C-rate

C-rate is the rate at which a battery is charged or discharged relative to its capacity, where 1C empties the battery in one hour and 0.5C empties it in two.

For a storage system the same idea is the ratio of power rating to energy capacity: a 1 MW, 4 MWh battery runs at 0.25C and has a four hour duration. Higher C-rates stress cells, heat them, and age them faster, so battery warranties cap the C-rate as well as the depth of discharge. The battery management system publishes the current allowed charge and discharge power, and the energy management system never exceeds it.