Illegal EV Battery Add-ons: Mixed Cells, No Cooling—A Dangerous Trend

Some merchants on platforms such as Douyin, Xiaohongshu, and Xianyu are offering aftermarket battery installation services for new energy vehicles (NEVs), claiming they can boost a vehicle’s original range—typically just over 100 kilometers—to around 300 kilometers. Prices for these services range from approximately RMB 7,700 to RMB 9,100. The installation process involves removing seats, disconnecting the original battery wiring harness, connecting an external battery pack, and securing it in the trunk or beneath the rear seats. These modifications typically lack professional battery management systems (BMS) and dedicated thermal management structures. Instead, the battery packs are often placed bare inside the vehicle’s enclosed cabin space, relying solely on passive cooling through their outer casing. While some service providers claim to use “brand-new, top-tier” battery cells, industry insiders reveal that most cells are actually sourced from traders, making it difficult to verify their origin and quality. There is a significant risk that these packs contain Grade B (second-hand) or even Grade C (scrapped) cells. According to Article 16 of China’s Road Traffic Safety Law, unauthorized alterations to a motor vehicle’s registered structure, construction, or characteristics are illegal. As the traction battery is a core component of NEVs, unauthorized modifications void the manufacturer’s warranty and may result in insurance claims being denied. In the event of an accident, vehicle owners could face primary legal liability. Currently, this sector operates without unified standards. Most installers lack proper qualifications for servicing new energy vehicles, and the battery packs themselves generally lack impact protection and thermal runaway prevention measures. Under conditions such as high temperatures or rough road vibrations, the risk of thermal runaway leading to spontaneous combustion or explosion rises significantly. As early-generation NEVs progressively exit their warranty periods, it is projected that by 2032, around 7.2 million vehicles nationwide will be out of warranty, fueling substantial demand for low-cost range-extending solutions—and further driving growth in this gray-market modification industry.