Empirical Thermal Performance Investigation of a Compact Lithium Ion Battery Module under Forced Convection Cooling

Lithium ion Batteries (LIBs) are considered one of the most suitable power options for Electric Vehicle (EV) drivetrain, are known for having low self-discharging properties hence provide long life cycle operation. To obtain maximum power output from LiBs, it is necessary to critically monitor their operating conditions. Temperature particularly, is known to directly affect the performance and life span of LiBs. This paper investigates the performance of a Battery Thermal Management Systems (BTMS) for a battery pack that houses 100 Nickel Cobalt Rechargeable 18650 (NCR18650) Lithium ion cells built as part of an electric vehicle racing development process. Thermal performance of the battery pack is investigated under three levels (1.4, 2.4 and 3.4 m/s) of air flow rate and two current rate (0.5 and 0.75C). A worst case scenario of averaged maximum cell temperature of 36.1 °C was recorded during a 0.75 C charge experiment and 37.5 °C 0.75 C discharge under the least flow rate. A reduction in maximum temperature difference of 54.28% by increasing the air flow rate in a 0.75 C charge experiment to 3.4m/s was achieved. Increasing performance with increasing airflow rate was a common trend observed in the experimental data after analyzing various experiment results. A model for the investigated battery pack was developed by training an Artificial Neural Network (ANN) utilizing the Bayesian Regularization algorithm. An R-Value of the regression plot of the overall trained model of 0.988 was achieved. The model was tested and able to predict maximum temperature values with a maximum percentage error of 10.38% for the given input data from the experiments performed. Keywords: Air-Cooled BTMS, Compact Lithium Ion Battery Module, ANN, RSM.