Examine individual changes

'[[Image:Nickel-hydrogen battery.jpg|thumb|right]] A '''nickel–hydrogen battery''' (NiH₂ or Ni–H₂) is a rechargeable electrochemical power source based on [[nickel]] and [[hydrogen]].<ref>[http://www.che.sc.edu/faculty/weidner/Publications/Weidner_JPS_141_326.pdf A simplified physics-based model for nickel hydrogen battery]</ref> It differs from a [[Nickel–metal hydride battery|nickel–metal hydride (NIMH) battery]] by the use of [[hydrogen]] in gaseous form, stored in a pressurized [[Electrochemical cell|cell]] at up to 1200&nbsp;[[Pounds per square inch|psi]] (82.7&nbsp;[[Bar (unit)|bar]]) pressure.<ref>[http://www.nasa.gov/offices/oce/llis/0704.html Nickel-hydrogen spacecraft battery handling and storage practice]</ref> NiH₂ cells using 26% [[potassium hydroxide]] (KOH) as an [[electrolyte]] have shown a [[service life]] of 15 years or more at 80% [[depth of discharge]] (DOD)<ref>[http://pdf.aiaa.org/jaPreview/JPP/1996/PVJAPRE24119.pdf Potassium hydroxide electrolyte for long-term mickel-hydrogen geosynchronous missions]</ref> The [[energy density]] is 75 [[Watt hour|Wh]]/[[kg]], 60 Wh/dm³<ref>[http://ocw.mit.edu/courses/aeronautics-and-astronautics/16-851-satellite-engineering-fall-2003/lecture-notes/l3_scpowersys_dm_done2.pdf Spacecraft Power Systems Pag.9]</ref> [[Power-to-weight ratio|specific power]] 220 W/kg.<ref>[http://gltrs.grc.nasa.gov/reports/2001/CR-2001-210563-PART2.pdf NASA/CR—2001-210563/PART2 -Pag.10]</ref> The [[open-circuit voltage]] is 1.55 [[Volt|V]], the average voltage during discharge is 1.25 V.<ref>[http://theses.gla.ac.uk/373/01/2008AsifPhD.pdf Optimization of spacecraft electrical power subsystems -Pag.40]</ref> While the energy density is only around one third as that of a [[lithium battery]], the specific property of the nickel–hydrogen battery is its long life: the cells handle more than 20,000 charge cycles<ref>[http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel3/62/3208/00103781.pdf?arnumber=103781 Five-year update: nickel hydrogen industry survey]</ref> with 85% energy efficiency and 100% faradaic efficiency. NiH₂ [[Rechargeable battery|rechargeable batteries]] possess good electrical properties which make them attractive for the [[energy storage]] of electrical energy in satellites<ref>[http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940023606_1994023606.pdf Ni-H₂ Cell Characterization for INTELSAT Programs]</ref> and [[space probe]]s. For example, the [[ISS]],<ref>[http://gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?2002/TM-2002-211803.html Validation of International Space Station electrical performance model via on-orbit telemetry]</ref> [[Mercury Messenger]],<ref>http://www.nasa.gov/pdf/168019main_MESSENGER_71504_PressKit.pdf</ref> [[2001 Mars Odyssey|Mars Odyssey]]<ref>[http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/8043/22223/01035418.pdf?arnumber=1035418 A lightweight high reliability single battery power system for interplanetary spacecraft]</ref> and the [[Mars Global Surveyor]]<ref>[http://www.astronautix.com/craft/marveyor.htm Mars Global Surveyor]</ref> are equipped with nickel–hydrogen batteries. The [[Hubble Space Telescope]], when its original batteries were changed in May 2009 more than 19 years after launch, led with the highest number of [[Charge cycle|charge and discharge cycles]] of any NiH₂ battery in [[low earth orbit]].<ref>[http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/9582/30300/01392024.pdf?arnumber=1392024 NiH₂ reliability impact upon Hubble Space Telescope battery replacement]</ref> ==History== The development of the nickel hydrogen battery started in 1970 at [[COMSAT|Comsat]]<ref>[http://pdf.aiaa.org/jaPreview/JE/1982/PVJAPRE62569.pdf Nickel-hydrogen battery technology—development and status]</ref> and was used for the first time in 1977 aboard the U.S. Navy's [[Navigation technology satellite-2]] (NTS-2).<ref>[http://www.aiaa.org/content.cfm?pageid=406&gTable=japaperimportPre97&gID=57704 NTS-2 Nickel-Hydrogen Battery Performance 31]</ref> Currently, the major manufactures of nickel-hydrogen batteries are Eagle-Pitcher Technologies and Johnson Controls, Inc. ==Characteristics== The nickel-hydrogen battery combines the positive nickel electrode of a nickel-cadmium battery, and the negative electrode includes the catalyst and gas diffusion elements of a [[fuel cell]]. During discharge, hydrogen contained in the pressure vessel is oxidized into water while the nickel oxyhydroxide electrode is reduced to nickel hydroxide. Water is consumed at the nickel electrode and produced at the hydrogen electrode, so the concentration of the potassium hydroxide electrolyte does not change. As the battery discharges, the hydrogen pressure drops, providing a reliable state of charge indicator. In one communication satellite battery, the pressure at full charge was over 500 pounds/square inch (3.4 