The activity of my thesis work was MiL (Model-in-the-Loop). It consisted in modeling and simulating one of the train’s subsystems, specifically the 110V auxiliary battery. The work was developed using the MATLAB/Simulink toolchain. A preliminary study was carried out to understand the type of battery, its functionality, and the corresponding sizing. In Simulink, the battery modeling workflow was implemented: I started from the creation of a single cell up to the complete battery pack, accurately modeling the battery behavior according to the required usage profile. Thanks to the measurements taken from the real battery, the reconstruction of its actual behavior became more accurate and reliable.