| 主权项 |
1. A method of determining the state of charge of a rechargeable battery comprising the steps of:
calculating the DC impedance of the battery by:
performing a first constant current discharge of the battery at a first C-rate; measuring the voltage and current during the interval of the first constant current discharge and calculating the amount of charge extracted from the battery up to a point i, whereby the battery voltage drops to a threshold value; calculating the state of charge as being equal to (((Qmax−Qi))/Qmax)×100, where Qmax is the total charge extracted from the battery, and where Qi is the amount of charge extracted at the point i; performing a second constant current discharge of the battery at a second C-rate lower than the first C-rate; measuring the voltage and current during the interval of the second constant current discharge and calculating the amount of charge extracted from the battery up to the point i, whereby the battery voltage drops to a threshold value; calculating the state of charge as being equal to ((Qmax−Qi))/Qmax)×100, where Qmax is the total charge extracted from the battery, and where Qi is the amount of charge extracted at the point i; and
calculating the DC impedance of the battery, for a given state of charge as being: ((Vbatsecond C-rate−Vbatfirst C-rate)/(Iloadfirst C-rate−Iloadsecond C-rate), where Vbatsecond C-rate and Vbatfirst C-rate are the battery voltages measured at the second C-rate and the first Crate, respectively, and where Iloadsecond C-rate and Iloadfirst C-rate are the current load when discharging at the second C-rate and the first C-rate, respectively. |
