Electric and hybrid vehicles are becoming increasingly popular among environmentally conscious consumers, significantly impacting the automotive industry and the development of battery technologies. Fast diagnostic solutions are becoming critical as battery systems wear out over time and performance degrades. This study aims to investigate the battery system of a dedicated electric vehicle, the Toyota Prius, and its condition diagnostics. The test was performed by querying and saving the data using a custom Arduino-based specific measurement tool. The battery modules in the system were tested separately during the evaluation. During the condition assessment, the deviation from the average voltage of different sizes is analyzed and weighted individually depending on the size of the deviation. The analyses also cover more static and dynamic driving styles. The results show the influence of the driving style on the module voltage deviation. Furthermore, the method allows the detection and localization of weak battery modules in the system.