This grade thesis will explain the powertrain of the CAT15X, the 2023 season Formula Student single-seater from the BCNeMotorsport team. It covers wiring, inverter, and motors, with a particular emphasis on the new battery designed and manufactured this season. Firstly, the various tests that the car undergoes during competitions will be explained. Competitions involve not only running the car but also passing inspections for the car to be in R2D condition. There are also statics tests, which do not involve the speed of the car and focus on explaining different parts of the car in detail, and projects presentations. The powertrain consists of different parts, and to understand all the sizing done for the car, it is essential to dedicate a section to each component of the powertrain, from the cells that generate energy to the wheel assembly. One of the most important parts of the competion is the Formula Student regulations. It is crucial to spend time reading them and to pay close attention to changes made during the season, as they can require a complete redesign of a part of the car.