"Bomb" in the Trunk: Unauthorized Battery Modification of New Energy Vehicles Has Become a Gray Industry Chain
On some social platforms, advertisements for "installing additional batteries" in new energy vehicles are quietly spreading. Under the guise of "range extender packages" and "battery upgrades," merchants are peddling an alluring solution to car owners with range anxiety: parallelly connect an additional battery in the trunk or chassis, and the driving range will immediately increase by one or two hundred kilometers, all for just over ten thousand yuan.
"It's very simple. Just connect the original car battery and the additional battery in parallel. They operate independently and don't interfere with each other," an industry insider explained in a video posted on a social platform. For different car models, merchants offer two options: the "trunk version" and the "cargo box version." They promise "no impact on the warranty" and "non-destructive installation" on the original vehicle. Merchants have shared multiple cases: adding a range extender package to the Fangchengbao Leopard 5 to increase the driving range by 200 kilometers; adding 10 kWh of electricity to the Wuling Hongguang MINI with a 120-kilometer range; and upgrading the driving range of the Geely Xingyuan from 410 kilometers to 610 kilometers by installing an additional battery. For vehicles with severely degraded original batteries, these merchants can also provide the service of replacing the entire battery pack.
In the comment sections of such videos, car owners of various new energy brands have been asking whether their cars can have additional batteries installed. Merchants claim that they can carry out the operation nationwide. Industry insiders use short videos and social networks to attract customers online and then rely on offline modification workshops to carry out the actual installation. A hidden gray industrial chain of private battery modification is emerging.
According to Article 16 of the Road Traffic Safety Law of the People's Republic of China, no unit or individual is allowed to assemble motor vehicles or change the registered structure, construction, or characteristics of motor vehicles without permission. Modifying electric vehicle batteries, especially installing additional batteries or replacing batteries with a rated voltage that does not match the original vehicle's factory settings, is a clear violation of the law.
However, from another perspective, as the first batch of domestic new energy vehicles enters the high-incidence period of battery degradation, many car owners are more anxious about the driving range. Since replacing batteries through formal channels is expensive and inconvenient, private battery modification has become a dangerous but realistic solution.
Adventurous Modification
Some car owners are willing to take the risk of breaking the law to modify or install additional batteries, mainly due to their concerns about the vehicle's driving range.
"After the warranty period, the overall driving range drops to less than half. A car that could originally run 400 kilometers can only run 200 kilometers, and a car that could run 300 kilometers can only run a little over 100 kilometers," said Master Zhang, the person in charge of a ride-hailing operation company in East China, to Economic Observer. He said that in the face of this situation, some drivers will convert their operating vehicles for personal use and then purchase new cars. However, more drivers are reluctant to change their cars and can only go to small shops outside to "upgrade" the batteries.
Public data shows that the first batch of compliant new energy ride-hailing vehicles in China appeared in 2018, and it has been eight years since then. The first batch of large-scale ride-hailing and taxi vehicles are now crossing the "8-year or 120,000-kilometer" warranty threshold. These vehicles face two problems: either they have passed the warranty period for operating vehicles (some vehicle manufacturers do not provide warranties for operating vehicles), or their batteries have severely degraded due to high-intensity driving.
Most merchants on social platforms use the needs of ride-hailing drivers as an example. "Many drivers' cars have run over 300,000 kilometers, and the batteries have severely degraded, but the overall condition of the cars is still good. They are reluctant to invest too much in a new car, as running a ride-hailing service is not very profitable these days. By upgrading to a large Ningde single-cell battery here, spending 10,000 to 20,000 yuan can restore the driving range to that of a new car," a merchant introduced.
Besides ride-hailing drivers, many private car owners also want to increase their vehicle's driving range. Even if their vehicles are still within the warranty period, they are dissatisfied with the driving range, especially those entry-level electric vehicles with a range of only about 300 kilometers. Some hybrid vehicle owners hope to increase the pure-electric driving range to save on fuel costs. According to a merchant on a social platform, "The pure-electric driving range of many hybrid vehicles is very low. Car owners want to find a way to increase it so that they can save on fuel and make it more cost-effective."
