The sky-high lawsuit worth 2.3 billion yuan has not deterred car manufacturers from making their own battery packs.
On December 25th of last year, a claim lawsuit worth 2.3 billion yuan brought a major quality dispute in the domestic power battery industry to the forefront.
According to an announcement released by Sunwoda, Sunwoda Electric Vehicle Battery Co., Ltd., a subsidiary of Sunwoda responsible for power battery business, was sued by WeRui, a power battery subsidiary of Geely Group. The reason for the lawsuit is that from June 2021 to December 2023, the battery cells delivered by Sunwoda Electric Vehicle Battery Co., Ltd. to WeRui Power had quality problems. Based on this, WeRui claimed 2.3 billion yuan in compensation from Sunwoda Electric Vehicle Battery Co., Ltd.
A user notice issued by Zeekr in 2024 showed that a large number of Zeekr 001 WE86 models delivered between 2021 and 2023 had problems such as slower charging and abnormal battery degradation.
The battery packs installed in the Zeekr 001 WE86 models have battery cells - the core components - purchased from Sunwoda, while the PACK and BMS of the batteries are self - developed by WeRui.
The Zeekr 001 is the first model of the Zeekr brand. It is built on the SEA vast architecture under Zeekr and is positioned in the pure - electric coupe market, with a starting price of over 2.5 million yuan. This car was first launched in 2021 and has undergone several facelifts since then. The battery cells used in the 2021 - 2023 Zeekr 001 models were from CATL and Sunwoda respectively. The model equipped with Sunwoda battery cells is the Zeekr 001 WE86.
After discovering the problems, in October 2024, Zeekr, under the guise of a "Winter Care Campaign", replaced the battery packs for free for the owners of the 2021 - 2023 Zeekr 001 WE86 models. Moreover, in the 2024 and 2025 Zeekr 001 models, Sunwoda battery cells were completely phased out.
WeRui believes that problems such as slower charging and battery pack degradation are due to the fact that the technology and materials of the battery cells delivered by Sunwoda do not meet the previously signed technical agreement. Therefore, the cost of replacing the battery packs and the loss of the Zeekr brand image should be borne by Sunwoda. So it claimed 2.3 billion yuan in compensation from Sunwoda.
However, Sunwoda pointed out that WeRui's overly aggressive charging strategy and the "battery locking" operation, which changed the battery usage conditions, are the root causes of the problems. In addition, Sunwoda once said in a media interview: "We have conducted a large number of tests on the same type of battery cells. Currently, the battery pack systems we independently designed and provided to other customers have not shown any quality problems."
A compensation of 2.3 billion yuan would undoubtedly be a heavy blow to Sunwoda. According to Sunwoda's Hong Kong stock prospectus, from 2022 to the first quarter of 2025, Sunwoda's net profit attributable to the parent company was 1.068 billion, 1.076 billion, 1.468 billion, and 0.386 billion yuan respectively. This means that if WeRui wins the lawsuit, Sunwoda will lose approximately two years' worth of net profit attributable to the parent company.
The damage to the corporate image among C - end users, which in turn affects the development of subsequent customers, is another shadow cast on Sunwoda Electric Vehicle Battery Co., Ltd. by this case. A Sunwoda insider told 36Kr: "The current situation is very unfavorable for Sunwoda, and many customers are waiting and watching."
For the entire automotive industry, this dispute reveals the hidden concerns of automobile manufacturers in mastering the autonomy of core components by self - manufacturing battery packs.
In recent years, in order to reduce their dependence on leading power battery companies and gain more pricing and customization power, automobile manufacturers such as Leapmotor, Li Auto, and Xiaomi have all self - developed PACK and BMS and purchased battery cells from battery manufacturers. However, the lawsuit between Sunwoda Electric Vehicle Battery Co., Ltd. and WeRui has now put one of the major hidden dangers of this model in front of many automobile manufacturers.
Difficult - to - control Battery Cell Quality and Sharp R - corners
The core point of contention in the dispute between Sunwoda Electric Vehicle Battery Co., Ltd. and WeRui is which, the battery cells or the BMS, should take the main responsibility for the quality problems of the battery packs.
In a battery pack, the battery cells are the most core components, which largely determine the battery pack's power level, the vehicle's range, etc.; the BMS largely determines how the battery cells are used. It is like the brain of the battery pack. Both can affect the performance of the battery pack.
According to Sunwoda's public statement, the same type of battery cells in the Zeekr 001 WE86 model + the battery pack system independently designed by Sunwoda "have not shown any quality problems when provided to other customers". This is not sufficient evidence to determine the responsibility of WeRui's BMS.
A battery engineer told 36Kr that generally speaking, "the same type of battery cells" means that the design scheme of the battery cell products supplied by Sunwoda Electric Vehicle Battery Co., Ltd. to other customers is the same as that of the battery cells installed in the Zeekr 001 WE86 model, but they may not be from the same batch.
