Electro-thermal modelling of Li-ion batteries is one of the forefront topics due to the increasing interest of automotive industries in electric and hybrid vehicles. To control and manage the behavior of such batteries, reliable models are needed. In this thesis, Li-ion battery is modelled using an equivalent circuit analogy approach to study its behavior and its temperature variation under several charging/discharging tests. The model will be developed from battery cell to battery pack which is enclosed in an insulated box with air circulation to ensure temperature uniformity among its cells. First, electrical behavior is modelled using datasheet battery block found in Simulink library.