For new energy vehicle owners, driving range is a "must-have," which is clearly reflected in the current market. In the past two years, more and more extended-range vehicles and hybrid vehicles with long pure-electric driving ranges (300 to 400 kilometers) and long-range electric vehicles (over 600 kilometers) have been launched, and the prices of these vehicles are more affordable. This has objectively led to a situation where earlier car buyers not only paid a high price but also did not get a longer driving range. They hope to get "compensation."
Merchants who modify batteries privately have seized the psychology of new energy vehicle owners who want to "achieve more with less money" and offered very attractive prices. According to the quotes of multiple merchants, the price of an additional battery pack is about 500 to 800 yuan per kWh. Installing a 20-kWh battery pack in a car costs about 15,000 yuan, and the driving range can directly increase by about 160 kilometers. The cost of replacing the entire battery is between 20,000 and 30,000 yuan.
In contrast, it is impossible for car owners to install additional batteries through formal repair channels, and the price of replacing a battery may double. According to the research results of the vehicle parts-to-whole ratio system index released by the China Insurance Automotive Technology Research Center, among the 59 pure-electric new energy vehicle models in its sample, the average single-piece parts-to-whole ratio of the power battery pack is as high as 50.96%. That is to say, for a 200,000-yuan new energy vehicle, the cost of replacing the power battery pack exceeds 100,000 yuan; for a 100,000-yuan vehicle, the cost of the battery pack is 50,000 yuan.
Master Zhang told Economic Observer that based on such cost considerations, almost no drivers choose to replace the battery at the official repair point.
What Are the Risks?
Privately installing or modifying vehicle batteries not only increases the driving range but also brings far more safety risks than expected.
"If the additional battery is an independent pack, there will be a problem of how the BMS (Battery Management System) of the additional battery can cooperate with the original BMS. If it is not an independent pack, then the problem is how to connect it to the original BMS. What is the reliability of the modified BMS? Especially in terms of thermal management, once it gets out of control, it may cause a fire accident," said Xu Jianzhong, the dean of the Beijing Huizhihuizhong Automotive Technology Research Institute.
Cao Xuejun, the vice president and chief engineer of Jingyou Technology, warned, "Many additional batteries are placed in the trunk. The trunk is prone to damage in rear-end collisions and other accidents. Once a collision occurs, it poses a great risk to the safety of the vehicle and the driver. There are matching and safety issues between the additional battery and the original BMS. Once the operation is improper, it is very dangerous. Car owners must think this through."
In fact, there have already been safety accidents caused by installing or modifying batteries. According to public reports, in November 2025, a new energy vehicle in Changzhou, Jiangsu, caught fire and was severely burned. The cause of the fire was a privately installed spare lithium battery for an electric bicycle carried in the car. The battery caught fire during driving and was not taken out in time, eventually igniting the vehicle.
Xu Jianzhong reminded that although installing and modifying batteries at third-party merchants seems cost-effective, there are many "traps" hidden in it. First, the source of the batteries is unknown. Multiple merchants claim that the battery packs for modification and installation are new batteries from CATL or EVE Energy. However, Xu Jianzhong believes that car owners need to confirm whether the merchants are authorized dealers of the battery companies. Even if they are authorized dealers, it cannot be ruled out that some merchants do not follow the rules and use Class B (defective products), Class C (inventory products), or even disassembled battery cells, allowing potentially dangerous battery cells to mix in.
Second, it is difficult to ensure the consistency of battery cells with different production dates, usage frequencies, and charge-discharge cycles when they are mixed together. Problems will reappear after a period of use. In other words, this method cannot completely solve the problem of range degradation. And if all the battery cells or modules are replaced as a whole, it is necessary to consider whether the cost is worth it compared with the remaining value of the original vehicle.
