ampeeritunti

Ampeeritunti (Ah) on unit of electrical charge, defined as the amount of charge transferred by a steady current of one ampere flowing for one hour. It is a derived unit (not a base SI unit) and is widely used to express the capacity of rechargeable batteries. By definition, 1 Ah equals 3600 coulombs.

In practice, the Ah rating indicates how much charge a battery can deliver before it is depleted. The charge Q equals current I multiplied by time t (Q = I t). To relate Ah to energy, multiply by the nominal voltage: energy in watt-hours (Wh) equals Ah times voltage (Wh = Ah × V). For example, a 3 Ah battery at 12 V stores about 36 Wh of energy.

The Ah rating is a convenient measure for estimating runtime, assuming ideal conditions. If a device draws a constant current of 1 A from a 3 Ah battery, the approximate runtime is about 3 hours (ignoring efficiency losses and aging). In real-world use, factors such as discharge rate, temperature, battery chemistry, and age reduce the usable capacity. Higher discharge rates often lower the effective capacity due to Peukert’s effect, and temperature extremes can also affect performance.

Commonly used in consumer electronics, automotive applications, and energy storage, the Ah rating helps compare batteries and estimate how long they will operate under certain loads. It is important to distinguish capacity in Ah from voltage and from instantaneous power, since energy and runtime depend on both capacity and the device’s voltage.