The nominal capacity (or rated capacity) of a storage is the amount of energy that could be withdrawn from it at a particular constant current, starting from a fully charged state. The current used to rate batteries varies from one manufacturer to another, but it is typically either the 10-hour, 20-hour, or 100-hour rate. The 10-hour rate (C10) is the current that causes the storage to be drained after 10 hours.
See also