Battery Impedance Measurement Using Fast Square Current Perturbation

This paper proposes a simple but accurate battery impedance measurement method. Unlike other complicated and expensive strategies, the proposed method only need a MOSFET and a resistor. A square current perturbation will be generated by the proposed circuitry and a voltage response across the tested battery can be obtained. Bases on the voltage and current signals, Discrete Fourier transform is used to calculate the impedance at fundamental and odd harmonic frequencies. The feasibility of the proposed method has been verified by simulation and experiments. The error of the proposed method is less than 5% at 80% SoC (state of charge) compared with the conventional small AC (alternating current) signal injection method.