Cell to Chassis: The Key to Future Competitiveness of New Energy Vehicles
Author | One Racing Horse
CTC stands for Cell to Chassis, a process that directly integrates battery cells with vehicle chassis. It enhances the integration of the battery system with the powertrain system and chassis of electric vehicles, reduces the number of components, saves space, improves structural efficiency, significantly reduces vehicle weight, and increases battery range. CTC is regarded as a key core technology that will determine the success or failure of new energy vehicle competition in the next phase.
Three Phases of CTX
Battery cost accounts for more than one-third of the overall vehicle cost and is a crucial factor affecting the performance of the vehicle. Therefore, the integration of the battery system is an essential aspect of the reform of new energy vehicle production and manufacturing. The integration of the battery system has gone through several stages:
CTM: Cell to Module, originally, the industry hoped to standardize the battery cells to reduce costs through economies of scale. However, due to different requirements from OEM models, it is challenging to unify the battery size produced by battery manufacturers. Therefore, the standardization of battery systems turned to module integration. In recent years, the focus of battery system integration has been on continuously improving the standardized battery modules’ size, such as the typical 355, 390, and 590 module.
CTP: Cell to Pack, due to the existence of modules, the utilization rate of battery packs is relatively low. Therefore, Ningde times, BYD, Hive Energy, and other companies have successively released their respective CTP schemes, skipping the standardized module process and directly integrating battery cells into the battery pack, effectively improving the energy density and space utilization rate of the battery pack.
CTC: Cell to Chassis is not limited to a redesign of battery placement but also includes the integration of the electric drive and control systems. By integrating the battery, motor, electrical control, on-board charger, DC/DC, and chassis height, energy efficiency can be optimized and power allocation can be improved through an intelligent powertrain domain controller. This is the future trend, which requires automakers and battery suppliers to have multiple cross-domain abilities. Most vehicle manufacturers need to have the ability to design battery cells and highly integrate three-electric systems. Battery companies may need to layout the motor, chassis design, and other sectors. Currently, Tesla has announced its CTC plan, and Volvo, BYD, and Ningde times are accelerating their layout.
Tesla’s CTC Scheme and Integrated Casting Technology
In Tesla’s 2020 Battery Day speech, the CTC technology was inspired by the aviation industry, which fused the fuel tank with the wings instead of having a fuel tank in the wings. This new design effectively reduces the number of components and total weight of the battery pack, thereby increasing the efficiency of manufacturing and reducing costs to ultimately increase the range of electric vehicles. It is reported that Tesla’s latest third-generation cylindrical 4680 battery cells and the previous generation battery cells can use the CTC technology.
In June 2021, Tesla released a battery system patent named INTEGRATED ENERGY STORAGE SYSTEM, with the patent number US 2021/0159567 A1, which elaborated on the integration technology of the 4680 Structural Battery (CTC) system.
In October 2021, Tesla showcased the 4680 Structure Battery for the first time during a factory tour event held in Berlin. The overall design concept was consistent with the disclosed information from the patent.
Based on the patent and public information, Tesla’s CTC has the following characteristics:
- The battery pack cover is bonded with the battery cells and directly connected to vehicle structural components such as seats.
- Resin materials are used to fill the gaps between battery cells, providing both thermal protection and structural support.
- The previously used aluminum wire connections are replaced with Busbar connections, using busbar pins to connect the electrical components and the battery management system collection board directly.
- The battery pack is equipped with eight pressure relief valves on one side to enhance thermal management.
- The serpentine pipe arrangement between battery cells is parallel to the axle direction, reducing resistance by shortening the pipe length and improving cooling uniformity.
Tesla’s CTC solution reduces the number of support components, lightens the overall weight of the vehicle, and increases the battery capacity. This application lowers vehicle weight by 10%, increases range by 14%, reduces the number of components by 370, reduces unit costs by 7%, and reduces unit investment by 8%, which significantly improves the efficiency of automotive production.
In addition, when talking about Tesla’s CTC solution, one cannot ignore the Integrated Casting Technology. In 2020, during Tesla’s Battery Day, Tesla first used integrated casting technology on the structural components of the Model Y’s rear body. The front and rear body and chassis battery pack combine to form the vehicle body. Compared with traditional stamped and welded processes, Tesla’s integrated casting technology significantly reduces the number of vehicle body parts, lowers the complexity of the vehicle body, and realizes weight reduction. At the same time, the welding lines of the vehicle body and corresponding robots and workers are replaced by a single casting machine. The integrated vehicle body does not require secondary heat treatment, greatly increasing manufacturing efficiency (45 seconds to produce a vehicle body in the Berlin factory). Furthermore, the equipment used for integrated casting technology requires less floor space compared to traditional stamped and welded processes, saving 35% of floor space and simplifying the production process.
Additionally, Liangdao Auto launched the first domestically produced CTC solution.On April 25th, 2022, the CTC Battery Chassis Integration Technology Release Conference of the LINGPAI Intelligent Power took place. Unless unforeseen circumstances occur, LINGPAI C01, which will be launched in August this year, will become the first product with the CTC technology in China.
