Introduction: CTC technology is currently the trend of battery and vehicle integration in pure electric vehicles. However, promoting CTC is not an easy task. In fact, CTC is a solution with both advantages and disadvantages. Under the tide of intelligence and electrification, it is believed that as the technology becomes more mature, the automotive industry will innovate more business models and attract more new players to promote the development and improvement of technology.
Xiang Yanhuo, President of the Passenger Vehicle Solution Department of CATL China, revealed at the 10th Global New Energy Vehicle Conference that CATL will officially launch highly integrated CTC (Cell to Chassis) battery technology around 2025.
Coincidentally, many automakers have also proposed CTC technology routes. One is the structural battery announced by Musk at the Tesla Battery Day in September last year. The other is the CTC mentioned by both the traditional car giants Volvo and Volkswagen at the strategic development conference held in early July this year. Like Tesla, they also regard CTC as a key direction for future technology routes.
So, what is so mysterious about CTC?
Before we understand CTC technology, let’s first understand what CTP (module-free technology) is and the relationship between them.
CTP technology (module-free technology), also known as Cell To Pack, is a technology that reduces or eliminates the three-tier Pack structure of battery cells, modules, and packs. The CTP battery pack integrates the cells directly into the battery pack, and this type of battery integrates into the vehicle body floor as part of the vehicle’s structure, thereby eliminating the battery module. In China, it is called CTP. Compared with traditional battery packs, CTP can increase volume utilization by 15%-20%, reduce the number of parts by 40%, increase production efficiency by 50%, and reduce the manufacturing cost of power batteries.
Specifically, the battery module refers to a module composed of multiple related components. The battery pack (Pack) is composed of several modules, BMS, and distribution modules. For example, Tesla initially integrated more than 7,000 cells into several modules, which were finally installed in the battery box. This module process greatly reduces assembly complexity and improves production efficiency. In addition, modular design is conducive to power battery maintenance, making it easier to replace modules or components. However, the application of modules increases the quality and cost of the battery pack. Currently, BYD, HFC New Energy, and CATL are the main CTP technology adopters.Byd’s CTP technology for battery packs can increase battery capacity by 20% to 30% and extend battery life by 20% to 30%. Blade batteries, which rely on CTP technology, were first used in Byd’s Han EV electric car. Blade batteries have the advantages of high start-up exothermic temperature, slow temperature rise, low heat generation, and no oxygen release, based on innovative phosphate iron lithium technology. In addition, the length and thickness of blade batteries change, surface area increases, and overall heat dissipation improves. The short circuit of the battery is relatively long, which produces less heat, so the safety performance of blade batteries is excellent.
CNT’s CTP technology, which uses a non-modular scheme, can effectively shorten the production line and reduce waste in the production process. The battery cores are stacked online, tested, and then placed directly into the battery box, greatly reducing the flow process and traditional module frame welding. Compared with traditional 590 modules, CTP’s first generation reduces 24% of parts, and the second generation’s grouping efficiency is improved by 5-10%, space utilization rate is improved by 5%, and the number of parts is further reduced by 22%.
CATL’s CTP technology divides a large module into small spaces with several plastic heat dissipating sheets, which can be inserted into small spaces like a computer hard drive. Removing battery modules and directly integrating the battery into the battery pack can improve space utilization, reduce the weight of the battery pack, increase the energy density, and reduce the manufacturing cost compared with traditional batteries. Compared with traditional batteries, the capacity utilization of CTP battery packs increases by 15% to 20%, and the number of parts is reduced by 40%. The production efficiency is improved by 50%, and the energy density of batteries is increased by 10% to 15%, which will greatly reduce the manufacturing cost of power batteries. The battery pack is composed of at least two large modules, each of which is connected to the battery pallet by fasteners, and finally the battery pack is fixed to different cross beams.
Although CTP technology has many advantages, there are still some issues that need to be continuously improved. The first is the collision safety of the battery. Using CTP technology in the battery pack removes the side beams and the battery will directly bear the impact of collisions. Therefore, CTP battery packs need to have sufficient collision resistance.Next, battery thermal management is crucial to battery safety. Ningde Times’ various modules adopt CTP technology, where thermal conductive glue is filled in the center of the shell, and pressure or temperature sensors are placed between the sidewalls of the battery cell and the shell. It is used to detect changes in the shape and temperature of the battery, to eliminate battery malfunctions, and to measure thermal runaway phenomena in advance.
