The ampere-hour (Ah), milli-ampere-hour (mAh) or ampere- second( As) is a unit of measurement from the system of units for the amount of charge of batteries, i.e. their nominal capacity. One ampere-hour (Ah) corresponds to 3,600 ampere-seconds (As) or 3,600 coulombs (C).
The ampere-hour parameter corresponds to the nominal capacity of batteries or rechargeable batteries. It is calculated from the product of the current (I) and the time (t) and tells how long a battery or charged accumulator can be discharged with which current. This value is the C coefficient.
For example, if a NiCd battery has a rated capacity of 1,500 mAh (milli-ampere hours), then it can deliver a current of 5 mA for 300 hours. A lead-acid battery with a rated capacity of 120 Ah can deliver 1 A for 120 hours or 0.5 A for 240 hours, or a coin cell with a battery capacity of 30 mAh can deliver a continuous current of 10 µA for 3,000 hours.