Small-Perturbation Electrochemical Impedance Spectroscopy System With High Accuracy for High-Capacity Batteries in Electric Vehicles

• Published in: IEEE transactions on industrial electronics (1982) pp. 1 - 11
• Main Authors: Lee, Young-Nam, Jo, Seong-Won, Rahim, Gul, Lee, Sang-Gug, Kwon, Kyeongha
• Format: Journal Article
• Language: English
• Published: IEEE 05.09.2024
• Subjects: Accuracy; Batteries; Battery charge measurement; Battery management; Current measurement; electric vehicles (EVs); electrochemical impedance spectroscopy (EIS); excitation current; Impedance; lithium-ion batteries; Resistors; Voltage measurement
• ISSN: 0278-0046; 1557-9948
• DOI: 10.1109/TIE.2024.3436676

This article presents an electrochemical impedance spectroscopy (EIS) system optimized for high-capacity electric vehicle (EV) batteries, prioritizing high measurement accuracy with minimal current perturbation while reducing measurement time. The system incorporates a switched-resistor high-pass filter for accurate ac voltage measurement and a low-noise amplifier for signal amplification. It also features two parallel low-pass filters with tailored bandwidths (0.2 Hz for 1-9 Hz and 1 Hz for 10-1 k Hz), significantly enhancing accuracy and reducing settling time. In addition, the small current perturbation approach improves safety and simplifies the analysis process. Our prototype achieves precise impedance measurement with a standard deviation of less than 10.4 μ Ω for high-precision resistors and less than 14 μ Ω root-mean-square error in magnitude for a 70 Ah battery across 1-1 k Hz frequency range and 20-80% state-of-charge range at 25◦C temperature. These findings demonstrate the proposed EIS system's effectiveness in the accurate assessment and health monitoring of large EV batteries.