Broadband Impedance Acquisition of Lithium-Ion Batteries Using Spectrum-Controlled Ternary Sequence

Electrochemical impedance spectroscopy provides useful information for battery state estimation, yet conventional signals are often limited by low signal-to-noise ratio (SNR) and inefficient utilization of excitation power. Motivated by this, we propose a spectrum-controlled ternary sequence. By employing logarithmic frequency distribution and amplitude weighting, the proposed sequence concentrates excitation energy in the critical mid-to-low frequency bands to improve the SNR. Meanwhile, an absolute available power criterion is incorporated into an iterative phase-updating and adaptive quantization process to maximize the available signal power. Post-acquisition, a power-weighted adaptive edge-preserving filter is developed for impedance filtering. The proposed method outperforms the conventional methods across different battery types, states of charge, states of health, and ambient temperatures. Experimental results demonstrate that broadband impedance data covering the frequency range from 0.22 Hz to 3.15 kHz can be obtained within 4.68 s, with a maximum normalized root mean square error below 0.40%.