State of Charge

State of charge (SoC) quantifies the remaining capacity available in a battery at a given time and in relation to a given state of ageing. It is usually expressed as percentage. An alternative form of the same measure is the depth of discharge (DoD), calculated as 1 − SoC. It refers to the amount of charge that may be used up if the cell is fully discharged. State of charge is normally used when discussing the present state of a battery in use, while depth of discharge is most often used to discuss a constant variation of state of charge during repeated cycles.