The idea of CTC in LINGPAI came from Zhu Jiangming. Inspired by the transition from detachable batteries in feature phones to integrated batteries in smartphones in 2016, he wondered, “Can we apply this idea to automotive power batteries?” He immediately started the pre-research and set up a battery R&D team, which gained the technical capabilities for manufacturing the whole battery module, battery pack, and BMS.
LINGPAI integrated the battery, chassis, and underbody design, which is an advanced technology that simplifies product design and production processes. By redesigning the battery-carrying tray, the entire bottom chassis structure is interlocked with the battery tray structure, thus innovating the installation process. By reducing redundant structural design, the number of parts can be effectively reduced, increasing space utilization and system-specific energy while making the body and battery structures complementary, significantly improving battery impact resistance and body torsional stiffness.
First, it increases battery capacity by reducing the module, producing more space for battery placement, and increasing the battery layout space by 14.5% compared to traditional solutions.
Secondly, it reduces the weight of the car by saving structural components through the cancellation of the battery module hierarchy, increasing the lightweight coefficient of the body compared to traditional solutions by 20%, while achieving better economic and performance balance.
Thirdly, it improves the vehicle’s torsional stiffness by 25%, making it more resistant to resonance, providing better NVH performance, handling, responsiveness, and driving performance, while improving passive safety.
Fourthly, through software control, the active safety of the battery is also improved. It is said that the technique of AI BMS is adopted to enable real-time monitoring, thus essentially eliminating safety issues resulting from battery or cell failure.
Moreover, strictly speaking, LINGPAI’s current technology is MTC (Module to Chassis) because it still retains the battery module – Module, which integrates the battery module into the chassis, rather than integrating the battery cells directly into the chassis. This solution compromises in the areas of CTC, such as saving space, improving integration, and reducing parts, but it is more convenient and cost-effective in terms of maintenance and repair and can be quickly launched into the market.
BYD’s CTB Battery-Chassis Integration Technology Meets on 520.In 2021, BYD launched a new pure electric exclusive platform, e3.0, which achieved “eight-in-one” power system integration by integrating eight major modules including the drive motor, motor controller, reducer, high-voltage distribution box, inverter, on-board charger, vehicle controller, and battery management system. The super-safe blade battery was continued to be used and further integrated the blade battery into the entire vehicle body, and deeply integrated the vehicle’s driving, braking, steering and other functions.
Recently, BYD announced that the Sea Lion will start pre-sales on May 20th and released the CTB battery body integration technology based on the platform 3.0. If the Dolphin is seven-in-one and the Yuan PLUS is eight-in-one, then the Sea Lion further integrates the battery into the vehicle body based on the eight-in-one platform, and the blade battery integrates safety and strength as part of the entire vehicle. The torsional stiffness will be doubled compared to a fuel vehicle, and there will be a significant improvement in driving control.
According to the above figure, in terms of structural design, the CTB battery body integration technology integrates the vehicle floor panel with the battery pack shell, which is integrated on the battery cover and the threshold, and the smooth sealing surface formed by the front and rear cross members is sealed through sealant to seal the passenger compartment, and the bottom is assembled with the vehicle body through mounting points. In other words, when designing and manufacturing the battery pack, BYD integrates the new generation of the Sea Lion’s battery system into the vehicle body as a whole. The sealing and waterproofing requirements of the battery itself can be met, and the sealing between the battery and the passenger cabin is relatively simple and the risk is controllable.
In August 2020, CATL announced that it was developing a new technology for battery chassis integration, which can enable electric vehicles to travel more than 800 kilometers on a single charge. This data was considered groundbreaking in the market where the general range was 300-400 kilometers at that time.
Currently, CATL is accelerating the research and development of CTC and announced plans to launch highly integrated CTC technology around 2025, and is expected to upgrade to the 5th generation of intelligent CTC around 2028.On January 26, 2022, CATL (Contemporary Amperex Technology Co., Ltd.) established a joint venture named “Suzhou Times New Energy Technology Co., Ltd.” with Shanghai Sidac Investment Management Co., Ltd., Suzhou Xinyue Zhonghe Business Consulting Center (Limited Partnership), and individual shareholder Jiang Yong in Suzhou City. The joint venture focuses on the development of electric vehicle drivetrain control systems. CATL invested RMB 1.35 billion and holds 54% of the shares of the joint venture. The legal representative of the joint venture, Jiang Yong, has nearly ten years of experience in the field of new energy vehicle motor and electric control. He previously served as the vice president of HC Technology and the chairman of HC Joint Power System Co., Ltd. Li Ping, the chairman of the joint venture, is also the co-founder and vice chairman of CATL. It is said that the core purpose of the establishment of Suzhou Times New Energy Technology Co., Ltd. is to promote the application of CTC (cell-to-chassis) technology, which integrates the cells and chassis of EVs. This technology integrates the motor, electric control, high-voltage DC/DC converter, on-board charger (OBC), and other components through an innovative architecture, and optimizes power distribution and reduces energy consumption through intelligent power domain controllers.
