The total battery capacity is found by comparing states-of-charge before and after applying the load with the amount of charge passed. When an applications load is applied, the impedance of the cell is measured by comparing the open circuit voltage (OCV) obtained from a predefined function for the present state-of-charge with the measured voltage under load.

Measurements of OCV and charge integration determine the chemical state-of-charge (SOC) and chemical capacity (QMax). Ra is the impedance of the cell at 25°C at various states-of-charge.

The BQ27Z746 acquires and updates the battery-impedance profile during normal battery usage. It uses this profile, along with the state-of-charge and QMax value, to determine FullChargeCapacity() and RelativeStateOfCharge() specifically for the configured load and present temperature. FullChargeCapacity() reports a capacity or energy available from a fully charged battery reduced by Reserve Cap-mAh or Reserve Cap-cWh under the configured load and present temperature until Voltage() reaches end-of-discharge voltage (EDV).