In fact, soft-pack batteries are not a brand-new thing. The reasons why cylindrical and prismatic batteries have become mainstream are related to cost, research and development cycle, etc. As early as 2010, Qiantu Motor established a technical route based on standard boxes of soft-packed batteries. Zhai Sheng mentioned: "As a vehicle developer, the safety and consistency of batteries are our first core issues to consider." For this reason, Qiantu Motor abandoned the cylindrical and square single cells used in the mainstream market at that time, and proactively adopted soft-pack batteries with higher safety and obvious advantages in energy buffering and release.

　　Compared with cylindrical and square batteries with fixed shapes, due to the aluminum-plastic film packaging, soft-pack batteries will undergo a slow-release process when the internal energy is gathered and reaches the explosion point, rather than a sudden explosion. Simply put, it is the internal energy of the soft-pack battery. A short circuit will not explode immediately, but will expand and release energy first, thereby providing passengers with more ample time to react and escape after the vehicle alarms. Higher safety advantages make soft-pack batteries the research and development foundation for Qiantu Motor's entire power battery technology path.

　　From the perspective of OEMs, soft-pack batteries have gradually gained favor from more first-tier manufacturers after their development in recent years. General Motors, Nissan, Mercedes-Benz, and Audi have all invested in the research and development and adaptation of soft-pack power batteries. . Currently, the world's best-selling affordable electric vehicle, the Nissan Leaf, is also equipped with soft-pack batteries. From the supplier level, suppliers led by large-scale battery cell manufacturers such as CATL and LG are increasingly participating in the research and development and manufacturing of soft-pack batteries.

　　Innovative standard battery box

　　A few days ago, a series of spontaneous combustion incidents of electric vehicles caused some psychological distress to the public. Taking cylindrical batteries as an example, since the main heat source of the battery is located at the pole ears, and the cooling circuit laid under the battery pack is difficult to balance the temperature difference between the upper and lower parts of the battery, the cylindrical battery pack has the inherent disadvantage of having difficulty in BMS thermal management. Coupled with the aging of the battery after years of use, the diaphragm of a battery is punctured under the influence of lithium dendrites, resulting in an internal short circuit, which is prone to a domino-like thermal runaway, causing a chain reaction of the battery pack. Now, in order to ensure the energy density of the battery pack, the cells are arranged very closely, which once again increases the risk of thermal runaway. From this we know that in addition to the safety of individual batteries, the safety measures between batteries, that is, the overall battery pack, are also particularly important.

　　Standard battery box designed by Qiantu Motor

　　Faced with this problem, Qiantu Motor adopts a standard battery box design. Since the battery cells will undergo slight volume changes during charging and discharging, we call it the "breathing effect." Inside the Qiantu standard battery box, a buffer design is used between the cells to absorb the size changes caused by the breathing effect of the cells. And form an internal buffer in the event of collisions, bumps, etc.

　　The exterior of the battery box is made of a high-strength composite material casing, which makes its crash performance test score 30% higher than the national standard and meets the IP67 protection level requirements. It is worth mentioning that the sealed shell of the standard battery box can also efficiently cooperate with the battery thermal management system to ensure the consistency of battery cell temperature.

　　Taking the Qiantu K50 as an example, its power battery pack is composed of 10 standard boxes connected in series, with a total energy of 78.84kWh. This is also a modular design idea. With the standard box, the battery packs of the vehicle can be arranged and combined relatively freely. Qiantu K50 is positioned as a high-performance sports car, so it uses this T-shaped combination to take into account the vehicle's endurance, control and space utilization. In addition, a great advantage of standard battery boxes in terms of safety is that each single standard battery box is equipped with an independent thermal management system and an independent battery management system, which not only provides the standard battery box with more efficient heat dissipation performance and structural strength, but also Effectively realize intelligent management of battery cells and monitor the battery status of each battery box throughout its life cycle in real time.

　　RESS rechargeable energy storage system

　　Relying on high-security standard battery box packs, Qiantu Motor is matched with an efficient thermal management system and a sophisticated and intelligent battery management system to form a comprehensive safety performance solution for the vehicle's RESS rechargeable energy storage system. The RESS system uses an active liquid cooling/liquid heating thermal management system to ensure that each standard box can receive sufficient heat exchange, minimize the temperature difference between cells, effectively improve temperature consistency, and ensure the full temperature of the vehicle (-30 ℃ ~ 55 ℃) safe driving range.

　　Qiantu Motor RESS rechargeable energy storage system

　　This BMS thermal management idea is like a 10-core CPU. Each core is responsible for its own standard box and independently controls its cooling or PTC heating. Compared with the traditional "one-size-fits-all" management method of highly integrated battery packs, this decentralized management can extend the service life of the battery to a certain extent while providing better safety. Even if something goes wrong with a certain standard box, the BMS slave control module can independently cut off its work; if the situation is extremely serious and still cannot be controlled, the main control module will immediately shut down all standard boxes. It can be said that Qiantu Motor defends against thermal runaway from three dimensions: battery cells, battery packs, and thermal management.

　　Production ideas in self-built factories

　　Maybe you don't know much about it, but the supply of battery cells is sometimes like going to a restaurant to eat food, it also depends on the "season". The same dish may taste different when eaten in different seasons. The same is true for the supply of battery cells. Due to the processing of raw materials, there may be slight differences in telecommunications products of the same model from the same manufacturer in different batches and in different months. If mixed, it will affect the status of the battery pack.

　　In order to ensure the consistency of battery products, Qiantu Motor built its own factory and designed its own assembly lines to develop and produce the entire battery system. At the same time, Qiantu also extended its supervision system to raw material suppliers, and proposed that the electrolyte and positive and negative electrode materials required for the battery cells in the same standard box system must be assembled from the same manufacturer and the same batch to avoid small differences in raw materials. If the battery performance difference occurs, try to improve the internal consistency of the battery standard box.

　　Summarize

　　This Qiantu Living Room lecture is more like an objective response to the previous spontaneous combustion incident of electric vehicles. In fact, we are always used to facing electric vehicles with a one-size-fits-all attitude, and if one car burns, others will burn. After in-depth understanding, you will find that there are so many ways to use batteries. Although the process difficulty and cost of soft-pack batteries are slightly higher, many manufacturers choose ready-made cylindrical/square battery pack solutions, but the safety of soft-pack batteries The advantages in performance and service life are also obvious. I believe that in the future, everyone can calm down and not blindly pursue higher energy density, but choose a more reasonable cruising range while ensuring safety. By then, soft-pack batteries will become the technical solution chosen by more car manufacturers.

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