AVL Virtual Battery Development

摘要

The battery is the driving factor in all kind of modern electrified vehicles. On one hand, they essentially determine the performance and driving range. On the other hand they can make up a considerable part of the total weight and they are a significant cost factor. Additionally the battery aging defines the overall vehicle lifetime. The focus on the development for this component is correspondingly high.In order to minimize development time and costs, and to minimize or in best case avoid tedious and expensive measurements, simulation offers a decisive advantage. This already starts in the early concept phase, in which the configuration is defined to achieve high power density with the lowest total weight and at lowest possible battery costs. An important focus in the development of battery packs is the protection against the mis-use. Different abuse conditions in Lithium-Ion batteries may lead to the so-called Thermal Runaway, which releases the cell energy and the highly flammable and toxic venting gas. The thermal-runaway propagation to the neighboring cells and modules may lead to fire hazard and explosions. Hence, the propagation prevention is fundamental to meet safety requirements for electric vehicles.Although many optimization steps can be performed at the cell, module and pack level, it is clear that the behavior of a battery is very much determined by its integration into the vehicle, the operation strategy and under which climatic conditions the vehicle is operated. This influences the operational temperature and the electrochemical conditions within the cell which are responsible for the aging behavior of a battery. In modern electrified powertrains thermal, mechanical, electric and fluid domains need to be considered simultaneously in the system simulation. Additionally, the control functions for hybrid strategies or optimal battery operation are necessary. Depending on the actual state within the development process this requires the capability for multi-domain modeling with scalable modeling depth for each component.The seamless combination of system simulation with detailed component analysis and measurement data consideration is key for an efficient engineering process from concept, layout, optimization up to virtual calibration and verification.Identical electro-chemical model is available both in the 3D simulation tool AVL FIRE™ M and in the system simulation tool AVL CRUISE™ M. Thus, on the one hand, detailed 3D effects can be examined at the cell level and, on the other hand, it is possible to estimate aging effects over a very long period of time.Safety concerns are major issues that OEMs face during development and homologation of electric vehicles with Lithium-Ion Batteries. AVL FIRE™ M has the functionality to model short circuit events, thermal runaway and cell venting. The battery components are treated as a meltable solids. Hot venting gas can melt the structure and gas flow can be traced from the cell to the pack and trough the burst discs to the environment.Propagation of the gas, which contains portions of H2, CH4, CO and other flammable gases, to adjacent cells and modules can result in fire ignition. The simulation offers the possibility to evaluate the ignitability of the venting gas and to visualize the propagation of the flame front. The simulation helps to gain a better understanding of the overheating and thermal runaway processes.Among other things, different usage profiles, missions and vehicle configurations can be examined very quickly for their influence on battery life time. Operating and charging strategies can be optimized to significantly extending battery life. By connecting to a statistical aging model, it is possible to determine both the current damage to the battery and calculate when the battery reaches the end of its life.All in all, the method and workflow developed by AVL is the right solution for shortening the development time of battery systems by means of simulation, saving costs and protecting the environment.