As the "heart" of new energy vehicles, power battery system not only determines the performance of a vehicle, but also represents the research results of battery manufacturing technology of vehicle enterprises. GM, an old car company, has been struggling in the field of new energy for decades. How's the research going? What are the core achievements? Is safety guaranteed? These are all concerns of consumers. You can know a thing or two by visiting the factory directly.
Parker went to "explore the factory" this time, mainly aiming at Buick Micro Blue 7 and Micro Blue 6? The research, development, experiment and manufacturing process of PHEV power battery system were visited on the spot. Let's briefly review the next two models, both of which were listed in July this year. Among them, the light blue 7 pure electric SUV is equipped with a 55.6kWh battery pack with a cruising range of 500 kilometers. The light blue 6 plug-in hybrid vehicle adopts the power combination of 1.5L naturally aspirated engine and dual motors, and the total motor power reaches 13 1kW.
The modular high-performance ternary lithium battery cells carried by the two cars are obtained by further optimizing the exclusive formula and design of SAIC-GM on the basis of LG chemical technology scheme, with higher energy density, longer service life and better temperature adaptability.
General Motors has independent battery laboratories in the United States and China. In these laboratories, it has established its own battery trial production line for battery prototype development and various types of testing and certification. SAIC-GM Power Battery System Development Center was established in Jinqiao, Pudong, Shanghai on 20 15. It is GM's second battery assembly center in the world and the first battery assembly center outside North America. Specializing in battery system design, research and development, testing and production. The planned product line covers all new energy vehicle batteries such as light hybrid, full hybrid, plug-in hybrid (including extended range) and pure electric.
In SAIC-GM battery lab, Parker saw the specific structure of battery module, from a small MINI stacking unit to a complete power battery module, which required numerous tests by researchers. It is reported that micro blue 7 and micro blue 6? The battery of PHEV has passed various limit tests such as extrusion, collision, immersion, fire, overcharge, overdischarge, short circuit, salt spray, etc. 10, and simulated the working conditions in extremely hot, extremely cold and high altitude areas under the environmental cabin with the temperature difference of -40℃ to 85℃, thus ensuring the structural safety of the battery. The battery pack will also undergo 100 system and vehicle tests, covering mechanical, thermodynamic, electrical, life, performance and other aspects to ensure the safety of the battery pack in its longer life cycle.
In addition, the battery pack of Buick Micro Blue 7 uses foam to isolate the heat dissipation between batteries, which relieves the expansion of batteries during later charging; The battery cell frame and radiator are fastened with long bolts to ensure the stacking stability of batteries. ?
The highlight of two-car battery technology lies in GM's exclusive battery-level intelligent temperature management system and safety system. Due to the different requirements of the structure, shape and performance of the two cars, the design of the above system will be adjusted, but the overall idea is similar.
Micro Blue 7 arranges a heat conducting sheet between every two batteries, which is directly connected with the water cooling structure at the bottom of the battery pack, and can realize active cooling or heating according to the battery working conditions, thus ensuring temperature uniformity and low-temperature discharge performance. At the same time, the water inlet and outlet pipes of the water-cooling structure at the bottom of the battery pack adopt a double-channel serpentine design, and the battery pack can still maintain stable working performance at the ambient temperature of -35℃~55℃.
Light blue 6? PHEV battery pack adopts layered liquid cooling technology patented by General Motors, and there is a heat conduction sheet with capillary liquid cooling tube between every two batteries, the thickness of which is only 0.2 mm, and the cooling liquid can flow in the capillary to accelerate heat conduction more efficiently. In addition, its environmental temperature adaptation range is also between -35℃ and 55℃.
The waterproof and fireproof performance of new energy vehicles has always been concerned, especially since the summer, spontaneous combustion accidents of new energy vehicles have occurred continuously, and this year's "flood" has made consumers pay more attention to the safety protection degree of vehicles. Light blue 7 and light blue 6? The battery pack of PHEV has reached the sealing level of IP67, and can be immersed in 1 m for 30 minutes, which ensures the safe operation of the battery pack when the vehicle wades.
It is worth mentioning that the bottom of the micro blue 7 battery pack is also designed with a steel tray with reinforcing ribs, which can protect the internal battery pack from being squeezed in the event of collision, thus minimizing the risk of spontaneous combustion. In addition to the battery tray, the micro blue 7 fuselage also adopts a high-performance BFI integrated fuselage structure, and the application ratio of high-strength steel is as high as 78%. Ultra-high-strength thermoformed steel (PHS) with tensile strength of 1500Mpa is used for A-pillar, B-pillar, inner plate of hinge pillar, sliding plate, front and rear longitudinal beams, etc.
Buick light blue 6? The high-voltage wiring harness in the front cabin of PHEV adopts transverse outgoing wires to ensure the integrity of the high-voltage wiring harness during collision. At the same time, the connection part of the high-voltage wire harness adopts a secondary locking structure to avoid the looseness and accidental touch of the high-voltage wire. In addition, its dual redundant active power-off function can disconnect the relay within 1 second after the collision, complete the active discharge and reduce the voltage to below 60V within 5 seconds (the national standard requires 60s), and can forcibly shut down the high-voltage system and airbag system outside the vehicle.
The total number of employees in the whole battery pack production workshop is relatively small, which is also due to the introduction of automatic operation. The whole process of charging, assembling, transporting and testing of batteries and modules is intelligently completed by robots or manipulators, and the automation rate reaches 100%, which greatly improves the reliability.
Of course, the digitization rate of workshops is also very high. Every key component can realize real-time data collection, monitoring and early warning in the assembly process, and can fully trace product information while ensuring orderly production. These "identity cards" will be kept for more than 2 years.
On the production line, Parker also noticed a mechanical part different from ordinary fusion welding, and asked that it was an ultrasonic welding device for welding tabs. Compared with fusion welding, it would not cause high-temperature pollution and damage to semiconductors and other materials, thus reducing the risk of welding tabs tearing. Under the guidance of the vision system, the industrial robot accurately locates and automatically controls the ultrasonic welding head to complete the welding of the positive and negative tabs of the battery cell, so that the battery module forms a channel.
In the process of battery assembly, it will be divided into three levels: battery core, module and battery pack, which need to be tested and evaluated from the aspects of functionality, electrical performance and electrical insulation. To ensure Buick Blue 6? There is no leakage point in the liquid-cooled heat conducting fin of PHEV and the liquid-cooled loop system of Micro Blue 7, and the module assembly line will adopt the mass flow method for leakage test. At this point, a complete set of power battery modules has been assembled.
The process of "exploring the factory" is urgent, and it only takes one day to learn more about the research results of SAIC-GM power battery technology. But visitors can feel micro blue 7 and micro blue 6 by visiting the factory on the spot. PHEV has invested a lot of money in battery research and development. At the same time, Parker believes that there are also some shortcomings. For example, the on-site staff revealed that the daily output of battery packs of the two cars is only about 30-60 units. In the case of future sales increase, this capacity still needs to be further improved.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.