Safety Analysis of New Energy Vehicle Battery Monitoring System

At present, many domestic battery manufacturers have insufficient understanding of the importance of BMS, thinking that as long as each single cell core can be linked, it can guarantee the operation of the vehicle, and it is lucky to be safe, and pursue low prices in BMS procurement. In order to sign the contract, BMS suppliers only have to reduce certain indicators and functions, which also leaves hidden dangers for battery failure.

Since the spontaneous combustion of Hangzhou Zhongtai pure electric taxi and Shanghai 825 electric bus, consumers have mentioned the unprecedented safety of new energy vehicles.

On the day before the deadline, the reporter visited the Yaojiayuan Dongfang Jiye Automobile Market, the largest automobile trading market in Beijing's East Fifth Ring Road, and conducted a questionnaire survey on “Guiding Factors Affecting Consumers' Purchasing New Energy Vehicles” and interviewed 50 new pairs. Potential customers who understand or care about energy vehicles. The results of the survey were surprising: about 90% of the population identified the primary concern as safety, not the price factor previously envisaged; 80% knew or probably knew about the spontaneous combustion event that occurred above.

On August 18, the four ministries and commissions including the Ministry of Science and Technology, the Ministry of Finance, the Ministry of Industry and Information Technology and the National Development and Reform Commission jointly issued a “Safety Order” for the demonstration and promotion of new energy vehicles (the “Letter on Strengthening the Safety Management of Energy Saving and New Energy Vehicles Demonstration and Promotion”). Emphasize that “the plug-in hybrid vehicle and pure electric vehicle that are put into demonstration operation must be equipped with real-time monitoring system (BMS) for vehicle operation technology status, especially to strengthen the monitoring of the working status of power battery and fuel cell”.

According to industry insiders, this notice will put the safety of new energy vehicles on the right track and re-establish the public's confidence in new energy vehicles. However, Han Jingke, general manager of Shanghai Boqiang Microelectronics Co., Ltd. believes that BMS is as important as the quality of the power battery pack and plays a vital role in avoiding battery burning.

The root cause of spontaneous combustion is the battery?

Since the occurrence of the spontaneous combustion incident, the public has questioned the safety of new energy vehicles, which directly affects the public's confidence in the consumption of new energy vehicles.

On June 8, the Hangzhou Municipal Government reported the identification results of “the battery failed to meet the needs of the vehicle environment, and the battery leakage, insulation damage and partial short circuit occurred”.

After the results were announced, an industry expert who did not want to be named analyzed the reporter. There are several possibilities for self-ignition of the power battery: first, the problem of the battery itself, problems with the materials and production processes; secondly, the monitoring system appears after the battery is grouped. The problem is that it does not play its due function; again it is the problem of the plug-in system, the resistance at the interface is too large, causing a short circuit. Of course, there may be problems with electrical circuits. As far as the use of the car is concerned for several months, the possibility of the latter two problems is very low.

"At present, the production level of domestic single cells is not much different from that of the international market. However, the consistency of battery after grouping is very different. Many manufacturers still stay in the manual production stage, which makes it difficult to ensure the consistency of battery groups." Lanke Electric Vehicle Technology Co., Ltd. Ma Wei told reporters.

Zeng Lingpeng, deputy general manager of Chery New Energy Automobile Co., Ltd., said that despite the current status of domestic battery group-related standards, although the national unified power battery group testing standard has not yet been introduced, some enterprises according to their own situation, including technology path, technology research and development level Different, they also form different versions of the enterprise standards, these enterprise standards will be further improved with the continuous maturity of technology.

The monitoring system is not a "life-saving grass"

Some insiders said that the installation of BMS can effectively improve the utilization of the battery, prevent overcharging and overdischarging of the battery, and prolong the service life of the battery, monitor the operating status of the battery pack and each battery core, and make an emergency to the driver in advance. Early warning, to win time for security.

However, according to a survey by the reporter, the BMS system was installed in the Wanxiang Power Battery Pack produced by Wanxiang Group (Industrial) Co., Ltd. before the self-ignition of Hangzhou Zhongtai Pure Electric Taxi.

Han Jingke pointed out that BMS is as important as the quality of the power battery pack and plays a vital role in avoiding battery burning.

Prince Dong gave an example for the reporter to emphasize the importance of the two: "Currently, the results of the single-cell, small-module battery test and the results after the group are very different. The single-cell battery meets the safety and performance standards, which does not mean The performance and safety of the group are guaranteed. In terms of safety, life and discharge capacity, the single battery can be charged and discharged 2000 times, and may only be 1000 times after being grouped. If there is no mature BMS, the battery will be caused. The local power consumption of the core is too large, and local heat is generated, and the information cannot be transmitted to the driver, which is easy to cause spontaneous combustion of the battery. This aspect indicates that the battery grouping technology needs to be improved, and on the other hand, the importance of BMS for group operation. ”

“The power battery is assembled into the whole vehicle in groups. The quality of the battery, whether the safety can be guaranteed, whether the performance is stable, etc., need to be fed back through the BMS,” he said. However, the BMS system can only be used as a fault monitor for battery pack operation. Yang Zhiwei, general manager of Taiwan Likai Energy Technology Co., Ltd., told reporters that the BMS real-time monitoring system has the function of transmitting the battery pack fault signal to the driver and the dashboard, but in the high-speed driving, even if it is found in time, if there is no professional knowledge. The consequences are still difficult to imagine. Only when the battery quality is excellent, BMS can realize the safety of the power battery.

Monitoring system itself

"Because of the lack of basic technical parameters and standards for BMS in China, there is no authority to test the BMS produced by the manufacturer, so it is difficult to guarantee the quality and large-scale promotion." Han Jingke said.

He also pointed out that at present many battery manufacturers in China do not have enough understanding of the importance of BMS, thinking that as long as each individual battery core can be linked, it can guarantee the operation of the vehicle, and it is lucky to be safe in BMS procurement. Pursue low prices. In order to sign the contract, the BMS supplier only reduces certain indicators and functions.

When discussing whether China's battery technology is synchronizing with foreign countries, some industry experts believe that battery group testing has the biggest gap with foreign countries.

Yang Zhiwei agreed with this: "At present, most domestic BMS are still in the market pattern of their own battles. There are dozens of companies doing BMS, but there are only a few developed countries in Europe and America, and the degree of specialization is relatively high." Yang Zhiwei told reporters. At present, in the field of BMS systems, the international core competitiveness is mainly concentrated in the US listed companies such as Texas Instruments, O2Micro, and Linear Technology. Domestic battery suppliers basically adopt BMS developed by themselves. Compared with the former, the system has lower price, but the stability and safety are poor. It mainly supplies domestic battery group enterprises.

"Zhongtai electric car spontaneous combustion incident is not accidental, which is exposing the current domestic imperfections in the design, testing and standards of pure electric vehicle power battery group." An industry insider said sharply.

“Battery grouping is by no means a simple superposition of single cells, involving many complicated technologies. The testing and testing of battery group design is very necessary, and a set of standards is needed to evaluate the basic performance and safety of battery grouping. "Prince Dong said.

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