# Ampere hour

(Redirected from MA·h)
Ampere hour
Rechargeable batteries
Top: AA battery (2500 mA⋅h)
Bottom: AAA battery (1000 mA⋅h)
Unit information
Unit system Non-SI metric unit
Unit of Electric charge
Symbol A⋅h
Unit conversions
1 A⋅h in ... ... is equal to ...
SI units    3600 C
Electrostatic units    1.079253×1013 statC
Electromagnetic units    360 abC
Gaussian units    1.079253×1013 Fr

An ampere hour or amp hour (symbol Ah; also denoted A·h or A h) 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 3600 coulombs.[1] The commonly seen milliampere hour (mAh or mA·h) is one-thousandth of an ampere hour (3.6 coulombs).

## Use

The ampere hour is frequently used in measurements of electrochemical systems such as electroplating and for battery capacity where the commonly known nominal voltage is dropped.

A milliampere second (mA·s) is a unit of measure used in X-ray imaging, diagnostic imaging, and radiation therapy. This quantity is proportional to the total X-ray energy produced by a given X-ray tube operated at a particular voltage.[2] The same total dose can be delivered in different time periods depending on the X-ray tube current.

An ampere hour is not a unit of energy. 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.[3] Generally, the battery voltage varies during discharge; an average value or nominal value may be used to approximate the integration of power.[4]

## Other measures of electric charge

The Faraday constant is the charge on one mole of electrons, approximately equal to 26.8 ampere hours. It is used in electrochemical calculations.

## Examples

• An AA size dry cell has a capacity of about 2 to 3 ampere hours.
• Automotive car batteries vary in capacity but a large automobile propelled by an internal combustion engine would have about a 50 ampere hour battery capacity.
• Since one ampere hour can produce 0.336 grams of aluminium from molten aluminium chloride, producing a ton of aluminium requires transfer of at least 2.98 million ampere hours.[5]