The battery capacity is the current capacity of the battery and is expressed in Ampere-hours, abbreviated Ah. Chemical Capacity – full storage capacity of the chemistry when measured from full to empty or empty to full. This is normally defined at a given C-rate and maximum and minimum voltages.
Current is expressed in Amps (A). It quantifies how many electrons are flowing per second. The capacity of a battery defines how much total energy is stored in each battery. The power output of a battery is how much energy a battery can give at a given time. This is a very important factor as it defines what you should use the battery for.
Since this is a particularly confusing part of measuring batteries, I'm going to discuss it more in detail. Power capacity is how much energy is stored in the battery. This power is often expressed in Watt-hours (the symbol Wh).
Power capacity is how much energy is stored in the battery. This power is often expressed in Watt-hours (the symbol Wh). A Watt-hour is the voltage (V) that the battery provides multiplied by how much current (Amps) the battery can provide for some amount of time (generally in hours). Voltage * Amps * hours = Wh.
The way the power capability is measured is in C 's. A C is the Amp-hour capacity divided by 1 hour. So the C of a 2Ah battery is 2A. The amount of current a battery 'likes' to have drawn from it is measured in C. The higher the C the more current you can draw from the battery without exhausting it prematurely.
Under well defined conditions this is often referred to as the Rated Capacity as the battery capacity is likely to be different under different temperature, discharge rates and prior use. An alternative unit of electrical charge. Product of the current strength (measured in amperes) and the duration (in hours) of the current.