EV fire risk from overcharging exaggerated: Expert

Electric vehicle fires do not occur due to the depth of charge (amount of charge), but rather due to internal failures within the battery cells or defects in the battery management system (BMS), according to a leading battery expert and professor from Sungkyunkwan University in South Korea.

“Overcharging is not the decisive cause of EV fires,” Professor Yoon Won-sub, a leading battery expert from Sungkyunkwan University‘s Department of Energy Science, said in an interview with Korean media on Friday.

“The most reasonable explanation for the recent Mercedes-Benz EV fire is a defect within the battery cell,” he added, while asserting that there is little correlation between overcharging and battery fire incidents.

His remarks come in response to public concerns about a possible link between overcharging and the recent EV fire in Cheongna, Incheon.

“It is a common misconception among the general public that charging to 100 percent is dangerous,” Yoon said. “While the depth of charge is related to fire risk, it is not the dominant cause.”

He elaborated that the full capacity of a nickel-cobalt-manganese (NCM) battery cathode is 275 mAh per gram, but only about 200 to 210 mAh is used in practice.

“When we refer to 100 percent charge, this includes a safety margin,“ Yoon said, explaining that both battery manufacturers and automakers have equipped their systems with BMS and physical control (power cutoff) mechanisms to prevent overcharging.

Regarding the Cheongna incident, Yoon pointed to the possibility of a defect in the battery cells as the probable cause. He viewed the recent trend among automakers to disclose information about battery manufacturers as a positive sign while raising the need for the composition and ratio of cathode materials to be made public as well. He also highlighted the importance of the BMS in preventing accidents.