Investigation of the effect of fins added to battery cells on the performance of electric vehicle thermal management system

In this study, different types of fins are proposed to be applied to the cells to obtain better cooling performance with air for cylindrical lithium-ion batteries. Thermal conditions are important for lithium-ion batteries, and for better performance and battery life, it is desired for the cell temperature to be between 15 °C and 35 °C and for a homogeneous temperature distribution in the entire module volume without a temperature difference of more than 5 °C. Due to these restrictions, many different types of active or passive cooling methods are used in the Battery Thermal Management Systems (BTMS) of electric vehicles. In the study, fins were directly integrated into the lateral surface of the cylindrical battery cells known with the code 18650. 2 series (2S) and 4 series 3 parallel (4S3P) module configurations were numerically analyzed using the FloEFD package program for different discharge rates, cells without fins and cells with annular, square, trapezoidal, pin and mesh type fin profiles. In the numerical study, battery analyses performed according to the equivalent circuit model and thermal analysis of the system were run simultaneously, and the results showed that the fins provided benefits in the range of 2 - 4 °C in the natural convection environment and 7 - 8 °C in the forced convection environment. However, in some designs, forced convection causes temperature differences in the package over 5 °C, which is an undesirable temperature distribution for lithium-ion batteries. In the experimental study, charge-discharge experiments were performed for batteries with trapezoidal section fins, which gave the most effective results numerically, and it was observed that the finned cells reached lower temperatures compared to those without fins. The studied fin types cause an increase in the range of 150-200% for area and volume, and 33-40% for weight. Considering that temperature drops in the mentioned ranges are important for the BTMS technique and the advantages of air cooling systems such as structural simplicity, low cost and electrical safety compared to other cooling methods, it is envisaged that the proposed approach in the form of a modular fin structure can be used in engineering applications where weight and volume increases will not be a problem.