Patent ID: 7821232

Claim:
A method of calculating remaining capacity of a rechargeable battery, comprising: providing a system for accomplishing the following steps, the system including a microprocessor unit that reads current, voltage and calculates remaining capacity of battery; during a charging process, determining a remaining capacity of battery Qi beginning from setting an initial capacity Qc to a starting capacity then calculating a cumulative quantity of electric charge of the battery based on Coulomb's calculation (Qi=Qc+ΣI*dt); during near full terminal stage of the charging process, setting a calibration current, (Ic) instead of the charge current, (I), (Ic=(FCC−Qi)/Qe*F*I), wherein Qe=(I−Iend)/(Istart−Iend)*(FCC−Qistart) represents the predicted capacity difference in FCC, and Iend represents a cut off current for determining a charging termination, Istart and Vcstart represent a starting current and voltage respectively when the calibration starts, and capacity is Qistart at that time, F is an adjustable parameter (1/F=Aa*(I−Iend)/(Istart−Iend)+Bb, wherein Aa,Bb<=1), FCC is a full charge capacity of the battery; and calculating, using the microprocessor unit, the remaining capacity by Qi=Qi−1+Ic*dt or alternatively by Qi=FCC−Qe, so that Qi approaches FCC at the full charge terminal stage, wherein Qi−1 represents the remaining capacity before a time interval dt pass.