# Ampere-hour

The ampere hour is a unit of the electric charge. Although it does not belong to the International System of Units ( SI), but is approved for use with the SI. This is a legal unit.

## Definition

A Ah is the amount of charge that flows through a conductor within one hour, when the electric current is constant 1A. It is often used to specify the available charging accumulators or batteries in ampere-hours (Ah).

The ampere hour is a multiple of the SI unit coulomb ( 1 C = 1 A · s ):

## Use in accumulators

The charge storage capacity of batteries in ampere-hours (Ah) is often understood as the (energy) capacity. However, it has to do only indirectly related to the electrical capacitance ( farads ) or with high power capacity ( watts). One should rather speak of carrier capacity or nominal charge.

Only the product of the nominal load with the terminal voltage ( volts times amps hour ) gives the energy storage capacity of a battery in watt-hours (Wh ). The nominal charge is therefore not a direct measure of the amount of energy as joules ( J), watt second (Ws) or kilowatt-hour ( kWh). But they can be used at a given voltage for estimating the period of the electrical load and to evaluate the energy capacity of the battery. The duration is proportional to the nominal load, in this case:

With

However, the actual maximum values by other factors may differ from the manufacturer's information, such as age, state of the accumulator or ambient temperature.