Thermal and performance modeling of electric vehicle batteries [Elektrikli araç bataryaları için sıcaklık ve performans modellenmesi]

Electric vehicles have great potential to reduce transport related emissions and costs. However, there are still some barriers that need to be overcome to ensure the widespread use of these vehicles. Some of these barriers are the limited driving range and battery life of the vehicles. Driving range and battery life vary depending on the design of the battery and the materials used, and batteries of the same design may show different behavior according to the conditions of use. One of the most important factors affecting driving range and battery life is temperature. Therefore, temperature should also be considered when modelling battery behavior. Battery performance modelling aims to calculate the timedependent change of current and voltage profiles during driving and charging of the vehicle. To perform these calculations, the electrical dynamic behavior of the battery needs to be modelled. However, this behavior changes with temperature. Therefore, these models should also be combined with a thermal model. In this study, a performance model for different types of lithium-ion batteries, which can also account for temperature variation, is developed. The modelling is done using an equivalent circuit model. For different lithium-ion battery types, the equivalent circuit parameters differ. In addition, each parameter is time dependent with respect to temperature and state of charge of the battery. The construction of this model involved determining the parameters for each battery type and formulating their dependence on temperature and state of charge. Furthermore, the energy dissipated as heat in the circuit represented by the equivalent circuit model was calculated as a function of current and voltage. These models were created separately for plug-in hybrid vehicles and battery electric vehicles. Since the drivetrain, as well as the amount of power and energy required by these two vehicle types are different, battery designs also differ in terms of the number of cells, electrical and physical connection techniques of the cells. Using the developed models, the behavior of three different types of vehicle batteries under two different driving cycles is calculated. In preliminary studies, it has been observed that the temperature rise of the all-electric vehicle battery can be as low as 1oC. In plug-in hybrid vehicles, an increase of up to 50oC was observed. The results show differences according to battery size, type, ambient temperature and driving cycle. In this study, these differences are compared, and suggestions are made regarding the battery cooling system design