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Ampere-hour

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Unit of electric charge
ampere-hour
Rechargeable NiMH 1.2 V batteries
Top: AA battery (2500 mA⋅h)
Bottom: AAA battery (1000 mA⋅h)
General information
Unit systemNon-SI metric unit
Unit ofElectric charge
SymbolA⋅h, A h
Conversions
1 A⋅hin ...... is equal to ...
   SI units   3600 C

Anampere-hour oramp-hour (symbol:A⋅h orA h; often simplified asAh) is aunit ofelectric charge, havingdimensions ofelectric current multiplied by time, equal to the charge transferred by a steady current of oneampere flowing for one hour (3,600 seconds), thus equal to 3600 A⋅s orcoulomb.[1][2]

The commonly seenmilliampere-hour (symbol:mA⋅h,mA h, often simplified asmAh) is one-thousandth of an ampere-hour (3.6 coulombs).

Use

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The ampere-hour is frequently used in measurements ofelectrochemical systems such aselectroplating and forbattery capacity where the commonly knownnominalvoltage is understood.

Amilliampere second (mA⋅s) is a unit of measurement used inX-ray imaging, diagnostic imaging, andradiation therapy. It is equivalent to amillicoulomb. This quantity is proportional to the total X-ray energy produced by a given X-ray tube operated at a particular voltage.[3] The same total dose can be delivered in different time periods depending on the X-ray tube current.

To help expressenergy, computation over charge values in ampere-hour requires precise data of voltage: in a battery system, for example, accurate calculation of the energy delivered requires integration of the power delivered (product of instantaneous voltage and instantaneous current) over the discharge interval.[4] Generally, the battery voltage varies during discharge; an average value or nominal value may be used to approximate the integration of power.[5]

When comparing the energy capacities of battery-based products that might have different internal cell chemistries or cell configurations, a simple ampere-hour rating is often insufficient.

In other units of electric charge

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One ampere-hour is equal to (up to 4 significant figures):

Examples

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  • AnAA sizedry cell has a capacity of about 2000 to 3000 milliampere-hours.
  • An average smartphone battery usually has between 2500 and 6000 milliampere-hours of rechargeable electric capacity.
  • Automotivecar starter batteries vary in capacity but a large automobile propelled by an internal combustion gasoline engine would have about a 50-ampere-hour 12 V battery capacity.
  • Battery electric vehicle capacities are usually given in kW⋅h, but in 2013, theBMW i3 60 A⋅h was named after the capacity of one of its 96 cells, for a total of 96 × 3.6 V × 60 A⋅h =20736 W⋅h with about 18 kW⋅h usable energy, to match the number of the entry levelTesla Model S60 which had 60 kW⋅h. Later BMW i3 had 94 A⋅h and 120 A⋅h batteries, each topping Tesla's S85, S90 and S100 designations.
  • Since one ampere-hour can produce 0.336 grams ofaluminium from molten aluminium chloride, producing a kilogram of aluminium required transfer of at least 2980 ampere-hours.[6] One kilogram of aluminium commonly requires 15.37 kW⋅h, thus electric power represents about 20% to 40% of the cost of producing aluminium.

See also

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References

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  1. ^"electric charge (Symbol Q). IEV 113-02-10".electropedia.org. International Electrotechnical Commission (IEC). 2020. Retrieved2020-09-20.Note 7 to entry: The coherent SI unit of electric charge is coulomb, C. The unit ampere-hour is used for electrolytic devices, such as storage batteries:1 A·h = 3,6 kC.
  2. ^Thompson, Ambler; Taylor, Barry N. (2008).Guide for the Use of the International System of Units (SI). NIST Special Publication 811(PDF) (2nd ed.). Gaithersburg: National Institute of Standards and Technology. p. 45.To convert fromampere hour (A·h) ... to coulomb (C) ... multiply by3.6×103
  3. ^X-ray Safety Handbook, 9.0 Terms and Definitions, VirginiaTech Environmental, Health and Safety ServicesArchived July 23, 2007, at theWayback Machine
  4. ^Efty Abir, Najrul Islam (2016)."How to Calculate Amp Hours – Learn of Convert Watts to Amps". Leo Evans. Retrieved8 December 2016.
  5. ^National Research Council (U.S.) (2004).Meeting the energy needs of future warriors. National Academies Press. p. 27.ISBN 0-309-09261-2.
  6. ^T. L. Brown, H. E. Lemay Jr, "Chemistry the Central Science", Prentice-Hall, 1977ISBN 0-13-128769-9 page 562
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