3.7v 18650 battery pack

Will 3.7v 18650 battery packmodule-less technology become mainstream?

How to reduce the cost of 3.7v 18650 battery packsystem?

Increase the weight of battery cells and structural parts, improve automation efficiency...

There is another way to cancel the battery module.

At the 2019 Frankfurt International Auto Show in Germany, CATL launched a new CTP highly integrated 3.7v 18650 battery packdevelopment platform (Cell To Pack), in which batteries are directly integrated into the battery pack.

CATL is not the first domestic company to release CTP technology. As early as July 9, Honeycomb Energy released this technology. In addition, BYD is also developing it in China.

Industry insiders have raised some doubts about CTP safety, lifespan, after-sales service and step utilization. However, according to the "Electric Vehicle Observer", battery companies have also found solutions to the above problems.

Let’s take a closer look at what kind of technology CTP is? Why do so many battery companies choose this technology? Will this technology become a new trend in the future?

1. What is the use of the module?

Since it is said that the module is directly integrated into the battery pack, it is necessary to clarify the function of the module.

The so-called module is to form a module with some related parts, which can also be understood as the concept of a collection of parts and an assembly. For example, the front-end radiator module of a traditional vehicle, the electronics industry will also have functional integrated modules called modules. In the field of battery packs, several cells, conductive rows, sampling units and some necessary structural support components are integrated together to form a module, also called a module.

Ternary 3.7v 18650 battery packmodule

In the early days, some 3.7v 18650 battery packpacks used cylindrical cells. For example, Tesla used more than 7,000 cells. If they were directly assembled into the battery box, the assembly complexity would be greatly increased and the production efficiency would be very low. Therefore, some cells were Pre-integration becomes very important. This is also one of the important reasons for the production of battery modules.

Another advantage of the module is that the modular design facilitates after-sales maintenance and allows the replacement of a single module or module.

Just like two sides of a coin, the application of modules also has to add some additional parts, and the more modules there are, the more additional parts there will be. These additional components will increase the cost and weight of the battery pack.

Similar to this is Tesla. Tesla initially used more than 10 modules, but now only uses four large-size modules on Model 3, greatly reducing redundant parts. In addition, the application of large-capacity square aluminum shell batteries, battery core technology innovation, and improved production consistency also provide opportunities for module removal.

2. CTP has obvious advantages in cost reduction and density improvement.

What exactly are the effects of canceling the module?

Data from CATL shows that the volume utilization rate of CTP battery packs has increased by 15%-20%, the number of battery pack components has been reduced by 40%, production efficiency has increased by 50%, and the energy density of battery packs has increased by 10%-15%, reaching More than 200Wh/kg, significantly reducing the manufacturing cost of power batteries.

Introduction to CATL CTP

Honeycomb’s data is that compared with the traditional 590 module, the first generation of CTP reduced the number of parts by 24%, the second generation group efficiency increased by 5-10%, the space utilization increased by 5%, and the number of parts was reduced by another 22%. .

Introduction to Honeycomb Energy CTP

From only two sets of promotional data, it is difficult to tell the advantages and disadvantages of the two technologies, but the two CTPs do perform well in terms of reducing parts and increasing energy density.

Another advantage of the moduleless approach is the simplification of the product production process. A person related to Honeycomb Energy told the "Electric Vehicle Observer" that the traditional technology is that cells are formed into modules through a certain frame structure, and the modules need to be tested offline and then stored and transported. If the PACK and module are not in the same factory, additional storage, incoming inspection, online inspection and other processes are required. These processes require the investment of resources such as manpower, equipment, and space.

The module-free solution can effectively shorten the production line and reduce process waste. The cells are stacked online and inspected online, and placed directly into the battery box, which greatly reduces the circulation process and also reduces the frame welding process of traditional modules. Among them, the welding equipment alone will cost millions of yuan.

3. Some concerns of people in the industry

In the eyes of many people in the industry, CTP is not a new technology. It was previously used in the field of lithium iron phosphate and buses. Due to the large battery arrangement space in buses, lithium iron phosphate batteries have strong stability and are widely used.

But it is completely different from the combination of passenger cars + lithium iron phosphate. Most of this CTP technology will be used in the field of passenger cars, most likely in ternary batteries. For example, CATL cooperates with BAIC New Energy to use ternary batteries. Because of this, some people in the industry have also raised several doubts about this technology.

○The thermal stability of ternary batteries is poor, how to improve safety?

