本論文提出一個可以在線式量測鋰離子電池內阻的手持式系統架構,可以在鋰離子電池動態變化時量測出內阻,以及應用在電動車與鋰離子電池需要動態量測之相關應用場合;運用內阻可以用來推測電池殘電量與電池壽命。此系統架構採用交流內阻量測法,量測頻率為1kHz;根據電化學阻抗譜,使用電池等效電子電路模型來描述電池內部複雜的化學反應;將微小的正弦波激勵訊號注入電池,透過觀察電池的響應訊號,再經過計算而得到電池內部阻抗,而激勵訊號在1kHz時,阻抗角為零度,故為實部阻抗,在計算上則不需要考慮相位差的問題。本論文採用純交流的正弦波電流激勵訊號,優點在於純交流的正弦波電流,在量測時較不會產生消耗或影響電池的狀態。本系統以微控器搭配所設計的各級硬體電路,及使用四線式量測減少線材對量測訊號的影響,提升量測之精準度,經由類比數位轉換器量測出訊號,再由微控制器計算出電池內阻,並在LCD上顯示出電池內阻與電池電壓以提供使用者參考。
This paper proposes a portable online measurement system architecture for internal resistance in lithium-ion batteries that uses internal resistance for estimating state of charge (SOC) and state of health (SOH), as well as its application in electric vehicles where dynamic measurement for lithium-ion batteries is required. Based on the electrochemical impedance spectroscopy (EIS), an equivalent circuit model for batteries is used to describe complex chemical reactions inside batteries. Internal impedance in the battery is calculated and obtained by injecting a small sine wave excitation signal into the battery and observing the response signal from the battery. The proposed architecture uses pure AC sine wave excitation signals because of the advantage that pure AC sine wave current is less likely to generate consumption or affect the battery state during measurement. With a micro controller unit (MCU) in combination with purpose-built hardware circuits at all levels and the use of four-wire measurement that prevents wires from affecting measurement signals. Calculation of internal resistance in the battery via the MCU and finally displaying internal resistance and voltage in the battery on the LCD for users to refer to.