According to Lei Fengwang, there is no doubt that the power battery system is the most crucial part of the electrification technology for new energy vehicles.
Meanwhile, with the further opening of the electric vehicle market, the frequent incidents of electric vehicle spontaneous combustion in recent years are also stirring up public nerves.
How to make batteries safer has become a difficult problem that major manufacturers are committed to answering.
On August 20th, Lei Fengwang had the privilege of visiting the SAIC General Motors Power Battery Development Center.
As an important strategic layout of Buick’s “electrification, networking, intelligence, and sharing” strategy, the battery packs of Buick’s Micro Blue 7 and Micro Blue 6 PHEV models, as well as the mysterious veil of the battery pack production line, have also been unveiled.
In fact, in April 2019, Buick officially launched the Micro Blue 6 pure electric model, which was Buick’s first pure electric product in China.
However, at that time, the battery capacity of this car was 35kwh, and the NEDC range was only 301km.
In just July, Buick launched the Micro Blue 6 PHEV, equipped with Buick’s new eMotin intelligent electric drive system.
At the same time, the pure electric SUV Micro Blue 7 was launched, based on the general second-generation pure electric platform, equipped with a 55.6kWh battery pack, and a NEDC range of 500km.
Unlike most car companies that simply purchase batteries from battery suppliers for assembly, SAIC General Motors leans towards a deep involvement in battery cell development and long-term cooperation with battery suppliers to develop batteries.
For example, the Buick Micro Blue 7 and Micro Blue 6 PHEVs mentioned earlier use ternary lithium batteries that are further optimized in formula and design based on LG Chemical’s technology, resulting in higher energy density and longer battery life.
The Micro Blue 7 (left) and Micro Blue 6 PHEV (right) are equipped with a new generation of modular high-performance ternary lithium-ion battery packs. To some extent, abnormal temperature is one of the biggest causes of battery safety accidents.
In response, the Buick Micro Blue 7 and Micro Blue 6 PHEV power battery systems adopt General Motors’ exclusive battery level intelligent temperature management system, and have been customized according to the structure, design, performance, and other needs of each car.
A thermal conductivity plate is arranged between every two cells of the Micro Blue 7, which is directly connected to the water-cooled structure at the bottom of the battery pack and can achieve active cooling or heating according to the battery working conditions.
The inlet and outlet pipes of the water-cooled structure at the bottom of the battery pack adopt a dual channel serpentine design, which is more conducive to temperature management of the battery module.
Moreover, the battery pack of Buick Micro Blue 7 also uses foam to isolate heat dissipation between battery cells, alleviating the expansion of battery cells during later charging, which can cause safety hazards.
The Micro Blue 6 PHEV battery pack adopts General Motors patented layer by layer liquid cooling technology, with thermal conductivity plates with capillary liquid cooling pipes sandwiched between each two battery cells, with a thickness of only 0.2 millimeters. The flow of coolant in the capillary pipes can accelerate heat conduction.
According to the introduction, the cooling fins of the Micro Blue 6 PHEV battery pack have a temperature adaptation range of -35 ℃ to 55 ℃ for both battery packs.
In terms of materials, the power batteries of the Micro Blue 7 and Micro Blue 6 PHEVs use lightweight composite materials, so the battery pack has a compact and thin shape. The IP67 level sealing design can ensure dust prevention and safe operation of the battery pack when the vehicle is involved in water.
The bottom of the Micro Blue 7 battery pack also features a steel tray design with reinforced ribs to reduce the damage caused by collisions to the battery pack.
In terms of overall body, the Micro Blue 7 adopts a high-performance BFI integrated body structure, with a high-strength steel application ratio of up to 78%, which also greatly protects the safety of the battery pack.
During the full day visit to General Motors China Forward Technology Research Center Battery Laboratory, Lei Fengwang visited two locations in person – General Motors China Forward Technology Research Center Battery Laboratory and SAIC General Motors Power Battery System Development Center Micro Blue 7 and Micro Blue 6 PHEV battery pack production lines.
First, let’s talk about the battery laboratory.
