EV battery diagnostics can use techniques such as electrochemical impedance spectroscopy and differential voltage analysis to assess battery health during vehicle operation.
Researchers at the Technical University of Munich have analyzed nearly 170,000 km of real-world electric vehicle (EV) data to determine how frequently advanced battery diagnostic techniques could realistically be performed onboard production vehicles.
The study examined seven series-production EVs over a combined 169,760 km, focusing on electrochemical impedance spectroscopy (EIS) and differential voltage analysis (DVA).
Both techniques can provide information about battery state of health (SoH), but each requires specific operating conditions before useful measurements can be collected.
EIS measures a battery’s response to electrical excitation across different frequencies and can provide information related to internal resistance and aging. The researchers evaluated whether normal vehicle idle periods provide enough opportunities for those measurements to be performed regularly throughout an EV’s operating life.
Their analysis identified an average of 421 potential EIS diagnostic opportunities per 10,000 km. The researchers found that this frequency was sufficient to track even the highest observed degradation rates at a resolution of one percentage point of SoH in more than 75% of the investigated cases.
DVA relies on battery voltage behavior during charging and can provide additional information about specific degradation mechanisms. Its availability was more restricted because suitable measurements depend on charging behavior, the battery’s state-of-charge window, and charging rate.
The study identified an average of 81 potential DVA measurements per 10,000 km, approximately one-fifth the number available for EIS. DVA was better suited to less-frequent diagnostic measurements during charging events where the required operating conditions were met.
The researchers found that selecting an appropriate state-of-charge range for the diagnostic method had a greater influence on measurement availability than shorter relaxation periods or low charging rates.
The study analyzed real-world data from seven EVs covering 169,760 km to evaluate when electrochemical impedance spectroscopy (EIS) and differential voltage analysis (DVA) could be performed during normal vehicle operation. (Image: Urban et al., eTransportation, CC BY 4.0)
The results point toward combining the two techniques rather than relying on either method alone. Frequent EIS measurements could provide regular SoH updates during vehicle idle periods, while DVA could be performed during suitable charging sessions to provide additional insight into how the battery is degrading.
“Our conclusion: a hybrid strategy. Impedance-based measurements provide high-frequency SoH updates during idle periods, while DVA resolves specific degradation modes during suitable charging events,” said Raphael Urban, lead author of the study.
“Based on these findings, a hybrid strategy is recommended,” the researchers wrote, combining frequent impedance-based monitoring with less-frequent DVA for deeper degradation analysis.
The research was published in eTransportation and was conducted by Urban and colleagues from the Technical University of Munich.
Resources
Raphael Urban et al., “The potential of differential voltage analysis and electrochemical impedance spectroscopy for electric vehicles based on real-world data,” eTransportation, Vol. 29, 2026, Article 100619. Published by Elsevier on ScienceDirect. 10.1016/j.etran.2026.100619.
Filed Under: Batteries, Technology News