Then, will the after-sales maintenance cost and difficulty increase? Traditional battery packs have modules inside, and problems with the battery can be solved by replacing the battery module; once a battery pack without modules has problems, do we need to replace the entire pack? This may not be resolved by 4S stores and will likely involve returning the battery to the manufacturer for repair. However, some new energy battery manufacturers have indicated that their CTP technology has considered this issue, and their CTP can to some extent achieve the disassembly of battery cells to facilitate maintenance and stepwise utilization.
Finally, battery consistency is a difficult problem to solve in battery production and usage. Battery cells using CTP technology can be connected in series one by one by several smaller cells. Battery packs are composed of several hundred different cells, and the output is determined by the worst cell. How to monitor and control the charging and discharging status of each cell raises higher requirements for the battery management system (BMS).
Since the release of the first-generation CTP battery technology, innovative battery structures have become an important means for many battery companies to reduce costs and increase efficiency. The exposure of CTC technology further verifies that innovation of battery pack structures will be the mainstream development trend in the future until there is a revolutionary technological breakthrough in battery technology.
So, what is Ningde Times’ latest disclosed CTC technology?
The CTC battery integration solution directly integrates the battery cells into the internal floor frame, using the upper and lower plates of the floor as the battery shell. It is a further integration of CTP solution that fully utilizes the upper and lower plates of the floor to replace the battery shell and cover. It adopts an integrated design with the vehicle body floor and chassis, fundamentally changing the installation form of the battery.
The purpose of CTC technology is to achieve high integration and modularization, simplify the overall assembly process, and reduce costs, pursuing the integrated design concept of Apple. Under this concept, the convenience of maintenance is indeed a challenge. For the battery itself, it is assembled into a battery pack directly from the cells. The cells are encapsulated with a high-strength adhesive and wrapped with multiple layers of protective material; therefore, it is impossible to repair or replace individual cells. If there are problems, the entire battery pack must be replaced. As for the installation of the battery pack and the vehicle body, if maintenance or replacement of the battery pack is required, the seat crossbar needs to be removed, and the sealant needs to be removed, which makes maintenance relatively complicated. Further research is needed to address the convenience of maintenance.
Let’s take a look at the comparison of different battery integration technologies as shown in Figure 5 and Table 1.
The CTC battery technology has the highest space utilization rate and has a significant effect on the improvement of battery capacity. However, it is necessary to consider how to achieve sealing and battery load-bearing. Nevertheless, CTC is still the most effective solution to increase battery capacity under the condition that the existing battery technology remains unchanged.
Currently, the most important technical indicator and the highest concern for consumers in electric vehicles is the cruising range, and the most direct impact on the cruising range is the battery capacity. Therefore, increasing battery capacity has become the most effective solution to increase the cruising range of electric vehicles. In order to achieve higher capacity, the trend of battery integration has evolved from small module to large module, ultra-long module, and even to the module-free solution. This approach has to some extent improved the space utilization rate and increased the battery capacity. Nevertheless, in order to meet more stringent requirements, the concept of structured batteries is proposed to make the battery itself a part of the vehicle (similar to the idea of modern civil aviation aircraft making the entire wing into a fuel tank), that is, CTC, also known as the integration of battery and body.
CTC technology is currently the development trend of the integration of electric vehicle batteries and vehicles. However, promoting CTC is not an easy task. In fact, CTC is a solution with both advantages and disadvantages. We believe that under the trend of intelligence and electrification, as technology becomes more mature, the automotive industry will innovate more business models and more new players will emerge to promote the development and improvement of technology.
References:
[1] Zhang T. Application of CTC Integration Technology in Electric Vehicle Battery Layout[J]. Science and Technology Innovation, 2021(05):172-174.
[2] Zhu X Y. Application and Research on Non-Module Technology in Power Battery of New Energy Vehicle[J]. Science and Technology Innovation, 2020(15):159-161.
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.