C/2 = 0.5C C/5 = 0.2C C/10 = 0.1C C/20 = 0.05C how to use this calculator? 1 - Enter the battery capacity and select the unit type. For example, If you have a 50 amp hour battery, enter 50 and select Ah. 2 - Enter the battery c-rating number (mentioned by the manufacturer on the specs sheet of your battery). ...