What is C-rate of a battery?

C-rate is a measure of the rate at which the battery is to be charged or discharged relative to its capacity. The C-rate is defined as the charge or discharge current divided by the battery’s capacity to store an electrical charge. It is the theoretical current at which the battery will deliver its nominal rated capacity in one hour. But because of the internal resistance of the battery and delays in chemical processes, this is seldom materialized in actual practice. Typically, maximum capacity can be realised only at slow charging or discharging rates. Charging or discharging at faster rates can reduce the battery life.