinc.com Best Laptop Battery]
* [http://www.drunkanswers.com/batteries.html What Are The Effects Of Household Batteries On The Environment?]
* [http://support.radioshack.com/support_tutorials/batteries/batgd-c01.htm Battery comparison from Radio Shack]
* [http://208.106.141.230/admin/FILES/ANSI%20Battery%20Standardization%20History.pdf A Brief History of the Standardization of Portable Cells and Batteries in the United States]
[[Category:Electric batteries|*]]
[[Category:Recyclable materials]]
[[ar:بطارية كهربائية]]
[[az:Batareya]]
[[bg:Батерия]]
[[ca:Bateria elèctrica]]
[[da:Batteri (elektricitet)]]
[[de:Batterie]]
[[el:Μπαταρία]]
[[es:Pila eléctrica]]
[[eo:Baterio]]
[[fr:Pile électrique]]
[[ko:전지]]
[[hr:Baterija]]
[[is:Rafhlaða]]
[[it:Batteria (chimica)]]
[[he:סוללה חשמלית]]
[[ku:Baterî]]
[[nl:Batterij (elektrisch)]]
[[ja:電池]]
[[no:Elektrisk batteri]]
[[nn:Elektrisk batteri]]
[[pl:Bateria ogniw]]
[[pt:Pilha]]
[[ru:Батарея (электротехника)]]
[[simple:Battery]]
[[sr:Батерија]]
[[fi:Paristo]]
[[sv:Batteri (elektricitet)]]
[[th:แบตเตอรี่]]
[[ur:Car battery]]
[[zh-yue:電池]]
[[zh:电池]]