Temple University Mechanical Engineering Professor Elham Sahraei’s SAHRAEI failure criteria is the first tool to estimate the probability of an EV battery failure allowing to make electric vehicles lighter and safer.
Elham Sahraei, associate professor in Temple’s Department of Mechanical Engineering, has spent more than a decade researching lithium-ion batteries mechanical damage.
Photo by Ryan S. Brandenberg
For the first time, researchers can determine the amount of damage electric vehicle (EV) batteries can sustain before becoming a fire risk, thanks to research led by Elham Sahraei, associate professor of mechanical engineering at Temple University’s College of Engineering and director of both the Electric Vehicle Safety Lab and the Center for Battery Safety at Temple.
“We have been working for many years to come up with a criteria that can predict a short circuit in lithium-ion batteries when they are subjected to mechanical impact,” explained Sahraei.
Called the SAHRAEI failure criteria, the major breakthrough also estimates the probability of an EV battery failure rather than providing a simple pass-or-fail result.
“Instead of saying, ‘Yes or no, a battery is going to fail,’ we have now created a model that allows us to predict a probability of failure,” she said. “This means you can compare two scenarios together.”
For more than a decade, Sahraei has been working on the tool that looks at the way batteries deform upon impact.
EV battery packs are unique in that crashes could lead to a short circuit and, in extreme cases, cause a fire and thermal runaway. As a result, heavy protective structures, adding ‘dead mass’—sometimes hundreds of extra pounds—are used around EV battery packs to prevent deformation during a crash. However, Sahraei said creating a universal failure model for battery short circuits can enable better prediction of safety concerns and therefore allowing reduction of this dead mass.
“The traditional approach was that you make the structure around the battery so stiff that it will have zero deformation, because you didn’t know if even 1 millimeter of deformation is safe or not safe,” she said. “Now, with the SAHRAEI failure criteria, you can design structures that can absorb energy by controlled deformation while maintaining safety. This ultimately improves energy density at system level, which can increase the vehicle range."
As gas prices continue to climb and more consumers consider turning towards EVs, the criteria is now being used to help make lighter battery packs. By keeping it in mind when building battery structures, engineers can now remove some dead mass, making the structures smaller, and ultimately, creating more efficient EVs, according to Sahraei. In other words, battery structures do not need to be ‘overbuilt.’
“Not every dent is a disaster,” said Sahraei. “The biggest misconception is that any deformation will cause failure and short circuit and fire and explosion. This is not correct.”
“We make all these new developments available for stakeholders through the Center for Battery Safety. Our annual workshop is scheduled for December 4 at Temple (register here). We also work directly with EV manufacturers to develop and calibrate battery and short circuit models to use for optimizing their designs. Beyond our academic research, we have started a company, Inovele LLC, providing this technology to companies interested in implementation of our work into their products.
Earlier this year, Sahraei received the 2025 SAE International Award for Safety in Transportation Honoring Arnold W. Siegel. The award recognizes those making an impact on transportation safety. Last year, Sahraei and Marian Bula, collaborator from Altair (Part of Siemens now), won the ASME Edward F. Obert Award for an outstanding paper.
The criteria can also be used when building other devices that have lithium-ion batteries, such as phones, tablets and computers, she said.
“This is the result of a lot of hard work of my students,” Sahraei said, also thanking her department, college, university, industry partners and the Office of Naval Research for “continuous support that has enabled us to continue digging in this research area.”