There are likely to be differences in technology, materials, etc. between different batches of battery cells. "Even if the technology and materials are the same, there are still differences between different batches of battery cells; even if the materials are produced by the same material factory but from different batches, there will still be certain differences between the materials."
This is related to the control of production consistency by power battery manufacturers and their material suppliers.
"After years of development in the industry, the equipment used by everyone is basically the same, and the test indicators used are those more than 400 items." As the power battery technology route is gradually converging, "now the competition among battery manufacturers increasingly emphasizes manufacturing consistency, but it is not easy to achieve."
A battery cell engineer told 36Kr a common case:
"During the production process, there may be some metal debris on the production line. These debris are very small and may not be detected.
After they enter the battery cells, there may be no problems in the short term. However, during the charging and discharging process of the battery cells, they will expand and contract due to the breathing effect. At this time, the metal particles are likely to continuously rub against the separator as the battery cells expand and contract, and eventually pierce the separator, causing the positive and negative electrodes to come into direct contact, resulting in a micro - short circuit in the battery cell.
After a micro - short circuit, the battery cell will release less power than a normal battery cell, and the voltage will change more rapidly. As a result, the cycle life of the entire battery pack will be affected.
According to the barrel effect, even if only one battery cell in the battery pack has a problem, the discharge capacity of the entire battery pack will decrease."
In addition, all the battery cells installed in the Zeekr 001 WE86 model use the winding process. Therefore, some battery industry insiders have provided such an analysis idea: "In the early stage, the industry had insufficient experience in the design and control of the winding process, so the R - corner is also likely to be a major factor causing quality problems."
The so - called R - corner "is like the arc angle at the connection between the straight and curved parts of a school sports field track". During the winding process, if this angle is folded into a sharp right - angle or even an acute angle, over time, the separator will be pierced by this angle, causing a short circuit in the battery cell.
"It is not difficult to identify the problems of the battery cells." PACK manufacturers can first only replace the battery cells for preliminary identification. Then, through CT scanning, disassembly analysis, mirror analysis, material analysis, R - corner analysis, etc. of the battery cells, they can finally identify the battery cells with the same problem characteristics.
"PACK manufacturers need to understand the more than 100 design indicators of the battery cells, list all these indicators, and test them one by one. Eventually, all problems can be detected. Even if they are not detected during the R & D stage, they can be detected after mass production on the large - scale production line."
Extreme BMS Strategy + Slightly Defective Battery Cells May Not Necessarily Cause Malfunctions
However, Sunwoda's statement about the BMS is not entirely unfounded. The BMS in a battery pack is a system composed of hardware such as BCU and software algorithms. Whether this "brain" of the battery pack is smart or not is indeed related to the performance of the battery pack.
An engineer with many years of BMS R & D experience described a possible scenario to 36Kr -
Electric vehicles can automatically recover energy or have coasting energy regeneration. When the accelerator pedal of the vehicle is released, the kinetic energy will be converted into potential energy, "which is equivalent to the battery starting to charge".
"According to the characteristics of lithium batteries, when the ambient temperature is 25 degrees Celsius, the energy recovery ability of the battery pack is the strongest, and it can accept any amount of power input.
However, if the temperature is too low, such as at minus 5 degrees Celsius, the battery pack may only be able to accept a feedback current of 50 amperes. At this time, if a current of 55 amperes or even 60 amperes is input into the battery pack, according to the characteristics of lithium batteries, lithium precipitation is likely to occur in the battery cells."
Then the BMS starts to play a role.
"It will protect the battery pack. If the feedback current to the battery pack is too large, the fault light on the vehicle will light up. If the current is even larger, the BMS will directly cut off the high - voltage power. However, if the BMS algorithm is always on the verge of cutting off the high - voltage power and reporting a fault, that is, it is constantly testing the limit of the battery cells' capabilities." Over time, the battery cells are more likely to degrade, and problems such as increased voltage difference may occur.
This BMS engineer explained that this situation may involve both the BMS and the motor.
"On the one hand, it may be that the BMS strategy is not well - designed; on the other hand, it may also be a problem of control accuracy. For example, the motors of United Automotive Electronic Systems and Inovance have high control accuracy. At minus 5 degrees Celsius, they may allow a maximum current of 51 amperes to enter the battery pack. 51 amperes is 2% higher than 50 amperes.
2% is the limit in the control strategies of many BMS systems in the industry. Of course, there are also some that can reach 5%.
If the accuracy of some motors is not high enough, and considering that any software, including BMS software, inevitably has a certain lag, the current entering the battery pack cannot be well - controlled, and the battery pack will be damaged."
If the BMS discharge strategy exceeds the limit of the battery cells' capabilities, it may also cause abnormal degradation of the battery pack.
The Zeekr 001 is a sports - style product. In order to obtain a more powerful driving experience, the owner may step on the accelerator pedal all the way down. At this time, the discharge capacity of the battery cells may exceed their limit.
