Geely Challenges BYD Flash Charging Safety as Battery Temperature Debate Intensifies

The competition between Geely and BYD has expanded beyond sales performance into a technical debate centered on battery charging safety. The discussion intensified after Geely publicly cautioned against battery cell temperatures exceeding 65°C during charging, a statement widely interpreted as criticism of BYD's flash-charging technology. As automakers race to deliver faster charging experiences, the industry is increasingly focused on balancing convenience with battery durability, thermal stability, and long-term reliability for electric vehicles.

Geely issued the statement through its official WeChat account, publishing an article with a headline that translated to "Temperature above 65°C? Not recommended!" The company referenced China's national standard GB/T44500-2024, which indicates that the recommended maximum charging temperature for lithium iron phosphate batteries should remain below 65°C. Although Geely avoided directly naming competitors, industry observers widely viewed the message as a response to BYD's second-generation Blade Battery and its 1,500-kilowatt flash-charging system.

Physics and Thermal Management at the Center of the Debate

Geely based its argument on established physical principles, particularly Joule's law, stating that heat generation rises rapidly as charging current increases. According to the company, faster charging rates inevitably lead to higher battery temperatures, making battery thermal management increasingly important as megawatt-level charging becomes more common. Geely emphasized that advanced cooling systems and precise thermal controls are becoming essential requirements for future electric vehicle architectures.

The company highlighted performance data from its Shendun Golden Battery, which was tested by the China Automotive Technology & Research Center. Geely stated that during full megawatt-level charging, the battery reached a peak temperature of only 64°C. The company also noted that its battery passed GB38031-2025 certification last year, a regulation often described as one of the strictest battery safety standards ever introduced. Geely concluded its statement by asserting that charging speed alone is insufficient without strong safety protections.

Battery Test Results Spark Industry-Wide Discussion

The controversy gained momentum after a battery industry blogger livestreamed a charging test on May 6 involving BYD's Fang Cheng Bao Tai 3 model. Under an ambient temperature of 25°C, the vehicle reportedly charged from 9 percent to 97 percent in 9 minutes and 9 seconds. However, several temperature measurements exceeded 74°C, with the highest reading reaching 76.42°C, triggering concerns among industry observers regarding battery charging safety.

The blogger argued that battery charging temperatures typically remain around 60°C and suggested that exceeding 70°C is generally discouraged. He warned that elevated temperatures may lead to electrolyte gassing and possible decomposition of the solid electrolyte interphase layer. These effects could potentially influence battery longevity and stability under extreme operating conditions, although the precise impact depends heavily on cell design, chemistry, and thermal management strategies.

Battery Manufacturers Respond to Safety Concerns

BYD initially responded through social media. Li Yunfei, the company's branding and public relations chief, invited users to test flash charging in the hot summer conditions of Turpan in China. Nevertheless, public discussion continued, with additional battery manufacturers weighing in on the topic of high-temperature charging and battery degradation.

An executive from Gotion High-tech stated during an industry conference on May 17 that ultra-fast charging can affect battery life. The executive noted that the safe operating temperature for LFP batteries is around 60°C and explained that lithium hexafluorophosphate begins gradual decomposition at 60°C while degradation accelerates near 70°C. Since this material is crucial for lithium-ion transport and represents a large share of electrolyte costs, its stability remains a critical factor for battery performance.

BYD Defends Flash Charging Technology

Facing ongoing criticism, BYD responded more directly through comments from Sun Huajun, chief technology officer of its battery business group. During an interview with Chinese media on May 19, Sun rejected the idea that flash charging inherently damages batteries. He argued that every increase in charging rates, from 1C and 2C to 4C and 5C, has historically raised similar concerns, yet technological improvements have consistently addressed those challenges.

Sun explained that the symmetrical design of the Blade Battery allows electrical current to flow from both ends while enabling heat dissipation through multiple surfaces, reducing thermal resistance. He added that BYD redesigned the dimensions of its second-generation Blade Battery specifically to support flash charging. Regarding temperature limits, Sun stated that previous industry assumptions have evolved over time and emphasized that innovation should continue expanding operational boundaries while understanding the mechanisms that influence battery aging.

Geely and BYD Rivalry Extends Beyond Technology

The battery charging safety debate is unfolding against a backdrop of intense competition in the electric vehicle market. Data from the China Passenger Car Association showed that Geely led automaker retail sales during the first five months of 2026 with 848,116 units, though sales declined 17.7 percent year over year. BYD ranked second with 766,401 units, reflecting a larger year-on-year decline of 39.1 percent.

Within the new energy vehicle segment, BYD retained the leading position while Geely ranked second with 470,396 units sold. BYD has focused exclusively on battery electric and plug-in hybrid vehicles since discontinuing pure internal combustion vehicle production in 2022. Geely, meanwhile, continues to maintain both conventional fuel-powered and electrified vehicle portfolios. As charging technologies advance, the debate over performance, durability, and safety is expected to remain a defining issue for the global EV industry.

Frequently Asked Questions

Why is the 65°C battery temperature threshold important?
The 65°C threshold is widely referenced because higher temperatures may accelerate chemical degradation inside lithium iron phosphate batteries. Elevated temperatures can impact electrolyte stability, reduce battery lifespan, and increase safety risks under extreme conditions. Industry standards such as GB/T44500-2024 use this benchmark as a reference point for safe charging practices. However, some manufacturers argue that advanced battery designs and improved thermal management systems can safely operate beyond traditional limits while maintaining long-term reliability.

Why are Geely and BYD debating flash charging technology?
Geely and BYD are competing to deliver faster charging while maintaining battery safety and durability. Geely emphasizes strict temperature control and compliance with safety standards, whereas BYD argues that technological innovation allows batteries to safely handle higher charging rates. The debate reflects broader industry challenges as automakers pursue ultra-fast charging solutions. Ultimately, manufacturers must balance customer demand for rapid charging with thermal management, battery longevity, and evolving regulatory requirements.