The potential of differential voltage analysis and electrochemical impedance spectroscopy for electric vehicles based on real-world data

As electric vehicles (EVs) become increasingly popular, battery status determination, specifically state of health (SoH), is becoming essential for monitoring aging, estimating residual value, and providing battery insurance. While onboard diagnostic methods such as electrochemical impedance spectroscopy (EIS) and differential voltage analysis (DVA) offer significant potential for in-situ SoH estimation, it remains unclear how frequently these measurements can be performed under real-world operating conditions. This study analyzes data from seven series-production vehicles, totaling 169 760 km, to evaluate idle periods and charging behavior. By modeling the SoH evolution, the study determines the achievable update intervals for each method, assessing their practical applicability for continuous battery monitoring. The results demonstrate that EIS can be effectively applied during idle periods, enabling frequent updates of the battery’s health state. DVA, in contrast, is more constrained by access to charging infrastructure, the state of charge (SoC) range, and the C-rate, but provides additional insights into specific degradation modes. The results show that EIS can be applied frequently enough during idle periods to resolve even the highest observed degradation rates at 1 % SoH resolution, providing on average 412 diagnostic opportunities per 10 000 km, whereas DVA is substantially constrained by charging behavior and SoC range, yielding only 81, roughly a fivefold reduction. Based on these findings, a hybrid strategy is recommended that combines frequent impedance-based monitoring with intermittent DVA for in-depth degradation mode (DM) analysis.