MPa), dropping to only about 15 PSI (0.1 MPa) at full discharge. If the cell is over-charged, the oxygen produced at the nickel electrode reacts with the hydrogen present in the cell and forms water; as a consequence the cells can withstand overcharging as long as the heat generated can be dissipated. The cells have the disadvantage of relatively high self-discharge rate, i.e chemical reduction of Ni(III) into Ni(II) in the cathode: NiOOH + 0.5 H2 = Ni(OH)2. which is proportional to the pressure of hydrogen in the cell; in some designs, 50% of the capacity can be lost after only a few days' storage. Self-discharge is less at lower temperature. <ref name=Linden02>David Linden, Thomas Reddy (ed.) ''Handbook of Batteries Third Edition'', McGraw-Hill, 2002 ISBN 0-07-135978-8 Chapter 32, "Nickel Hydrogen Batteries"</ref> Compared with other rechargeable batteries, a nickel-hydrogen battery provides good [[specific energy]] of 55-60 watthours/kg, and very long cycle life (40,000 cycles at 40% DOD) and operating life (> 15 years) in satellite applications. The cells can tolerate overcharging and accidental polarity reversal, and the hydrogen pressure in the cell provides a good indication of the state of charge. However, the gaseous nature of hydrogen means that the volume efficiency is relatively low (60-100 Wh/L for an IPV (individual pressure vessel) cell), and the high pressure required makes for high-cost pressure vessels.<ref name=Linden02/> The positive electrode is made up of a dry [[sintered]]<ref>[http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980237948_1998394779.pdf Performance comparison between NiH₂ dry sinter and slurry electrode cells]</ref> porous nickel plaque, which contains [[nickel hydroxide]]. The negative [[hydrogen]] [[electrode]] utilises a teflon-bonded [[platinum black]] [[catalyst]] at a rather high loading of 7 mg/cm2, the separator is knit zirconia cloth(ZYK-15 Zircar) <ref>[http://www.azom.com/details.asp?ArticleID=3086#_Zirconia_Cloth_Battery_Separators].</ref><ref>[http://micro.magnet.fsu.edu/electromag/electricity/batteries/nickelhydrogen.html Nickel-Hydrogen Batteries]</ref> Asbestos was used in the past. ==Designs== The individual pressure vessel (IPV) design consists of a single unit of NiH₂ cells in a pressure vessel.<ref>[http://gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?1994/TM-106795.html Nickel hydrogen batteries-an overview]</ref> The common pressure vessel (CPV) design consist of two NiH₂ cell stacks in series in a common pressure vessel. The CPV provides a slightly higher [[specific energy]] than the IPV. The single pressure vessel (SPV) design combines up to 22 cells in series in a single pressure vessel. The bipolar design is based on thick [[electrode]]s, positive-to-negative back-to-back stacked in a SPV.<ref>[http://adsabs.harvard.edu/abs/1983iece....4.1568A Development of a large scale bipolar NiH₂ battery].</ref> The dependent pressure vessel (DPV) cell design offers higher specific energy and reduced cost.<ref>[http://adsabs.harvard.edu/abs/1995sert.nasa...13C 1995–dependent pressure vessel (DPV)]</ref> The common/dependent pressure vessel (C/DPV) is a hybrid of the common pressure vessel (CPV) and the dependent pressure vessel (DPV) with a high volumetric efficiency.<ref>[http://www.techbriefs.com/component/content/article/915 Common/dependent-pressure-vessel nickel-hydrogen Batteries]</ref> <gallery caption="Schematics" widths="100px" heights="100px" perrow="6"> Image:Battery workshop 1993 Fig1 Nickel hydrogen battery.jpg Image:Battery workshop 1993 Fig2 Nickel hydrogen battery.jpg Image:Battery workshop 1993 Fig3 Nickel hydrogen battery.jpg Image:Battery workshop 1993 Fig4 Nickel hydrogen battery.jpg Image:5420miller.jpg </gallery> ==See also== *[[List of battery types]] *[[Power-to-weight ratio]] *[[Pressure vessel]] *[[Timeline of hydrogen technologies]] ==References== {{Reflist}} == Further reading == * Albert H. Zimmerman (ed), ''Nickel-Hydrogen Batteries Principles and Practice'', The Aerospace Press, El Segundo, California. ISBN 1-884989-20-9. ==External links== *[http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030062140_2003070874.pdf Overview of the design, development, and application of nickel-hydrogen batteries] *[http://www.nasa.gov/offices/oce/llis/0568.html Details of the NiH₂-battery] *[http://www.electrochem.org/dl/ma/206/pdfs/1465.pdf Implantable nickel hydrogen batteries for bio-power applications] *[http://adsabs.harvard.edu/abs/1993STIN...9413265D NASA handbook for nickel-hydrogen batteries] *[http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=59267 A nickel/hydrogen battery for terrestrial PV systems] *[http://cat.inist.fr/?aModele=afficheN&cpsidt=18561599 A microfabricated nickel-hydrogen battery using thick film printing techniques] {{Galvanic cells}} [[Category:Hydrogen technologies]] [[Category:Rechargeable batteries]]'