Fast impedance measurement method for large capacity batteries using chirp and filtered pseudo-random binary sequence

Abstract

Fast impedance measurement with well-constructed excitation signals is crucial for battery internal states analysis and faults diagnosis. The pseudo-random binary sequence (PRBS) is a promising time-efficient excitation signal, but it lacks power content in the low-frequency range and is susceptible to high-frequency harmonics beyond the measurement limits, especially for square large-capacity batteries. Motivated by this, this paper proposes a novel parallel-connected signal derived from filtered PRBS and chirp sequence to boost low-frequency components while mitigating high-frequency effects. Meanwhile, to enhance accuracy in measuring square large-capacity batteries with low impedance, the paper introduces a differential amplification circuit to improve voltage response robustness against noise. Experimental results confirm the effectiveness of this method, achieving precise impedance measurements across the 0.1 Hz–1000 Hz range in just 10.24 s. With different states of charges, temperatures, and battery types, errors of the measurement are below 3.67 %.