amperehoras

Ampere-hour, abbreviated Ah, is a unit used to express the electric charge capacity of a battery or storage device. It represents the amount of charge transferred when a constant current of one ampere flows for one hour.

In terms of fundamental units, 1 Ah equals 1 ampere × 1 hour, which is 1 A × 3600 seconds = 3600 coulombs. The ampere-hour is convenient for describing battery capacity, but it is not an SI unit; the SI unit of electric charge is the coulomb.

Battery capacity is commonly specified in Ah or milliampere-hours (mAh). Typical values vary by device: smartphone batteries often range from about 3 to 5 Ah, while car batteries are around 40 to 100 Ah. These figures indicate how much charge a battery can deliver at a given current before it is exhausted, under specified operating conditions.

The energy stored in a battery depends on both its charge capacity and its voltage. Energy in watt-hours equals Ah × voltage (V). For example, a 2 Ah battery at 12 V stores about 24 Wh of energy. A battery with the same Ah rating but higher voltage stores more energy.

Important caveats: Ah measures charge, not instantaneous power or total energy. Two batteries with the same Ah rating can hold different amounts of energy if their voltages differ. The Ah rating can also change with discharge rate, temperature, and battery chemistry.