On February 15, 2022, Suzhou Times New Energy Technology Co., Ltd. signed a strategic cooperation agreement with Zhejiang Xin Ji Ao Automobile Co., Ltd. The cooperation is not only limited to the CTC chassis development, but also focuses on the joint production of CTC chassis based on the cooperation development. The two parties have even explored the possibility of local production of the “three electric” technologies for new energy commercial vehicles in Xin Ji Ao.
On February 19, 2022, the kickoff ceremony of CATL (Shanghai) Integrated Intelligent Electric Chassis Development Project and Raytronic Times (Shanghai) Intelligent Power System Project (Phase II) were held in Shanghai Lingang. The integrated intelligent electric chassis project is likely to accelerate the application of CTC technology.
On April 29, 2022, Cai Jianyong, the general manager of the intelligent vehicle control sector of Huawei’s Intelligent Automotive Solution Business Unit, resigned and joined CATL. He is now responsible for the integrated business of CTC batteries and chassis. Cai Jianyong has a strong resume in Huawei, previously serving as the CTO of Huawei’s Intelligent Automotive BU, mainly engaged in vehicle architecture and system design.
In addition, CATL is also recruiting talents in the fields of vehicle body architecture and chassis design. The recruitment website shows that CATL is currently hiring more than 20 positions related to vehicle chassis and architecture design.
CTC technology integrates cells, chassis, powertrain, and other systems, as well as autonomous driving related modules, and involves a complex industry chain, which will bring about a manufacturing revolution to the automotive industry.
Automakers:The OEMs consider that “the soul of the car cannot be entrusted to others”. The emergence of CTC will break through the limitations of PACK and directly involve the automotive chassis, which is the most critical and core component of the vehicle manufacturers’ accumulated advantages through long-term development. Battery companies/professional PACK companies find it difficult to develop independently. Although the technical barriers to developing new energy vehicle chassis have greatly declined compared to fuel vehicles, vehicle manufacturers still have significant advantages in development experience and technology. In the future development of CTC, OEMs with technological research and development advantages will have more dominant control; vehicle companies without development advantages will become contract manufacturers for mobile travel companies and also lose their dominant control over the chassis and other hardware. Vehicle manufacturers with lightweight asset operation and focusing on autonomous driving and technological travel services such as Baidu and Xiaomi will entrust third parties to lead CTC development. Meanwhile, car companies with the professional expertise and capabilities in body and battery research and development will have great potential.
Battery companies:
Compared with CTP technology, CTC technology requires battery manufacturers to be involved in vehicle design at an earlier stage. This requires battery companies to have stronger research and development and design capabilities to cooperate with some OEMs for in-depth development. Therefore, it is expected that more and more battery manufacturers will carry out deep cooperation with OEMs.
Moreover, battery companies lack development experience and technological accumulation in vehicle chassis. Although they have designs for CTC, there is still a need for lengthy accumulation to achieve breakthroughs in chassis technology. Controlling some professional chassis companies through mergers and acquisitions or equity participation to master chassis development technology may be an effective path for battery companies to achieve a CTC breakthrough more quickly. Currently, CATL is heavily recruiting talent related to automotive chassis technology; Guoxuan High-tech has also discussed CTC solutions with vehicle companies and believes that this is feasible within a limited scope but has not yet had a layout.
Chassis companies:
Professional chassis companies that master the development of chassis components and system integration technology have the possibility of independently developing CTC. On the other hand, they will also participate in CTC research and development led by vehicle manufacturers or battery manufacturers as suppliers. In addition, the emergence of third-party suppliers for electric chassis development, such as Yupao Technology and PIX Moving, creates new opportunities for the new energy vehicle market.
Other component companies:
Due to the high integration of CTC technology, metal structural parts such as longitudinal and transverse beams, module shells, reinforcing ribs, water cooling pipeline, etc., and plastic structural parts used for bearing, fixing, insulation and protection, pipeline connection, among others, will be greatly reduced or even directly eliminated from this industry. In addition, processing technologies such as welding and fastening connections will also be greatly reduced.
The demand and requirements for adhesive technology may increase. Some new materials and technologies such as thermal control protection materials and spraying require higher technological products to match.Besides, the technical requirements for battery cell will be higher, and in addition to the requirements for electrochemical performance, the requirements for structural strength and stiffness, equivalent to the technical threshold of battery cell have been raised.
In the future, the focus of integration will shift from the battery system to the electric chassis, and the integrated electric chassis technology will initiate independent technological iteration. It is expected that CTC technology will spark more innovations and technological requirements, and create revolutionary smart electric vehicles.
This article is a translation by ChatGPT of a Chinese report from 42HOW. If you have any questions about it, please email bd@42how.com.