In recent years, the rate of Electric Vehicle (EV) adoption has been gradually increasing. In order for the Battery Management System (BMS) to perform effectively, accurately, and efficiently depends on the accuracy of the battery model of the battery pack. The work performed in this thesis is to model the battery pack, both the electrical model and the thermal model, using the datasheet specification from the automotive manufacturer, “Nissan Leaf.” Starting from laying the theoretical knowledge framework and battery modelling method on the software MATLAB/Simulink from the battery cell level up to the pack level architecture, after modelling the battery pack, the constant current at different C-rates is performed on the model to validate its behaviour against the real physical battery behaviours: cell voltage, pack SOC, and temperature under various current loads. The results of the simulation are aligned with the physical laws of the lithium-ion battery; the higher the C-rate, the more rapid the SOC, the terminal voltage decreases, and the higher the rise in temperature. In conclusion, the battery model of the Nissan Leaf, as presented in this thesis, can accurately describe the behaviour of the physical battery pack.