Battery capacity is the amount of charge stored in a battery, expressed in ampere-hours (Ah). Battery capacity is a measure of the maximum amount of energy that can be obtained at a given voltage (V).
Thus, a battery’s stored energy is the product of Ah and V, which is equal to watt-hours (Wh). Generally, a residential solar system generates several thousand Wh. Hence the kilowatt-hour (kWh) is a common unit of measurement for solar battery storage.
Battery capacity is determined by the amount of active material within the battery. However, the capacity stated by a manufacturer is an ‘ideal’ number. It is often used for comparison purposes.
In reality, capacity depends on many factors. Such as its age, past history, the charging and discharging pattern and its temperature.