Produced by | Tiger sniff car group
Author | Wang Xiaoyu
"450,000 buy Mercedes-Benz, less than a year to change the motor."
Before the Spring Festival, a joint statement of 68 Mercedes-Benz EQC owners circulated on the Internet, and everyone pointed to the same question: "Mercedes-Benz new energy model EQC is suspected of large-scale motor failure." And in the second week of construction a year later, Mercedes-Benz did announce the recall plan:
On February 18, Beijing Benz Automobile Co., Ltd. filed a recall plan with the State Administration for Market Regulation, and from August 15, 2022, recalled some EQC electric vehicles with production dates from November 30, 2018 to December 15, 2021, totaling 10,104 vehicles.
In fact, the Mercedes-Benz EQC, as Mercedes-Benz's first pure electric vehicle SUV model, is not only unfavorable in the Chinese market, but also performs inferiorly in the global electric vehicle market than its competitors BMW and Audi. The German media "Handelsblatt" has reported that Daimler's top management's description of EQC uses a German word "Totales Desaster" – a huge disaster.
In China, tens of thousands of Mercedes-Benz EQC owners are indeed facing a huge disaster.
First, mercedes-benz that does not leak oil, how can it also love bad?
"I thought the quality of Mercedes-Benz would pass, but I didn't expect it to be bronze."
Janie, the owner of the Mercedes-Benz EQC from Guangzhou, chose to go to the 4S store for inspection in November 2021 because the vehicle broke down. After the inspection, the work order given by the 4S shop shows that the motor/power system is not in normal condition. In fact, this problem is not unique, judging from the recall information given by Beijing Benz, involving 10,104 EQC electric vehicles – almost all of the EQC sold in the country, have been recalled.
As Mercedes-Benz's first pure electric vehicle model in the Chinese market, the EQC will be launched on November 8, 2019 and will be produced by Beijing Benz. And 2020 and 2021, equivalent to two full delivery years for EQC. According to the China Association of Automobile Manufacturers, in the whole year of 2020, the cumulative sales volume of EQC was 3863 vehicles. According to the data of the Association, in the whole year of 2021, EQC has accumulated sales of 6098 vehicles. In other words, after the EQC went on sale, it has sold about 9,961 vehicles in the past two years – equivalent to the 10,104 units in this recall.
Here may wish to insert a review, the Xi'an Mercedes-Benz female owner rights protection incident that year, the cause is the engine oil leakage. Today's electric vehicles have completely solved the problem of oil leakage, but a new problem of leakage of coolant has emerged.
In January 2022, 68 EQC owners came together to write a statement about problems related to the failure of high-volume motors.
Among them, they mentioned: after the purchase of Mercedes-Benz EQC, the vehicle has one or more motor failures, and most of them have 1-2 months before the motor failure, the vehicle central control screen will prompt the "fill coolant" style, after opening the front cabin cover, the coolant traces are significantly reduced. Car owners believe that it is the motor failure caused by the penetration of coolant into the motor.
The cause of the failure announced by Beijing Benz in the recall information is basically consistent with the reason speculated by the owners.
It is reported that due to the manufacturing deviation of the electric drive module provided by the supplier, the cooling system in the electric drive module of some vehicles within the scope of this recall may have insufficient sealing, resulting in coolant leakage. If the coolant is slightly infiltrated into the motor, the insulation resistance value of the high-voltage system may be reduced after long-term use, and the vehicle may not start in extreme cases. At the same time, the coolant leakage does not meet the requirements of the relevant national mandatory standards for the sealing of the cooling system, and under extreme conditions, the output power of the electric drive module of the vehicle will be reduced, and there is a safety hazard.
When a fault occurs, the vehicle combination will prompt a corresponding warning message. Extreme conditions may result in a decrease in the output power of the vehicle's electric drive module or the failure of the vehicle to start.
According to the latest data from the China Consumer Quality Complaint Platform, as of December 31, 2021, EQC has been complained about with a total of 27 cases, with a motor failure of up to 24 cases, and the remaining three cases are endurance failure / suspension failure / battery damage.
Compared with Tesla's previous recalls (including the most recent one on February 18), bugs in software functions can be quickly resolved by means of OTA remote upgrades. The problem of the hardware part involved in this Mercedes-Benz, the recall cycle will be quite long. Moreover, the parts involved are not produced in China and need to be imported from overseas. According to the official introduction:
The electric drive modules involved in this recall are manufactured at overseas plants of the relevant suppliers. Affected by various uncertainties in the current overseas market, including the epidemic, the current reserve of the accessory cannot meet the spare parts reserve for the immediate recall. To this end, we are also actively coordinating the supply of spare parts with relevant parts suppliers to ensure that high-efficiency, high-quality recalls are fully launched on time on August 15.
Second, the big run leaks, what is the problem?
These more than 10,000 Mercedes-Benz electric vehicles are planted in the same place - electric drive modules.
More generally speaking, it should be called: "electric drive system", and its importance is equivalent to the engine assembly of fuel vehicles. Electric drive systems generally include electric motors, motor controllers and transmission mechanisms. The most important thing here is the motor, commonly known as the motor. The battery, motor and electronic control constitute the core three electric technology of electric vehicles.
Electric vehicles in the process of driving and recovering energy, the motor stator core, stator windings in the process of movement will produce losses, these losses in the form of heat to divergence, the need for effective cooling medium and cooling methods to take away the heat, to ensure that the motor in a stable cold and heat cycle balance ventilation system safe and reliable operation.
According to the universal characteristic curve of the motor, when the motor is running at a high speed, the efficiency will gradually decrease from about 90% to 80%. Even when the top speed is reached, it is less than 70% efficient. The remaining 30% will be converted into heat.
