[Exclusive] Kona EV Fire Cause "Battery Internal Short Circuit"... Conclusion After 4 Years Still 'Presumed'

Fire Incidents of 1st Generation Kona EV Since 2019
'LG Energy Solution Responsibility ↑' Interpretation Ambiguous
Lithium Byproduct Generated by Folded Anode Tap Lead
Lithium Byproduct Growth Causes Short Circuit at Cathode Tap Lead
Cause 'Presumed' Through Fire Reproduction Test
Researcher "Difficult to Identify Specific Cause"

The cause of the Kona electric vehicle (EV) fires that have occurred since 2019 has been revealed. The Korea Automotive Technology Institute, which conducted the investigation, pointed to internal short circuits within the battery cells. This is interpreted to mean that the responsibility of LG Energy Solution, the battery manufacturer, is greater in fact.

The Korea Transportation Safety Authority's Automotive Safety Research Institute recently stated in the "Hyundai Kona Electric Vehicle Fire Occurrence During Parking Manufacturing Defect Investigation Report" that "the possibility of fire caused by internal short circuits in the high-voltage battery pack (BSA) battery cells has been confirmed."

1st Generation Kona EV

The institute disassembled and analyzed the recalled batteries to determine whether Hyundai Motor Company's recall measures were appropriate. The inside of a lithium-ion battery cell consists of an anode, cathode, a separator that physically blocks direct contact between the cathode and anode, and an electrolyte that acts as a medium allowing lithium ions to move to the electrodes. The tab leads attached to the cathode and anode connect the positive and negative plates to input and output electricity externally.

Lithium-ion battery installed in the 1st generation Kona EV [Photo by Korea Automobile Safety Research Institute report]

The institute viewed that the problem occurred as the anode tab lead was bent. This caused lithium byproducts to form, and a short circuit occurred inside the cell. Specifically, as the anode tab lead bent, lithium ions could not move to the anode. Lithium byproducts formed around the tab lead and grew with continued use. Due to the grown byproducts, a short circuit occurred at the cathode tab lead.

The process of lithium byproduct formation caused by the anode tab lead
[Photo by Korea Automobile Testing & Research Institute report excerpt]

Fire reproduction tests were also conducted. External factors such as thermal shock and vibration were judged not to be causes. Tests simulating fires caused by external short circuits of the battery were also performed but differed from the conditions of actual vehicle fires. Ultimately, based on the thermal runaway test (simulating fire caused by internal short circuits), the fire was 'presumed' to be caused by internal short circuits in the battery cells.

[Photo by Automobile Safety Research Institute, excerpted from the final report]

The Kona EV fires began on July 28, 2019, in Gangneung, Gangwon Province. The investigation found that there were 16 fire cases in South Korea. It was also revealed that a fire occurred in Jeju in April last year. There were 12 cases overseas as well. The most recent fire occurred in August last year in Canada.

Hyundai Motor Company conducted two rounds of public free repairs and recalls after the fires. In the first and second public free repairs and the first recall, the BMS (Battery Management System) logic was updated. In the second recall, the battery was replaced along with the update. The target vehicles were Kona EVs manufactured from May 11, 2018, to March 13, 2020 (25,083 units, including 1,314 Ioniq electric vehicles and 302 Elec City buses equipped with the same battery).

List of first-generation Kona EV fire incidents that occurred domestically [Photo by Korea Automobile Safety Research Institute report excerpt]

Hyundai stated that it has done its best along with the parts manufacturer (LG Energy Solution) to identify the cause of the fires and resolve the issues. To reduce the possibility of fire, the battery was improved and the BMS logic was updated. The battery includes cathode insulation coating to reduce the possibility of short circuits even if lithium byproducts occur, and even if there is a problem with the battery, the BMS enables preemptive response.

However, controversy is expected over this conclusion. The institute identified that the bending of the anode tab lead occurred during the battery cell manufacturing process, but it could not clarify why the byproducts cause short circuits. Regarding the use of the word 'presumed,' the institute responded, "It is difficult to specify the exact cause of fire occurrence (such as why internal short circuits happen)."