"If Sunwoda's battery cells only have the ability to discharge 280 kilowatts, but the BMS algorithm forces them to discharge 300 kilowatts of power instantaneously, the battery cells will also be damaged."
This BMS engineer told 36Kr that this was not an uncommon situation in the early days of the industry because the application of batteries was limited, and enterprises had insufficient data on battery performance.
According to the characteristics of lithium batteries, during high - rate charging and discharging, the battery cells will generate tension, which means that the battery cells are prone to deformation. As a result, various problems such as reduced range may occur. "This is like a dance student with poor flexibility being suddenly pressed by the teacher. At that moment, her muscles are already strained."
"Conversely, if WeRui designs the BMS strategy extremely well, even if the battery cells have slight defects, the battery pack may not necessarily have problems. Just like an egg, if it is handled gently, it may not break."
However, battery manufacturers often have difficulty obtaining the BMS strategy documents of PACK manufacturers. To attribute the fault to the BMS strategy, battery manufacturers can lock a vehicle, "that is, prevent the vehicle from undergoing OTA updates". For vehicles that have already undergone OTA updates, they can also try to roll back through the Ministry of Industry and Information Technology's record - keeping system.
"Then, continuously conduct tests to reproduce the battery pack data under various working conditions, such as how much power is discharged when the accelerator pedal is fully pressed and how much when it is gently pressed, so as to decipher the PACK manufacturer's BMS strategy."
Difficulties in Determining Responsibility Cannot Stop Automobile Manufacturers from Self - manufacturing Battery Packs
The cooperation between WeRui and Sunwoda Electric Vehicle Battery Co., Ltd. is an epitome of the trend of automobile manufacturers self - manufacturing battery packs.
The extreme involution in the industry places higher requirements on automobile manufacturers' supply - chain cost control capabilities than ever before. As a key component of a vehicle, even today when the price of lithium ore has stabilized, the procurement cost of power batteries still accounts for about 30% of the total vehicle cost.
However, in the face of relatively powerful leading enterprises, automobile manufacturers often have difficulty obtaining price concessions. Therefore, a number of automobile manufacturers have successively embarked on the path of purchasing battery cells externally and self - manufacturing battery packs.
For example, Leapmotor purchases platform - based battery cells from several battery manufacturers such as CATL, Guoxuan High - tech, and Zenl Energy, greatly reducing its dependence on a single supplier; Xiaomi not only purchases complete battery packs from CATL but also purchases lithium iron phosphate battery cells from BYD's Fudi Battery; Li Auto jointly established a subsidiary with Sunwoda last year, purchases battery cells from Sunwoda, and self - develops Li Auto brand batteries.
Self - manufacturing battery packs helps automobile manufacturers reduce costs. In addition, automobile manufacturers' in - depth and comprehensive participation in the design and production of battery packs is more conducive to their control of product quality; at the same time, it also means that automobile manufacturers have grasped the product customization power.
However, the dispute between WeRui and Sunwoda also shows the industry the "mine" in this model - once there are quality problems with the battery packs, the division of responsibility will inevitably be a tortuous process.
Even with the strategy of purchasing platform - based battery cells from different battery manufacturers, "there is still a possibility of mutual blame when problems occur".
Purchasing platform - based battery cells and self - manufacturing battery packs seem to control the variable of the battery pack. However, a battery engineer told 36Kr: "The characteristics of battery cells from each battery factory are different. To make them achieve the same performance, automobile manufacturers still need to adapt different BMS strategies and thermal management strategies for them."
Platform - based battery cells mean a high degree of standardization in size, interface, structure, etc. However, due to differences in material systems such as the electrolyte formula and the surface treatment of negative electrode materials of different manufacturers, combined with the chemical characteristics of the battery cells themselves, the battery cells produced by different manufacturers have their own characteristics. "Just as the saying goes, there are no two identical leaves in the world."
Although these battery cells have all passed the tests of the same automobile manufacturer, when formulating test standards, automobile manufacturers usually set a range rather than a specific value. As long as the battery cells are within this range, the automobile manufacturer will approve their use in vehicles. Therefore, there will be certain differences in the performance parameters of the battery cells of each battery manufacturer.
"Then the BMS and thermal management strategies of automobile manufacturers may be stricter for the battery cells of one manufacturer and looser for those of another." Otherwise, "there may be situations where, for example, in the same battery pack produced by an automobile manufacturer, the vehicle's range is different when using the same - capacity battery cells from Sunwoda and CATL."
"For example, some battery cells with good quality control have lower internal resistance than others, so they generate less heat. Therefore, automobile manufacturers can be more lenient in thermal management.
For instance, when charging battery cells with good quality control and those with poor quality control using a DC fast - charging gun at the same time, for the battery cells with good quality control, cooling can be started when the battery pack temperature reaches 32 degrees Celsius. After charging, the battery pack temperature may be 35 degrees Celsius.
However, for battery cells with poor quality control, cooling may need to be started when the battery temperature reaches 31 degrees Celsius. Otherwise, after being fully charged, the battery pack temperature