[Fact Check] Five Key Issues in the Clash Between Public and Private Sectors Over 'Overcharging'

Controversy Grows After Seoul's Charging Rate Limit Measures

Controversy surrounding the proposed overcharging restriction measure as part of electric vehicle fire prevention efforts continues unabated. This is because Seoul City is pushing for a plan to prohibit parking in lots based on charging rates, despite the fire causes not being identified. Electric vehicle owners, automakers, and the government have expressed negative views on this. The key issues have been summarized.

An electric vehicle that was brought into a Mercedes-Benz Korea authorized service center in Seoul is parked on the 14th, when the free inspection of electric vehicles began.
[Photo by Yonhap News]

Does overcharging increase fire risk?

Seoul City cited "excessive charging close to full charge" as one of the main causes of electric vehicle fires. While acknowledging that there is controversy over limiting the charging rate, they judged that at this point, imposing limits is a meaningful way to prevent fires. This is the background for the plan to allow only electric vehicles with a 90% charging limit to enter underground apartment parking lots.

Automakers consider the term "overcharging" itself to be incorrect. Since battery cell manufacturers initially leave about a 20% safety margin (buffer space), and an additional 3-5% is set during the battery pack or vehicle assembly process, the "100% full charge" displayed on vehicle navigation systems actually uses less than 80% of the battery capacity. Moreover, balancing control operations are performed to prevent performance degradation caused by voltage differences among numerous battery cells. Since the cell with the smallest remaining capacity is used as the reference during this process, the margin increases further.

Hyundai Motor recently explained in reference materials that "battery fires mostly occur when manufacturing defects or external impacts cause internal physical short circuits, resulting in high current flow and heat generation, which then leads to ignition due to oxygen or flammable byproducts produced by the decomposition of chemical substances."

Is there any chance the battery could be charged beyond its capacity due to problems?

Overcharge prevention technologies have been established in several stages. Apart from the safety margin, the charger controller regulates current, while the Battery Management System (BMS) monitors the charging status in real time. The BMS acts as the battery's brain, providing information on charge amount, degradation (health) status, voltage deviation, insulation resistance, temperature, overvoltage, undervoltage, and more.

Recently, BMS capable of detecting momentary or micro short circuits, which are considered fire causes, have been developed. Even if the BMS malfunctions or encounters problems, a separate physical safety circuit operates to forcibly cut off the switch that allows current flow.

Minister of the Interior and Safety Lee Sang-min is inspecting the site of an electric vehicle fire in the underground parking lot of an apartment complex in Cheongna, Seo-gu, Incheon, on the morning of the 14th.
[Photo by Yonhap News]

Does the fact that electric vehicle companies recommend charging below a certain level mean they acknowledge full charging is dangerous?

Some electric vehicle manufacturers have implemented functions that allow owners to limit the battery charge rate below a certain threshold. These functions were publicized recently due to increased anxiety following fire incidents, leading some to argue that this acknowledges a direct link between charging rate and fire risk.

In response, a Hyundai Motor official stated, "This function is a recommendation to use the battery more efficiently over a longer period rather than a fire prevention measure." They clarified that it reflects the negative impact of frequent rapid or slow charging on battery durability and is unrelated to fire incidents. While charging rate may affect fire scale or duration, it is clearly unrelated to ignition.

Then why do electric vehicle fires occur?

It is difficult to identify fire causes because many vehicles are completely burned. However, a past investigation report on Kona electric vehicle manufacturing defects, which led to a large-scale recall, concluded that internal short circuits in battery cells were highly likely to cause fires. The investigation was conducted jointly by the Korea Transportation Safety Authority's Automotive Safety Research Institute, the automaker (Hyundai Motor), and LG Energy Solution (battery cell manufacturer).

Since then, there have been various fire cases under different circumstances, but the causes have not been identified. In some electric vehicles, fires started in areas unrelated to the battery. Hyundai Motor explained, "Generally, battery fires mostly occur when manufacturing defects or external impacts cause internal physical short circuits, or when high current flows between the positive and negative electrodes generating heat, leading to ignition due to oxygen and flammable byproducts produced by chemical decomposition."

At the No. 1 Public Parking Lot in Yeoksam Cultural Park, Gangnam-gu, Seoul, officials from Gangnam-gu Office, Gangnam Fire Station, Gangnam Urban Management Corporation, and GuardK, a company manufacturing lithium battery fire response products, are conducting a simulated training for electric vehicle fire response.
[Photo by Yonhap News]

Can charging rate limits be enforced?

It is practically difficult for apartment resident representative meetings to block vehicles capable of charging beyond 90%. This is because it is hard to specifically identify battery charge rate as a fire cause, and it could lead to property rights infringement. Some apartments, after discussion, concluded that instead of blocking such vehicles from parking, they would recommend adding or inspecting fire prevention and suppression equipment. The court's previous invalidation of parking restrictions on certain vehicle types has also been brought up again.

The government, which is reviewing joint measures, is also negative. On the 21st, Park Sang-woo, Minister of Land, Infrastructure and Transport, stated at the National Assembly Land, Infrastructure and Transport Committee plenary session, "We will actively participate in discussions to ensure local governments do not act independently and will jointly determine necessary measures." Regarding the causal relationship between charging rate and fires, he said, "It has not been proven. Experts have differing opinions, so it is difficult to confirm."

This content was produced with the assistance of AI translation services.