State-of-charge determination of Li/SOCl2 primary battery by means of electrochemical noise measurement

Abstract

Electrochemical noise measurements were performed on a commercially available Li/SOCl2 primary battery at different state-of-charge values. Power spectral density frequency dependencies were calculated in order to ascertain their possible use for calibrating the spectral array for state-of-charge identification of sample batteries. The dependence of spectrum slope on state-of-charge value was linearly approximated to obtain the equation for recalculating the spectrum slope value into the corresponding state-of-charge value. Twenty-four sample batteries of the same type were discharged to different state-of-charge values. Following this, a state-of-charge identification test was applied for each battery and electrochemical noise was measured during short-time discharge. A calibration equation was used to calculate the state-of-charge values for each sample battery using the appropriate electrochemical noise spectrum slope value. The state-of-charge value was identified by electrochemical noise test with more than 10% precision for the majority of the batteries. For the first time, the electrochemical noise method was experimentally demonstrated to be of practical application for evaluating the condition of chemical power sources using a fully automated technique. This approach has shown competitive results when compared with electrochemical impedance and DC voltage methods.