Transient-boundary voltage method for measurement of equivalent circuit components of rechargeable batteries

A method is presented for measuring the equivalent circuit components of rechargeable batteries. The temporal discharge-rest-charge-rest sequence of a rechargeable battery is described, using the principles of transient circuit analysis, to derive equations for the battery voltage as a function of time during voltage transients and at the boundaries at transitions between transient phases. The equations lead to a new measurement method for battery characterization. The equivalent circuit of the battery is described as an ideal voltage source in series with a resistor and the parallel combination of a resistor and a capacitor. The battery model uses different values of resistance and capacitance, in the parallel combination, during the different phases of the discharge-rest-charge-rest sequence. The method is used to measure the circuit parameters of a nickel-cadmium battery.