Electric Vehicle Battery Models Inform Crash Simulation Evaluations to Improve Real-World Safety and Reliability

In the United States, drivers rely on passenger vehicles to travel more than 3.2 trillion miles each year. The safety of vehicles during these journeys is presumed and crucial to building trust between automakers and consumers.

As adoption of electric vehicles (EVs) grows, the National Renewable Energy Laboratory (NREL) is working with Hyundai Motor Company to ensure EV batteries can go the distance safely and reliably.

Protecting passengers and the planet

Every vehicle on the market must meet strict battery safety standards and regulations to protect passengers. The Insurance Institute for Highway Safety and the National Highway Traffic Safety Administration have concluded that electric vehicles are as safe as, or even safer than, conventional vehicles. In the event of a collision, EV batteries automatically disconnect from the vehicle to reduce battery damage. Additionally, current EV designs feature a lower center of gravity, provide improved stability, and reduce the likelihood of a rollover accident. Continued research at NREL aims to further strengthen the resilience of EV batteries by improving the thermal response – or the amount of heat the battery is able to withstand – in the event of damage.

“Our goal is to understand how mechanical damage leads to battery failure and internal shorting,” said NREL researcher Anudeep Mallarapu. “Damage at the cell level tends to cause a chain reaction within the battery. However, if we manage the heat generated, we can reduce the likelihood of thermal runaway and improve overall battery safety.

Battery Abuse Simulations Inform Safer Designs

To demonstrate the safety of their vehicles, automakers perform crash assessments to develop advanced models that illustrate crash response scenarios for different vehicle models. Battery research applies this approach on a smaller scale with abuse testing.

NREL materials science researcher Anthony Donakowski prepares a battery impact test device for demonstration. Photo by Werner Slocum, NREL.

The key to designing long-lasting, reliable, and safe EV batteries is understanding the impact of damage to the battery module. With battery data in hand, NREL researchers can also develop predictive models of battery abuse that easily integrate with existing vehicle crash simulations.

“Developing models for battery-powered vehicles is complicated: in addition to the mechanical and thermal response, we also take into account the complex chemical reactions, the high-voltage implications, as well as the varied length scales and response times for different physical phenomena,” Mallarapu said.

While previous industry research focused on the progressive deformation of battery cells, NREL has introduced new capabilities to assess high-velocity dynamic impacts. This approach begins with laboratory tension and compression experiments at the component level to characterize the mechanical properties. Then, researchers use state-of-the-art equipment coupled with advanced imaging techniques to capture 10,000 to 40,000 frames per second when the cell is damaged. NREL researchers provide detailed analysis of thermal and electrochemical reactions simultaneously, measuring changes in gas and temperature distribution throughout battery failure to help inform design improvements.

“Most crashes don’t happen slowly, and battery research should reflect real-world scenarios,” Mallarapu said. “High-speed abuse testing is critical to our understanding of electric vehicle battery safety and reliability.”

NREL and Hyundai researchers are using abuse results to develop mathematical models and advanced computer simulations to streamline crash assessments for electric vehicle batteries. By validating these impact models against laboratory experiments, researchers can more quickly analyze battery response to different types of mechanical damage.

Demonstration of capabilities strengthens the partnership

NREL recently hosted Hyundai management to review the progress of the three-year collaboration and new ways of understanding failure

Mechanical research engineer Anudeep Mallarapu demonstrates NREL’s battery safety modeling and experimentation. Photo by Werner Slocum, NREL.

complex modes, physical processes and interactions that affect lithium-ion batteries.

The project team reviewed NREL’s internal experimentation capabilities as well as a newly developed toolkit for multiphysics modeling of lithium-ion batteries. Additionally, visitors experienced NREL’s advanced visualization tools to interpret mechanical, electrical, and thermal failures through simulations of battery modules under abuse conditions.

“As concerns about the fire safety of high-voltage batteries increase with the increased adoption of electric vehicles, it is essential that we develop multiphysics simulation techniques that can predict this danger in advance,” said director YongHa. Han, who heads the Virtual Technology Innovation Research Lab. in the Hyundai Motor group. “Under these circumstances, collaboration with specialist research institutes such as NREL, which has extensive development experience and capabilities related to electric vehicle batteries, is essential. We hope that the core technologies needed by Hyundai Motor Group will be effectively developed by establishing a continuous joint research and cooperation system. »

In the final phase of this collaboration, NREL and Hyundai will extend this research from battery modules to entire vehicle packs to assess how EV batteries react when multiple modules are damaged. Further research will help optimize the modeling toolbox to improve conventional crash simulation technologies and accelerate the evaluation of electric vehicle designs.

Learn more about NREL’s research on sustainable transportation and energy storage. And sign up for NREL’s quarterly transport and mobility research newsletter, Sustainable Mobility Matters, to stay up to date with the latest news.

Originally posted on NREL. By Rebecca Martineau

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