A comparative study on different modelling approaches in li-ion battery cooling system

Abstract

Abstract

The extensive use of simulation software has expedited the conceptual level design in various engineering fields. The automotive engineering industry has been at the forefront of developing tools to enhance the simulation-driven design of future vehicles and powertrains. To reduce carbon emissions, vehicle manufacturers have increasingly shifted towards the design and production of fully electric cars, where the battery plays a key role. The role of simulation software and virtual validation methods is of ever greater importance in electrified powertrains due to the lack of a large amount of historical data to support the design, as well as the shortened time to market for EVs. In this work, ways for fast cooling system simulation model building on two different accuracy levels are studied where one example cooling system is modeled. Thermal simulation is performed both on the module and on the battery pack level. Different variants of battery module cooling arrangements are studied via a simplified three-dimensional model. One EV battery is simulated on two different accuracy levels which both have their own strengths and weaknesses. The model with higher fidelity represents the battery module as discretized cells which allows temperature monitoring of each cell separately, hence allowing for the investigation of temperature variability inside the battery module. The simpler model, monobloc battery, represents all battery cells inside the battery as one block generating thermal energy. The simulation software CruiseM from AVL is used in the study, as it provides a simple equivalent circuit model (ECM) for the battery, and simultaneously allows simulating the temperatures in different areas of the module for prismatic battery modules. Accordingly, the effect of the internal temperature variation on the electrical properties of the battery pack can be investigated in a real-time capable model. Finally, the simple electro-thermal monobloc battery model can be coupled to a full electric powertrain model in a heavy-duty truck application, along with the cooling system. Further the effects of the power demand on thermal condition of the electrical components can be investigated to design the cooling system.