This thesis work discusses the detailed design of the Traction Battery of the 2018 FSAE season car, a project on which I have been working as Technical Director of the PoliTO racing team in the academic year 2017-2018. The starting point for the car development was the analysis of the weaknesses of the previous car, with a focus on the improvement of the vehicle handling, aerodynamic, control as well as on weight reduction. The Traction Battery resulted to have a huge impact on the vehicle weight and packaging. A new design has been crucial to lower the center of gravity and allow the integration of a diffuser which increased the vehicle downforce.