In addition, car owners will also face the risk of the warranty and insurance becoming invalid due to privately replacing the battery. "If you modify the three electric systems (battery, electric motor, and electronic control), the insurance company can completely refuse to pay compensation in case of an accident," Cao Xuejun clearly stated. For vehicles still within the warranty period, they will also lose the three-guarantee rights due to battery modification.
Contradictions to Be Resolved
According to relevant industry statistics, the number of out-of-warranty new energy vehicles reached 320,000 in 2025, is expected to reach 980,000 in 2028, and will rise to 7.2 million in 2032. As the number of out-of-warranty vehicles surges, many car owners are caught in a dilemma of "unable to afford to replace the battery and reluctant to sell the car." If they replace the battery through formal channels, they need to pay tens of thousands of yuan. At the same time, since the battery price is much higher than the vehicle's residual value, car owners are reluctant to sell their vehicles.
Cao Xuejun believes that this contradiction will be gradually alleviated over time. On the one hand, the prices of new energy vehicles are decreasing. The state still provides subsidies for new energy vehicle replacement and is promoting the cascade utilization of power batteries. It is economically feasible to replace an old car with a new one. On the other hand, the price of power batteries has dropped significantly compared with a few years ago. With the improvement of repair technology and the gradual popularization of repair outlets, the repair of power batteries will no longer be a high-difficulty and high-cost project.
Some power battery manufacturers have begun to launch battery repair services. For example, CATL launched the "Ningjia Service" brand in August 2024, providing services such as battery testing, maintenance, and recycling for new energy vehicle consumers, which can reduce the battery repair cost and break the situation of "only replace, not repair" in car dealerships.
"In fact, many car manufacturers' battery return-to-factory repairs are also completed by CATL," Cao Xuejun said. In the future, this form of specialized repair of the three electric systems by power battery manufacturers is expected to become the mainstream.
Different from the repair system of fuel vehicles, the repair system of new energy vehicles has not yet formed a virtuous cycle. Car owners going to small workshops to modify their vehicles privately is one aspect of this system, while the "monopoly" of repair resources by vehicle manufacturers is another aspect. In the past few years, the maintenance of new energy vehicles has been almost entirely in the hands of vehicle manufacturers. Third-party repair institutions are strictly restricted by vehicle manufacturers when trying to obtain vehicle repair manuals and technical data. There was a case where a third-party repair institution was sued for unauthorized battery repair. For various reasons, the involvement of third-party institutions in new energy vehicle repair has become a "forbidden zone."
The good news is that the policy has begun to address the repair dilemma of new energy vehicles. Since April 1 this year, the Interim Measures for the Recycling and Comprehensive Utilization of Waste Power Batteries of New Energy Vehicles have been officially implemented. The new regulations clearly require vehicle manufacturers to open up battery technical information to compliant third-party repair enterprises, promoting the standardization and transparency of the power battery repair market and significantly saving repair costs for new energy vehicle owners. As long as car owners choose to have their vehicles repaired at third-party repair institutions with formal qualifications and meeting the standards, the original "three electric systems" warranty remains valid.
In addition, the Inspection Regulations for the Operational Safety Performance of New Energy Vehicles, which came into effect in March 2025, included the three electric systems in the annual inspection for the first time, which will expose the risks of modified vehicles earlier. The National Standard for the Coding Rules of Lithium-ion Batteries, which came into effect in November 2025, assigns a unique identification code to each newly produced battery product, realizing the full-life cycle traceability of "one battery, one code," which will effectively prevent Class B, Class C, and disassembled battery cells from entering the circulation link.
After more than a decade of rapid growth, the new energy vehicle industry has now entered a peak period of vehicles going out of warranty and being retired. At this time, only by popularizing compliant, safe, convenient, and reasonably priced battery repair and replacement services can car owners avoid taking risks and putting a "bomb" in their trunks.
This article is from the WeChat official account "Economic Observer Automotive," written by Zhou Ju and reprinted with permission from 36Kr.