Top: AA battery (2500 mA⋅h)
Bottom: AAA battery (1000 mA⋅h)
|Unit system||Non-SI metric unit|
|Unit of||Electric charge|
|SI units||3600 C|
An ampere hour or amp hour (symbol: A?h or A h; often also unofficially denoted as Ah) is a unit of electric charge, having dimensions of electric current multiplied by time, equal to the charge transferred by a steady current of one ampere flowing for one hour, or 3,600 coulombs.
The commonly seen milliampere hour (symbol: mA?h, mA h, or unofficially mAh) is one-thousandth of an ampere hour (3.6 coulombs).
A milliampere second (mA?s) is a unit of measure used in X-ray imaging, diagnostic imaging, and radiation therapy. It is equivalent to a millicoulomb. This quantity is proportional to the total X-ray energy produced by a given X-ray tube operated at a particular voltage. The same total dose can be delivered in different time periods depending on the X-ray tube current.
To help express energy, 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. Generally, the battery voltage varies during discharge; an average value or nominal value may be used to approximate the integration of power.
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.
To convert from ampere hour (A·h) ... to coulomb (C) ... Multiply by 3.6 E+03