If the heat control is not good, the light will lead to a decrease in performance, and the heavy will burn the entire motor. Therefore, the design of the motor cooling system will directly affect the safe operation and service life of the motor, but the problem of EQC just happens to lie in the cooling system.
At present, the cooling method on the motor is mainly divided into three types.
One is water-cooled, Mercedes-Benz EQC and Audi e-tron and Porsche Taycan, all of which use water cooling systems to dissipate heat from the motor. The other is oil cooling, such as Huawei's DriveONE all-in-one electric drive system, which uses oil cooling. There is also a kind of air cooling, relying on natural wind blowing, mainly existing in the Hongguang MINI EV, which has a low output power and low heat dissipation requirements, which is ignored here.
The water cooling method is to use layers of materials to transfer the heat inside the motor to the outside, and then be carried away by the waterway. However, there is a temperature gradient from the internal winding of the motor coil to the water-cooled enclosure, and the winding cannot be directly cooled, resulting in temperature accumulation and the formation of local hot spots, so it is necessary to improve the cooling efficiency by directly cooling the heat source.
Water cooling system in audi e-tron motors
However, the oil itself has the characteristics of non-magnetic and non-conductive, does not affect the magnetic circuit of the motor, and can be directly used as the medium for internal cooling. It is possible to go directly inside the motor and the rotor and stator windings of the motor for more complete heat exchange.
Oil-cooled system on Huawei's DriveONE
According to official information, Huawei's electric drive system DriveONE, whose motor stator is all soaked in oil, can directly take away the heat of the windings and core. The rotor oil enters the shaft hole through the specially designed pipe, forms a cooling environment in the shaft to take away the heat of the rotor, and through the spray hole of the outer wall of the rotor, the cooling and heat dissipation of the end of the stator pack is realized, and the heat dissipation effect is better than that of water cooling, and the average peak temperature of the winding is reduced by 30 °C, and the peak temperature of the magnet is reduced by 15 °C.
But then again, both schemes have the potential to leak, but it is only a matter of the degree of destructiveness. For example, in the oil cooling scheme, the severity of the failure consequences of the oil leakage is relatively low (motor heating limit power), while the failure consequences of the cooling water leakage in the water cooling scheme are indeed unacceptable, and the motor high-voltage insulation fails, or even burns out, affecting the safe operation of the vehicle.
Complex cooling system on the Taycan
Either way, the key is for manufacturers and suppliers to do their job well in the design and engineering process. You see the same Ashkenazi pure tram, Audi e-tron and Porsche Taycan are also using water cooling, but the EQC water cooling problem.
Of course, Mercedes-Benz threw the EQC coolant leakage problem to the supplier: "Due to the manufacturing deviation of the electric drive module provided by the supplier", the recall announcement reads.
Third, Mercedes-Benz, long snack bar!
As the pioneering work of Mercedes-Benz in the era of electric vehicles, EQC can be described as a fateful fate.
Because just a few months ago, in November 2021, Mercedes-Benz just conducted a recall overseas, involving 19,000 EQCs. At the time, the official reason for the recall was that the vehicle might have a steering system failure and the driver would receive a red warning message in the gauges. Since the harness of the steering system may have been damaged during assembly, the water in the environment may enter the harness through the isolation layer during the use of the vehicle, and the harness will age or even fail over time.
Looking further ahead, in August 2021, Beijing Benz filed a recall plan with the State Administration for Market Regulation, the reason for the recall is that some EQCs cannot identify and check the status of the air conditioning condensate hose after assembly, and cannot ensure the tightness of its connection, resulting in the air conditioning condensate may enter the crew compartment and corrode the electronic components. At that time, 796 domestic EQCs with production dates from June 12, 2019 to June 18, 2020 were recalled in China.
Perhaps because of the frequent problems in the European and Chinese markets, Mercedes-Benz has repeatedly postponed the entry of EQC into the US market. According to the official Mercedes-Benz US, Mercedes-Benz currently only sells EQS based on the EVA pure electric platform in the United States. EQC, EQA, EQB, pure electric models based on the fuel vehicle platform have not yet had the opportunity to land in the US market.
The electric vehicle category on Mercedes-Benz's official website in the United States does not have EQC in the products on sale
Compared with the cautious situation in the US market, Mercedes-Benz's EQ pure electric series can be described as uninhibited in the Chinese market. In 2022, Mercedes-Benz will have a number of new cars on the market. For example, the aforementioned EQA and EQB two "oil to electricity" models, the luxury pure electric sedan EQS that has just begun to be delivered, and the EQE that has completed the declaration work in the Ministry of Industry and Information Technology.
According to the previous plan, Mercedes-Benz will launch 21 new products in the Chinese market this year, including 8 pure electric and plug-in hybrid models. In the long run, Mercedes-Benz aims to achieve 50% of sales of pure electric and plug-in hybrid models in 2025, and to achieve full electrification in 2030 and only sell pure electric models. In terms of corporate strategy, it will transform from "electric first" to "comprehensive electric".
Of course, the pie of Mercedes-Benz painting is not paid for by Chinese in the end. According to the sales data in 2021, the Chinese market, which sold 758,000 vehicles, accounted for nearly one-third of Mercedes-Benz's total global sales.
Treat the Chinese market, Mercedes-Benz you still have a long snack bar!
Resources:
"Audi e-tron pure electric SUV motor electronic control cooling system"
"There is a big secret hidden in the drive motor!" Water-cooled oil-cooled, is it an increase or a decrease? 》
"A Brief Analysis of Huawei's DriveONE Oil-Cooled Technology: The Key to Overtaking"