How to build a safe battery pack for a supercar?

As electric vehicles continue to catch fire, the safety of batteries and electric vehicles as a whole has been pushed to the forefront. As a member of the new car-making forces, Qiantu, whose parent company is Great Wall Huaguan, can be said to be a relatively special one. First of all, it started with a supercar model K50. At Qiantu's experience store in Sanlitun, we had an in-depth understanding of Qiantu's power battery technology and development, as well as their thoughts and solutions for battery safety from Zhai Sheng, Qiantu Automobile's three-electric technology expert and general manager of Walt Division.

The original intention of taking safety as the core determines the R&D route

Since we are making a supercar, performance is naturally the first feature we think of for this car. However, in the design of the entire battery, the priority of future considerations is from safety to performance to cost, and safety has long been mentioned above performance.

Therefore, after comprehensive consideration, Qiantu Motors chose soft-pack structure batteries with higher safety and more obvious advantages in energy buffering and release as the research and development basis, and used ternary materials for the battery cells, with a single cell energy density of 223.58Wh/kg (battery packs can exceed 140Wh/kg). The reason why the cylindrical and square single cells used in the mainstream market at the time were abandoned was because the former would be unstable and have a relatively low cycle life after too much stacking, and the latter would not be able to ensure the consistency of battery temperature after the energy density was increased.

However, when the aluminum-plastic film packaging is used, the soft-pack battery will experience a slow release process when the internal energy accumulates and reaches the explosion point, rather than a sudden explosion. The original millisecond-level electrochemical reaction will be converted into a deformation reaction of about ten seconds, thereby achieving slow energy release. This provides passengers with very precious reaction and escape time after the vehicle alarm sounds.

In addition to the safety of single cells, Qiantu Motors also pays attention to the safety performance of the entire battery module. Unlike other battery pack designs, Qiantu has pioneered the use of a standard battery box design, with 10 battery boxes installed on the entire Qiantu K50. Inside the Qiantu standard battery box, the dynamic space of the battery cell adopts a buffer design that can absorb the size changes caused by the breathing effect of the battery cell and form an internal buffer in the event of collisions, bumps, etc.

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

Another element of safety: consistency

The current demand for electric vehicles and the upstream production, safety and other comprehensive factors have determined that it is impossible to make a battery into a whole and place it in the car, so there is the concept of the current battery pack, which also makes the battery module have more safety hazards due to more monomers, connections, structural design, etc. Therefore, consistency is another important aspect to ensure the safety of electric vehicles.

Just now we talked about the battery box of Qiantu. Although it seems inconsistent to split a whole battery pack into 10 parts, this is because each battery box has its own independent management system, which conducts comprehensive monitoring of the battery status of each battery box throughout its life cycle, including detection, monitoring, safety protection, charging management and other functions. Therefore, as long as the manufacturing standards are guaranteed, it is equivalent to monitoring the entire battery pack to ensure unified management of the entire battery pack.

The entire system, including thermal management and battery management, is the RESS rechargeable energy storage system for the future vehicle. The RESS system uses an active liquid cooling/liquid heating thermal management system to ensure that each standard box can get sufficient heat exchange, minimize the temperature difference between the cells, effectively improve the temperature consistency, and ensure that the vehicle's full temperature is within a safe range of -30°C to 55°C.

In order to ensure the consistency of battery products, Qiantu Motors built its own factory and independently designed an industry-leading assembly line to develop the entire battery system. On each production line, the company uses an automated ratio of 58 robotic arms and 6 workers to ensure the production, inspection, process level and quality of the production line. At the same time, Qiantu also reaches out to the "suppliers of suppliers". The electrolyte, positive and negative electrode materials required for the battery cells in the same standard box must be assembled from the same manufacturer, the same batch, and the same month to avoid differences in battery cell performance caused by small differences in raw materials, thus ensuring battery consistency from the source.

Car Cloud Summary

As early as 2010, Qiantu Motors had already laid out its plans in the field of power batteries, placing battery research and development at the forefront of vehicle design at the beginning of car manufacturing. With the advancement of battery technology, we believe that accidents caused by batteries will inevitably be further reduced. Concepts like Qiantu will make us more confident about the product itself. In the future, after this electric supercar, Qiantu will also launch more pure electric models covering other market segments, and we are of course looking forward to Qiantu launching more ordinary household products.