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[Battery] In-depth analysis of Battery cells, Battery modules and Battery packs CTP/CTC

Battery system is the core of electric vehicles and energy storage. As the three core layers of the battery cell, module and pack, they are closely related to each other and jointly shape the performance of the battery system.

Xiaowei will analyze the relationship between them and their respective advantages and disadvantages from various dimensions, such as technology, cost, safety and maintenance.

I. Relationship between the three

1.Battery Cells:

As the smallest component of a battery cell, the battery cell is undoubtedly the foundation of energy storage. Common battery cells on the market come in a variety of shapes, including cylindrical (such as the 18650,21700 and 4680 models used by Tesla), prismatic battery cell (many CATL products), and pouch cells.

2.Battery Module

A module is a smart combination of battery cells connected in series and parallel, to which auxiliary components such as structural frames, heat sinks, and voltage/temperature sensors are added to form a unit that can be managed independently.

3.Battery Pack

A battery pack is a combination of several modules (or, in some advanced technologies, directly integrated battery cells). It contains key components such as the battery management system (BMS), thermal management system, high-voltage circuits, and enclosure, and is a complete system capable of supplying power directly to the outside world.

4.Hierarchical relationship

In the traditional battery structure, there is a clear hierarchical relationship of “battery cell→module→battery pack”. However, with the rapid development of technology, CTP (Cell to Pack)/CTC (Cell to Chassis) technology came into being, which breaks the traditional mode, realizes the direct leap of “battery cell → battery pack”, and cleverly skips the link of module.

II. Comparison of strengths and weaknesses

1.Battery Cells

Advantages

1- As the cornerstone of the entire battery system, the performance of the battery cell itself, such as energy density, cycle life and other key indicators, will directly have a decisive impact on the overall performance of the battery system.

2- Battery cells are highly flexible and can be flexibly designed to fit different chemical systems, such as lithium ternary, lithium iron phosphate, etc., according to different actual needs.

3- Thanks to the standardized mass production mode, the production cost of battery cell can be effectively controlled.

Disadvantages

1- Individual battery cells can not be put into use independently due to their own characteristic limitations, and must be built into modules or battery packs through a combination of ways in order to play a role.

2- The consistency of battery cells is extremely stringent, once the consistency of the battery cells deviates, the overall performance of the module and even the battery pack will be seriously dragged down.

2.Battery Module

Advantages

1- Outstanding maintainability: when a single module fails, it can be easily replaced, thus greatly reducing maintenance costs.

2- High Design Flexibility: The design concept of modularization makes it easy to adjust the capacity of the battery pack, for example, by increasing or decreasing the number of modules.

3- Guaranteed safety: Inside the module, battery cells can significantly reduce the risk of thermal runaway spreading through well-designed isolation and heat dissipation measures.

Disadvantages

1- Poor space utilization: the structural parts of the module, such as frames and connectors, will occupy a certain amount of space, which leads to a reduction in the energy density of the battery system.

2- Cost increase: the assembly process of the module requires additional materials and complex processes, which undoubtedly increases the production cost.

3- Increase in weight: The presence of structural components increases the overall weight of the battery pack.

3.Battery Pack

Advantages

1- Significant advantages in high integration: With advanced technologies such as CTP (Cell to Pack) or CTC (Cell to Chassis), the module structure has been successfully eliminated and the energy density has been significantly increased, typical examples are BYD Blade Battery and Tesla 4680 Battery.

2- Comprehensive system optimization: BMS and thermal management system are integrated inside the battery pack, which can accurately monitor and effectively balance the status of battery cells from a global perspective.

3- Excellent protection: The well-designed shell has excellent impact resistance, waterproof and fireproof performance, which greatly improves the safety of the battery system.

Disadvantages

1- Increased maintenance difficulty: after the elimination of modules, once a single battery cell malfunctions, the entire battery pack often needs to be repaired.

2- Soaring design complexity: The design of battery packs requires comprehensive integration of battery cells, heat dissipation, structural strength and many other complex factors, which undoubtedly greatly increases the difficulty of research and development.

3- High cost: the integration process, such as laser welding, and the related equipment, the initial investment is huge.

III. Technology trends: de-modularization (CTP/CTC)

1.CTP(Cell to Pack)

CTP technology realizes the direct integration of battery cells into battery packs without the need to go through the intermediate link of modules, CATL, BYD and other companies have achieved remarkable results in this regard.

Advantage:With this technology, energy density can be increased by 10% – 15%, while effectively reducing production costs.

Challenges: The technology imposes harsh requirements on battery cell consistency and thermal management.

2.CTC(Cell to Chassis)

CTC technology goes one step further by integrating the battery cell directly into the vehicle chassis, as exemplified by the Tesla 4680 battery.

Benefits: This integration further achieves weight and cost savings while significantly improving the structural strength of the vehicle.

Challenge: CTC technology is virtually impossible to service, and therefore relies heavily on battery life prediction.

IV. Comparison of application scenarios

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V. Summary

Hierarchy:

The battery cell serves as the foundation for the entire battery system; the module serves as a transition unit, bridging the gap between the battery cell and the battery pack; and the battery pack is the final market-oriented product that is put into practical application.

Balance of Advantages and Disadvantages

Modularized design sacrifices energy density to a certain extent, but in exchange for good maintainability; while de-modularized design focuses on improving energy density and compromises on maintainability.

Future Direction

With the continuous breakthroughs in battery cell technology (e.g., solid-state batteries) and the optimization and upgrading of BMS algorithms, highly integrated CTP/CTC technology will undoubtedly become the mainstream development direction in the future. However, in some specific application scenarios, such as energy storage, modular design still occupies an important place by virtue of its unique advantages.

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