EVs Battery Pack Technology Today and Development Trends
Electric vehicles (EVs) have become an increasingly popular transportation option today. As a result, the demand for high-performance and long-lasting EV batteries has increased drastically over the past few years. In response, manufacturers are investing heavily in research and development to improve the technology behind these batteries. In this blog, we’ll explore the latest advancements in EV battery pack technology and investigate future development trends that are driving the industry forward.
Q: What is the traditional battery pack technology?
The first-generation battery pack design was called CTM (Cell to Module). The meaning is that a certain number of battery cells are integrated into independent small battery modules, and then several modules are packaged into battery packs through physical partitions. It means that the battery cells, modules, battery packs, and integration into the vehicle need to be completed in sequence.
In this case, the vehicle manufacturer wanted to load more batteries in a limited space, so on the basis of the earliest CTM, it has made further requirements for standardized modules. Starting from Volkswagen Group, it has created 355 modules (355 refers to the length of the battery module, unit mm), which has promoted the Automotive industry in Germany Federation to develop VDA module standards. Common VDA modules include 355, 390, 590 modules, etc.
The advantage of CTM structure is that in the event of a collision or malfunction, it can minimize the heat transfer between modules and quickly shield the module. Moreover, the battery cell is fully protected by external structural components, resulting in good structural strength and low difficulty in grouping.
But the drawbacks of this design are also obvious. The cells in a single battery module require a large number of connectors and structural components, and there are also such problems between modules. I wanted to reduce the transmission between modules during accidents, but I didn’t expect such complex connecting cables to actually bring many hidden dangers. Moreover, the weight of the cables has always been very large, which is not beneficial for the overall lightweight of the vehicle, and the cost remains high. Moreover, the space utilization rate of the battery cell for the battery pack is only 40%, among which the space utilization rate of the battery cell for the module is 80%, and the space utilization rate of the module for the battery pack is 50%. The hardware cost of the module accounts for 15% of the total battery cost.
In order to solve the problem of the first generation CTM, the original structure was subtracted, resulting in the birth of the second-generation power battery pack structure CTP (Cell to Pack), which refers to the cancellation of the original small module design and the use of fewer large modules, or even the cancellation of module design and the direct integration of multiple cells to package the battery pack.
Q: Which advanced technology exists in the battery pack system?
At present, there are CTP， CTC and CTB technologies in the field of commercial or passenger vehicles.
CTP stands for Cell-to-Pack and refers to a technology that skips the standardized module design and directly integrates individual battery cells into the battery pack. This integration helps improve energy density and reduces the size and weight of the overall battery system. This technology is typically used in CATL(QILIN). With a record-breaking volume utilization efficiency of 72% and an energy density of up to 255 Wh/kg, it achieves the highest integration level worldwide so far, capable of delivering a range of over 1,000 km in a breeze.
CTC stands for Cell-to-Chassis and refers to a battery pack technology that integrates battery cells with the vehicle body, chassis, electric drive, and thermal management systems. The main difference between CTC and the traditional battery installation method is that the upper cover of the battery pack or the floor of the cockpit is canceled, thereby further simplifying the body cables and structural parts. This technology aims to improve the structural integrity of the battery system and reduce the weight of the overall EV.
Tesla’s 4680 is a typical of such application, uses hundreds of cylindrical battery cells and between every other row of cells is a cooling ribbon, much like a bandolier of bullets. Those bandoliers are placed in the cell tray a lid is placed on top, and then polyurethane foam is injected into the pack. The combination of the polyurethane foam and cells forms a super rigid monolithic structure.
CTB stands for Cell-to-Body, technology integrates the battery cell (typically is BYD blade cell) into the vehicle body. BYD’s CTB technology is similar to CTC, but with a slight difference. Both technologies place the battery cells directly in the chassis, but CTC considers the battery pack as a separate object that requires protection. In contrast, BYD’s CTB technology integrates the blade battery into the overall design of the car body, taking advantage of its high safety and structural strength. The blade battery cells and the entire battery pack form a structure that can function as a body structure similar to honeycomb aluminium.
Q: CTP vs CTC vs CTB
Let’s see the below table for the general comparison.
| Type | Technology | Typical Company | Advantage | Disadvantage |
| CTP | Cell-to-Pack (Large Module) | CATL | Improve the volume energy density and weight energy density of battery packs, reduce costs | High consistency requirements for battery cells, making it difficult to repair and replace battery cells |
| CTC | Cell-to-Chassis | Tesla | Increase the Z-axis space inside the car, increase distance range, and reduce costs | There is still significant room for improvement in integration; High difficulty in battery cell maintenance and replacement |
| CTB | Cell-to-Body | BYD | Increase the Z-axis space inside the car, increase distance range, reduce costs, improve body rigidity, and improve safety and controllability | There is still room for improvement in integration |
Q: Which technology has more development prospects?
From the current perspective, the trend is definitely towards high integration, reducing components, bringing greater space, and reducing costs. However, the direct integration of CTC/CTB with the chassis is not feasible for swapping batteries. If the continuous development of considering battery swap, CTP will become the starting point for further optimization.
In automobiles, the path of high integration is not only battery systems, but also all aspects of electric vehicles, such as the integration of electronic and electrical architecture (EEA).
So, we see that CTP is just a battery pack technology, while CTC and CTB are a type of vehicle technology. Although in terms of integration, CTB is slightly inferior to Tesla’s CTC solution, which means BYD’s manufacturing cost will be slightly higher than Tesla’s. However, in terms of structural safety and maintainability, BYD’s CTB is still superior, which is clearly more advantageous for users.
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