According to Mr. Ma, the relevant person in charge of a battery system manufacturer, in traditional battery packs, there is a certain distance between modules, which can be used for heat dissipation. The module itself also has a thermal insulation design, taking targeted measures against the heat flow, air flow, and erupted conductive substances generated by the thermal runaway of the single unit, which has a certain inhibitory effect on the spread of thermal runaway. CTP becomes a "large module". Will the reserved space be insufficient?

According to honeycomb related technicians, good heat dissipation and insulation are the advantages of CTP. "Early modules used lithium iron phosphate batteries to form modules with a VDA specification length of 355mm. Due to their high stability, sufficient thermal insulation gaps were not considered; later modules similar to Volkswagen MEB specifications with a length of 590mm were limited by Affected by the specifications, the choice of thermal insulation buffer materials between battery cells is limited, and we can only seek some small-sized and high-performance materials. In order to meet the safety requirements, we have to pay a relatively high cost."

The technician added: “Relatively speaking, CTP can bring more space by reducing some parts, and its own size is relatively less restricted, so it can obtain a relatively large gap space, making the selection of materials more efficient. More possibilities, resulting in lower costs.”

CATL’s solution to this is unclear. However, the person in charge of the battery department of a relevant car company revealed that CATL has also reserved some space in the battery pack for heat dissipation, and the overall effect is acceptable.

○Does CTP have an impact on lifespan?

For ternary batteries, traditional modules have a pre-tightening force (the cells will expand after cycling, and life span will be affected if they are not restrained; if restrained too tightly, the same life span will be reduced or safety issues will arise) designed to ensure the service life of the battery. And this preload force has been verified experimentally. The multi-cell integrated design of CTP increases the difficulty of setting the preload force. Will it affect the life of the battery cells?

In this regard, Honeycomb technicians said that Honeycomb's CTP inherits the integration experience of traditional modules in the integration technology. It directly applies a certain preload force to the battery core through the box. At the same time, it will apply flexible space advantages to allow the battery core to expand appropriately. This improves the impact of integration on battery life and increases the life of the battery system.

Honeycomb’s module-less battery pack exhibited in Frankfurt

○Will the after-sales maintenance cost and the difficulty of tiered utilization increase?

Mr. Ma believes that traditional battery packs have modules inside, and when battery problems occur, they can be solved by replacing the battery modules. Once there is a problem with a module-less battery pack, should the entire pack be replaced? I'm afraid this cannot be solved by 4S stores. It will most likely be returned to the battery manufacturer for repair. Will after-sales costs increase significantly?

Han Feng, deputy chief engineer of new energy power technology at Changan Automobile Auchan Research Institute, also said that generally not all cells of retired power batteries are damaged. In traditional battery packs with modules, only the modules with damaged cells need to be picked out, and other modules with no problems can be directly used in echelons. However, without the module, it becomes more difficult to remove damaged cells, and it becomes very troublesome to use them step by step.

Regarding the above two problems, I don’t know if CATL has any solutions. However, Honeycomb Energy stated that their CTP technology has considered this problem. On the one hand, they ensure the consistency of the battery cells through strict process control to reduce the failure rate; on the other hand, their CTP can achieve battery life to a certain extent. The core can be disassembled to facilitate maintenance and subsequent use.

Indeed, if a single faulty battery cell can be accurately identified and a single battery cell can be dismantled and replaced by front-line maintenance personnel, the maintenance cost will definitely be lower than replacing the module.

4. Can it become a development trend?

Module-less battery packs seem to be able to find solutions to several concerns raised by industry insiders. Will this solution really be accepted by more and more OEMs?

Han Feng admitted that this technology is still very attractive to enterprises. The price of CATL's power batteries using this technology is no longer so high and can be on par with the second-tier battery companies. "For vehicle manufacturers, they naturally want to buy better products at lower prices."

Han Feng believes that as an OEM, the first thing to consider is cost reduction. Especially when subsidies are significantly reduced, the cost pressure from vehicle companies will be directly passed on to battery companies, and battery companies must have a response plan.

At present, the CTP solutions provided by some battery companies can reduce the cost of battery packs by approximately 0.1 yuan/Wh. Especially in the field of lithium iron phosphate batteries, which has extremely demanding price requirements, this decline is indeed significant.

In the process of reducing the cost of power lithium-ion batteries, various technologies and routes have emerged, and the methods are not limited to battery cell integration, but also include material selection, process optimization, standardization, large modules, etc. For example, the early A123 used cable ties; the Leaf used soft packages to integrate small modules, integrate large modules and then integrate PACK; the standard VDA355mm length module was the first to be launched abroad, and Volkswagen launched the MEB590mm length module; Tesla even more Create a super large module nearly 2 meters long.

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