Electric current

What Is an Amp-hour? Mah, Ah

What is an amp-hour? mAh, ah

An ampere-hour is a unit of electric charge. It is represented by Ah. It is a unit that measures electric power over time. The ampere-hour is not part of the International System, since the hour is not either.

The amp-hour indicates the amount of electric charge that flows for one hour through the terminals of a battery (or an electrical conductor) providing an electric current of 1 amp (A) for one hour (h).

The ampere-hour is used to measure the capacity of a battery, that is, the amount of electricity it can store during charging and return during discharge.

A battery that has, for example, a capacity of 100 Ah, theoretically can give a current of 10 amps for 10 hours, or 1 amperes for 100 hours.

At a practical level there are certain performance losses conditioned by the battery discharge rate, the faster a battery discharges, the more energy is lost due to internal resistance. Therefore, the load capacity is usually given with reference to a standard discharge time (10 or 20 hours), and for a specific final voltage.

In the case of rechargeable batteries, Ah is an indicator of the energy charge that a battery can hold. It also will power a device before needing recharging. 

How Many Coulombs Is an Ampere-hour Equivalent?

One hour of amps equals 3,600 coulombs (amp-seconds) of electrical charge transferred to a constant current of 1 amp for 1 hour, that is. In 1 second at 1 amp, the current will flow 1 load pending.

The unit of electric charge in the International System is coulomb C. Coulomb is a derived unit that is defined in terms of the ampere: 1 coulomb is the amount of total electric charge that passes through a cross-section of a conductor through which an electric current of one ampere for one second.

Charging Capacity of a Battery. Oh and Mah

Charging capacity is the charge that a battery can store. It is measured in amp-hours (Ah). In batteries with a low charge capacity, it is usually expressed in milliampere-hour (mAh). For example those of a phone battery.

Between an 800 mAh battery or a 3,000 mAh battery, the second will last longer (twice) because it has more stored electrical charge.

Often, battery manufacturers indicate in their specifications only the charge stored in milliamp-hour (mAh). Others use only the energy stored in Wh · h (Wh).

Lithium-ion batteries are commonly used for portable electronics and electric vehicles. They have a higher mah and a better battery life.

Examples of Electrical Capacities

  • An AA size battery has a capacity of approximately 2 to 3 amp-hours.

  • The average battery of a mobile phone usually has between 2,500 and 4,000 milliamperes-hour of electrical capacity.

  • A large car has large batteries. It would have a battery capacity of about 50 amps per hour.

Table of the best phone batteries according to the OCU

Samsung M30s

6000 mAh

OPPO A5 2020

5000 mAh

Xiaomi Redmi 8 (32 GB)

5000 mAh

Xiaomi MI NOTE 10

5260 mAh

Motorola One Macro

4000 mAh

Samsung Galaxy A51

4000 mAh


    Published: May 13, 2015
    Last review: June 3, 2020