This manuscript discusses the development of a 3D thermal model for a power-split hybrid powertrain, including its battery modules and power electronics. The 3D model utilizes a finite differencing (FD) heat transfer algorithm, complemented with experimental boundary conditions. The experimental setup is configured to acquire the battery current, voltage, and its inner and surface temperatures in discrete and in full-field scans. The power-split hybrid configuration is tested using a standard and artificial driving cycles. A battery resistance model is then used to couple the experimental boundary conditions with the finite differencing code, which employed a cell-based internal heat generation model to describe the pack chemical reaction mechanism. This study presents a complete analysis based on battery current and voltage in relation to vehicle speed. The proposed model also predicts the powertrain spatial and temporal temperature profiles in agreement with the vehicle actual conditions as indicated by the On-Board Diagnosis (OBD) module.