Geely Auto is mounting an unnamed technical challenge against rival BYD, taking direct aim at potential safety risks of excessive battery temperatures caused by the latter’s heavily promoted flash charging technology.
Geely published a post on its official WeChat account on Tuesday with a blunt headline that translated as — “Temperature above 65°C? Not recommended!”
The article cited China’s current national standard GB/T44500-2024, noting that the reference threshold for the maximum charging temperature of lithium iron phosphate (LFP) power batteries should not exceed 65°C.
Geely did not name any competitor in the article. But this is widely seen as an implicit jab at BYD, which is aggressively promoting its second-generation Blade Battery and 1,500-kilowatt flash-charging technology.
Geely’s core argument is built on physics. The company cited Joule’s law, saying that battery heat generation rises exponentially as current increases. The faster the charging speed, the faster the cell temperature climbs.
As megawatt-level fast charging becomes increasingly common, battery thermal management faces higher technical requirements, Geely said.
The company said its Shendun Golden Battery, tested by the China Automotive Technology & Research Center, recorded a peak temperature of just 64°C throughout the full megawatt-level charging process.
Geely also emphasized that its battery passed the full GB38031-2025 certification last May, a standard dubbed the “strictest battery safety order in history.”
“Charging fast is not enough; what matters more is ensuring safety!” Geely wrote in the post.
The trigger for the controversy can be traced back to last month. On May 6, a Chinese battery industry blogger livestreamed a test of BYD’s flash-charging model, the Fang Cheng Bao Tai 3.
The test showed that under an ambient temperature of 25°C, the model charged from 9% to 97% in 9 minutes and 9 seconds. But temperatures at multiple test points exceeded 74°C, peaking at 76.42°C.
The blogger noted that battery charging temperatures are generally around 60°C, and exceeding 70°C is basically not permitted. He warned that excessively high temperatures could cause electrolyte gassing and trigger the risk of SEI film decomposition.
BYD initially issued a brief response. Li Yunfei, general manager of its branding and public relations division, said on social media platform Weibo on May 7 that everyone is welcome to visit the Flaming Mountains in Turpan, Xinjiang during the hottest months of July and August, and try out flash charging while there.
But the controversy did not subside. Other battery makers also joined the discussion. An executive at Gotion High-tech (SZSE: 002074) said at an industry conference on May 17 that ultra-fast charging does indeed affect battery life.
The executive said the safe operating temperature for LFP batteries is 60°C. Lithium hexafluorophosphate begins to slowly decompose at 60°C and accelerates its decomposition at 70°C. Lithium hexafluorophosphate accounts for more than 60% of electrolyte costs and is the key material for lithium-ion conduction.
Facing persistent questioning, BYD eventually hit back directly. Sun Huajun, chief technology officer of the company’s battery business group, refuted the claim that flash charging damages batteries during an interview with Chinese media on May 19.
“You can’t simply say flash charging damages batteries,” Sun said. He pointed out that from 1C and 2C to 4C and 5C, every increase in charging rate prompted questions about battery damage, but technology has advanced each time.
Sun said the symmetrical structure of BYD’s Blade Battery allows current to flow out from both ends, with both the top and bottom surfaces dissipating heat simultaneously, resulting in relatively lower thermal resistance. BYD also optimized the dimensions of the second-generation Blade Battery to accommodate flash charging.
On the question of whether 70°C is the battery’s limit, Sun said no. He noted that just a few years ago, the industry still believed the high-temperature ceiling for LFP batteries was 60°C.
“We should not be bound by static numbers,” Sun said. He stressed that the core lies in understanding the mechanism by which temperature affects battery life, and then continually pushing boundaries through innovation.
The backdrop to this debate is the intense market rivalry between Geely and BYD. According to data from the China Passenger Car Association (CPCA), Geely topped the automaker retail sales ranking for the first five months of 2026 with 848,116 units, though down 17.7% year-on-year. BYD followed with 766,401 units, down 39.1% year-on-year.
In the new energy vehicle (NEV) segment, BYD remained in first place, while Geely ranked second with 470,396 units.
BYD has stopped producing pure fuel-powered vehicles since March 2022, focusing on NEV models, including battery electric vehicle (BEV) and plug-in hybrid electric vehicle (PHEV) models. Geely still maintains a lineup of fuel-powered cars.
This article was first published by Phate Zhang on CnEVPost, a website focusing on new energy vehicle news from China.
