Experimental and Numerical Studies on Battery Temperature Distribution

Accurate temperature measurement and thermal management of lithium-ion batteries are of utmost importance nowadays because of their significant influence on battery performance, cycle life, battery degradation, safety etc. But measurement of battery core temperatures on electric vehicles in real time is a challenge due to the complex design and microstructure of the cell. So, the onboard diagnostic systems measure cell skin temperatures and use correlation algorithms to estimate thermal distribution. But the battery skin temperature does not exactly reflect the battery core temperature and the uncertainties are to be overcome with complex estimation algorithms. In the current work, detailed experimental studies were conducted on M50 21700 cylindrical cell to determine voltage and temperature characteristics with different discharge rates at ambient temperature. Using the test data, a 1-D coupled thermal electrochemical model of cell was built and validated which can predict battery voltage and average cell temperature for different operating conditions. Then a 3D CFD model of the cell is developed using the thermal parameters of the 1D model and the lumped heat generation terms are ported from 1D to 3D using a coupled approach. The 3D model is validated by the comparison of temperature with 1D. From the tests, temperature difference between cell core to outer skin is measured and the temperature gradient is imposed on the 3D model by tuning the thermal parameters. The 3D CFD model when extrapolated into cell and module level helps to analyze the heat transfer and temperature distribution for different coolant flow rate conditions. The developed approach can also help onboard thermal management algorithms to make better estimation of battery temperature which would help in efficient battery cooling and managing safety.