State of health estimation of Li-ion battery
Paul, Smita Rani (2024)
Diplomityö
2024
School of Energy Systems, Sähkötekniikka
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe20241216102821
https://urn.fi/URN:NBN:fi-fe20241216102821
Tiivistelmä
Li-ion batteries are used in a wide range of applications, including electric vehicles and portable electronics due to their high energy density and voltage. Accurate estimation of the state-of-health of batteries is crucial for optimizing their performance, longevity, and safety.
This thesis presents a state-of-health estimation method based on incremental capacity analysis. This study analyses the effect of varying current and temperature on different Li-ion battery cells. Experimental data were collected from various Li-ion battery cells subjected to different operational temperatures (5℃, 23℃, 35℃ and 45℃) and currents (0.15 A, 0.5 A, 1.25 A and 4.0 A). At lower currents, three clear peaks were observed in the incremental capacity curve, while at higher currents, only two distinct peaks were detected. The results indicate significant dependencies on both temperature and current. Accelerated battery degradation was found at elevated temperatures, where all the batteries were cycled at the same 4.0 A current. Capacity loss was much faster at 5°C cycling, highlighting the importance of considering thermal factors in the state of health estimation. Direct use of the changes in incremental capacity, peak areas does not provide accurate estimate for the battery state-of-health. However, if linear fit can be made to correlate the peak areas to the actual remaining capacity, much more accurate estimates can be made. This finding provides valuable insights for the development of battery management systems and the optimization of Lithium-ion battery usage in real applications. This study also analyses the correlation between measured and calculated capacities.
This thesis presents a state-of-health estimation method based on incremental capacity analysis. This study analyses the effect of varying current and temperature on different Li-ion battery cells. Experimental data were collected from various Li-ion battery cells subjected to different operational temperatures (5℃, 23℃, 35℃ and 45℃) and currents (0.15 A, 0.5 A, 1.25 A and 4.0 A). At lower currents, three clear peaks were observed in the incremental capacity curve, while at higher currents, only two distinct peaks were detected. The results indicate significant dependencies on both temperature and current. Accelerated battery degradation was found at elevated temperatures, where all the batteries were cycled at the same 4.0 A current. Capacity loss was much faster at 5°C cycling, highlighting the importance of considering thermal factors in the state of health estimation. Direct use of the changes in incremental capacity, peak areas does not provide accurate estimate for the battery state-of-health. However, if linear fit can be made to correlate the peak areas to the actual remaining capacity, much more accurate estimates can be made. This finding provides valuable insights for the development of battery management systems and the optimization of Lithium-ion battery usage in real applications. This study also analyses the correlation between measured and calculated capacities.