Discussion on the application of ANSYS in the simulation design of new energy batteries

Recently, Mercedes-Benz solemnly announced that it will electrify its entire automobile product line by 2022, and stop production and sales of traditional fuel vehicles. Previously, Volvo also announced that it will transform its entire product line into electrified by 2019. Major manufacturers have set their sights on the field of new energy vehicles in response to the increasingly stringent emission standards of various countries. As of now, six countries in the world have publicly stated that they will completely ban pure gasoline and diesel vehicles. The Netherlands and Norway proposed to ban the sale of fuel vehicles after 2025, Germany proposed to allow only zero-emission vehicles to be on the road after 2030, the United Kingdom proposed to completely ban the sale of gasoline and diesel vehicles from 2040, and India plans to completely ban the sale of fuel vehicles in 2030. The new policies of various countries will accelerate the market of new energy vehicles.

As new energy vehicles become the development trend of the automotive industry, major automobile manufacturers have stepped up their efforts to support the research and development of new energy vehicle technology. In the transformation and upgrading of research and development and production, various new energy vehicle companies have gradually realized that batteries, as one of the core components of electric vehicles , have become one of the bottlenecks restricting the development of electric vehicles due to their comprehensive performance and lifespan, which seriously affect the performance of the entire vehicle. It is also the key to reflecting technical strength. The shortcomings of automotive power battery technology, short driving range, long charging time and other problems hinder the widespread popularization of electric vehicles. In order to solve the problems of battery energy storage , driving range, fast charging and other aspects, more and more scientific research institutes and automobile companies have joined the research and development of automotive power batteries, trying to break through bottlenecks and create longer driving range. Since the beginning of this year, there have been reports at home and abroad that BMW, Ford, Jaguar and Land Rover will jointly establish a battery production plant for electric vehicles . In addition, Volkswagen of Germany also has such plans. In addition, Tesla 's $5 billion super battery factory is about to be put into production, and a large number of domestic vehicle companies including SAIC, BAIC, Chery and Lifan have also extended their business to the field of power batteries in various ways to varying degrees. The market is expanding rapidly. While many automakers are accelerating the launch of new energy vehicles, they are also gradually beginning to develop power batteries, and the power battery market is experiencing changes. At the same time, due to the characteristics and requirements of power batteries, such as small size, high specific energy, and long cycle life, many automakers are facing many problems in the design and development of power batteries, and the main challenges include the following aspects:

① Cost: Batteries, motors, and electronic control systems are the three most critical components of new energy vehicles, accounting for more than 60% of the cost of new energy vehicles. Therefore, how to save manufacturing costs while ensuring performance has become the top priority;

② Performance: Considering the limitation of space layout, the battery is small in size. At the same time, considering the battery life requirement, the battery is required to have high specific energy. The thermal performance and stability of the battery have become the key issues that designers need to consider;

③ Durability and service life: Automobile driving conditions are complex, and the power battery needs to be tested under various complex conditions, such as random vibration, fatigue durability, etc., to ensure that the car can meet the overall service life;

④Safety: As the main means of transportation for humans, cars must not only ensure the performance of the battery pack itself, but also consider safety in harsh environments. For example, preventing heat problems such as high-temperature combustion is a concern for many car companies.

In summary, the design of power batteries is a complex, multi-scale problem involving materials science, electrochemistry, structural design, heat dissipation design and many other aspects. The safety of batteries for electric vehicles has been based on two relevant industry standards. On May 15, 2015, the national standard GBT31467.3-2015 for lithium-ion power battery packs and systems for electric vehicles, drafted by the National Technical Committee for Automotive Standardization, was officially released. This standard has detailed provisions for the experimental items of power batteries. At present, in most power battery manufacturers, the design method for power batteries is usually from design to experiment and then to design modification, which usually requires multiple rounds of revisions, resulting in long design and experimental cycles, high experimental costs and other problems, which directly lead to a long delay in the time to market of products, thus missing opportunities in today's fiercely competitive battery field.

Therefore, this paper intends to combine relevant standards and simulation platforms through simulation methods and apply them to the design and development process of power batteries, so as to help enterprises intervene in product development in the early stages of design, find the best combination of product design parameters through simulation, design products with the best comprehensive performance, realize lean production, control product quality, and thus enhance corporate competitiveness.

ANSYS simulation platform solutions in the field of power batteries

As mentioned above, due to the complexity of power battery design, problems of different scales and levels such as strength, fatigue, heat, and electrochemistry will arise, so multi-field and multi-level simulation work is required, so the coordination of simulation data becomes extremely important.

As the world's leading multi-physics simulation tool, ANSYS uses Workbench as a multi-physics simulation platform to establish a simulation system, realize data sharing and collaborative simulation, and can easily simulate power batteries at different scales. (As shown in the figure below).

Figure.1 ANSYS simulation capabilities for power batteries at different scales

Taking the design of battery pack as an example, GBT31467.3-2015 has fully specified its structural performance requirements. Usually, a complete experiment takes a long time. If the experiment fails, it needs to be modified and re-tested. Therefore, based on the ANSYS platform, the experimental conditions specified in the specification can be simulated to find out the weak points of the product and perform optimization analysis, which can save a lot of time and cost. The main experimental conditions and corresponding simulation types in the specification are summarized in the following table.

ANSYS application cases in battery simulation

1. Battery Pack Random Vibration Simulation Case

A random vibration analysis is performed on a certain type of battery pack to check the structural performance of the battery pack. The geometric model of the battery pack is shown below. Before the simulation, the ANSYS model repair tool Spaceclaim is used to repair and simplify the model to reduce the amount of calculation without affecting the accuracy. By performing modal analysis and random vibration analysis on the battery pack, the stress state of the product under 1sigma probability is checked to meet the specification requirements.

2. Battery Pack Drop Analysis

For a certain type of power battery, the drop condition is investigated. The drop analysis generally adopts the explicit dynamic analysis method. In this analysis, the Explicit Str module is used for analysis, considering drops at different heights and angles, and finally the stress and deformation of the power battery under different conditions are obtained.

in conclusion

Through multi-physics and multi-scale simulation based on the ANSYS Workbench platform, comprehensive simulation work can be performed on various battery performances. At the same time, this method has the following advantages:

(1) ANSYS Workbench has a collaborative simulation environment, which avoids data heterogeneity problems and meets the requirement for unified simulation environment;

(2) Using simulation methods to analyze various performance of battery packs can greatly shorten the product development cycle and reduce experimental costs;

(3) For the development of new products, if there is a lack of experience, simulation methods can be used to compare multiple solutions and formulate the best solution for practice.