In the present study, the battery thermal management of a series hybrid electric vehicle is modeled and optimized for different standard driving conditions. The heat generation of the battery is comprehensively studied in previous works for the steady-state charge or discharge of the battery. Despite the previous investigations, the heat generation. The automotive industry is shifting to electric and hybrid electric vehicles due to the environmental issues of conventional internal combustion engine vehicles, fossil fuels, strict emission laws, encouraging policies, and improvement in high-efficiency batteries. The biggest hurdle in developing HEVs and EVs is energy storage,. Li-ion batteries are employed in electrified vehicles due to the long life cycle, high energy capacity, and energy density. The operating temperature considerably affects the high voltage batteries' life, safety, and performance. The appropriate operating temperature range for batteries is 15– to 35 °C. Therefore, cooling, heating, ventilating, and insulating the batteries is necessary to achieve the desired operating temperature. Different BTMS configurations are proposed by researchers. Air-cooled, liquid-cooled, PCM type, heat pipe type, and thermoelectric type are different categories of BTMS. From another perspective, BTMS can be clustered into passive, active, and hybrid systems. The passive system normally utilizes PCM,,, heat pipe, or air convection that consumes minimum power. Hybrid systems implement both advantages of passive and active systems. Air-cooled systems usually are less expensive and more complicated than other BTMS configurations. This type is implemented in vehicles with low cooling demand for batteries. On the other hand, active liquid-based systems are the most popular BTMS configuration in the automot. Battery thermal management system (BTMS) has a crucial role in the battery life cycle (BLC) and the energy consumption of hybrid electric vehicles (HEVs). In the present study, the BTMS model is created with comprehensive details of all components to investigate the effects of design parameters on the total customer ownership (TCO). The present stu. A plug-in series hybrid electric vehicle is developed and made by Irankhodro Powertrain company and is shown in Fig. 4. Lots of driving tests are defined for the vehicle to evaluate design parameters. To evaluate vehicle energy consumption, different real driving conditions including high traffic jams, steep roads, highways, and different ambient temperatures, are defined in the driving cycles.The combustion engine is set off for accurate energy consumption measurements in all driving tests.In the present study, the total cost of ownership (TCO) is considered the objective function to optimize the initial and operational cost of BTMS. A genetic algorithm, especially NSGA III, is implemented to minimize TCO by considering cost-effective variables. The initial random population with 20 different configurations is generated first. The ob.