Researchers at Graz University of Technology have discovered that the safety of electric vehicle batteries increases as they get older.
New studies conducted at Graz University of Technology (TU Graz) indicate that electric vehicle batteries are less dangerous as they age. The team now intend to define parameters for the subsequent use of discarded batteries.
As part of a project called ‘SafeBattery,’ the researchers have been studying the performance of lithium-based batteries in electric vehicles under crash loads for the past four years.
“The performance of new battery cells is largely known, so we dealt with the entire life cycle,” explained Christian Ellersdorfer, project manager at the Institute of Vehicle Safety.
Along with industry partners, the group has conducted research into scenarios that batteries may experience during their lifespan, such as vibrations and strong accelerations caused by parking bumps, serious accidents, and the constant charging and discharging of batteries.
Employing a range of techniques including crash tests, simulation models, and calculation methods, the researchers have concluded that vibrations and accelerations scarcely impact the behaviour of batteries.
However, constant charging and discharging of the battery results in more significant mechanical and electrical changes; battery cells aged in this way have a higher stiffness under mechanical load.
“But the changes don’t necessarily mean that batteries become more dangerous with age. On the contrary. The sum of the influences makes them safer over time because they also lose electrical energy,” said Ellersdorfer.
The team’s studies indicate that cells with decreased capacity content have a reduced course of thermal runaway in the case of internal short circuit. The reduced energy potential of older electric vehicle batteries reduces the potential of accidental battery fires, and thus their safety.
As a result of the group’s findings, manufacturers know what to expect from a battery cell, therefore facilitating material-saving designs and greater efficiency.
“Until now, the battery was installed in such a way that deformations could be ruled out in every conceivable scenario. Now manufacturers can make better use of the installation space. And safety checks on a new cell are valid for the life of the battery,” added Ellersdorfer.
