Embedded Broadband EIS Measurement System Based on Lithium-Ion Battery DC–DC Converter

Accurate, online wide-frequency electrochemical impedance spectroscopy (EIS) measurement is essential for real-time state estimation and early fault detection of lithium-ion (Li-ion) batteries. However, conventional online EIS methods rely on external signal generation equipment and are limited by the bandwidth of traditional proportional-integral (PI) controllers, causing high-frequency distortion and low accuracy. Therefore, an embedded EIS measurement system based on Li-ion battery dc–dc converter is proposed, featuring a duty ratio compensation PI (DRC-PI) control strategy. By designing a duty ratio function and decoupling EIS measurement from charging control through digital filtering, the proposed method achieves accurate, real-time wide-frequency EIS measurements without additional hardware. Experimental results show that, compared to traditional PI control, the DRC-PI control extends the EIS frequency range from 0.1 Hz–2.8 kHz to 0.1 Hz–25 kHz, reduces the maximum normalized root mean square errors (RMSEs) from 6.32% to 1.56%, and shortens the measurement time from 448.43 to 60.78 s compared with commercial electrochemical workstations. These improvements verify the method’s potential for embedded, high-precision battery diagnostics and online safety management.