General Motors has independent battery laboratories in both the United States and China, which have established their own battery trial production lines for battery prototype development and various types of testing and certification.
Before each battery is launched on the market, General Motors conducts 3-5 years of battery cell validation and testing in the battery laboratory.
According to staff, General Motors began investing in battery laboratories 10 years ago.
Nowadays, the batteries of the Micro Blue 7 and Micro Blue 6 PHEVs can undergo over 10 types of extreme tests, including compression, collision, soaking, burning, overcharging, over discharging, short circuit, salt spray, etc.
In addition, the battery pack will undergo over a hundred system and vehicle tests covering mechanical, thermodynamic, electrical, lifespan, performance, and other aspects.
The SAIC General Motors Power Battery System Development Center was established in 2015 in Jinqiao, Pudong, Shanghai. It is the second global battery assembly center for General Motors and the first outside of North America.
The new generation modular high-performance ternary lithium-ion battery pack equipped on the Buick Micro Blue 7 and Micro Blue 6 PHEVs at SAIC General Motors Power Battery System Development Center is assembled and produced here.
During the process of cell stacking and battery module assembly, the entire process of loading, assembly, transportation, and battery module testing of cells and modules is intelligently completed by robots or robotic arms, with an automation rate of 100%; Moreover, the accuracy of the robot during each loading/unloading/handling process is within 0.1mm.
According to engineers, there are not many manual inspectors on the entire production line, and they are only responsible for correcting machine malfunctions.
However, these two production lines are not currently busy, and on the afternoon of Lei Feng’s visit, they were even in a “shutdown” state.
Through the application of digital technology, the key components of the Micro Blue 7 and Micro Blue 6 PHEVs not only achieve real-time data collection, monitoring, and early warning during the assembly process, but also have their own “ID cards” through a complete product information traceability system.
For example, the outer packaging of battery cells that have undergone full line error free operation will be printed with a QR code. Only these battery cell products with the QR code can be taken offline. Moreover, scanning the QR code can accurately trace the source of the battery cell, tracing when and where the product passed through the hands of someone.
Another technological highlight is ultrasonic welding.
The engineer explained to us that using ultrasonic technology to weld the electrode ears of battery cells has no fusion welding defects and does not cause high-temperature pollution and damage to semiconductor materials such as aluminum and copper, reducing the risk of electrode ear tearing.
Specifically, ultrasonic pole ear welding is a technology that is accurately positioned by industrial robots under the guidance of a visual system, automatically manipulating the ultrasonic welding head to complete the welding of the positive and negative pole ears of the battery cell, forming a path for the battery module.
In addition, different ultrasonic welding techniques can be used for different materials.
In addition to battery cells, the evaluation of safety testing for modules and battery packs cannot be ignored.
In order to ensure that there are no leakage points in the layer by layer liquid cooled thermal conductive fins of Buick Micro Blue 6 PHEV and the liquid cooled circuit system of Micro Blue 7, the mass flow method will be used for leakage testing in the mold assembly wiring to improve testing accuracy and shorten testing time.
In terms of module welding quality inspection, if there are false or missing welds in the equipment welding, manual welding will be carried out to repair the welding at that point.
As engineers have previously stated, in fact, General Motors is investing far more in new energy.
As early as 1996, General Motors launched the pure electric EV1, which made it a true pioneer in the field of electric vehicles. However, due to the unfavorable timing and immature market environment, General Motors basically gave up on electric vehicles in the following decade.
Although General Motors has started to increase its investment in the research and development of pure electric vehicles in recent years, the NEDC range of the Buick Micro Blue 6, which was released last year, is only 301km. Four months later, General Motors once again launched a new model of the Micro Blue 6 pure electric version, which has also increased its range to 410km. In today’s era where electric vehicles have become mainstream, many new car manufacturers have broken through the 600 km range, The Micro Blue 6 does not have much competitiveness in this regard.
However, General Motors has recently announced the launch of Ultium battery system and third-generation global electric vehicle platform, and Buick Micro Blue 7 and Micro Blue 6 HEVP are also equipped with a new generation of modular ternary lithium battery pack – General Motors has also taken a good step forward.
