New energy vehicle safety issues

"China new energy vehicle promotion and application experience exchange and development seminar" held grandly on November 25-27 in Shenzhen Ping Shan New Area.

The following is the speech by wang fang, chief expert of China automotive technology research center and director of new energy department:

The safety problem of new energy vehicles is very important. On the one hand, the safety problem of electric vehicles will cause damage to personnel; on the other hand, it will cause property loss; on the third hand, it will cause damage to the train brand; on the fourth hand, it will cause damage to the electric vehicle industry. The safety of electric vehicles covers manufacturing, transportation, storage, use, maintenance and scrapping in a broad sense.

The normal use safety of electric vehicles includes two aspects: first, the high-voltage safety under the use of the whole vehicle. Includes safety issues in the event of wading or being caught in the rain during normal use. On the one hand is the destruction of the environment, the other is the external electromagnetic impact of electric vehicles safety.

High voltage safety, including protection level, power balance, insulation withstand voltage and other parameters, must ensure that these parameters will not harm the human body. On the one hand, it includes the use of electric cars; on the other hand, it also includes charging, including quick charging. During charging, the radiation of the battery will not cause harm to human body. The center now focuses on this area of research.

In terms of the safety of charging, there are two main ways of charging current, namely, alternating current and direct current (ac) and wireless charging. Ac charging involves ac devices, vehicle-mounted batteries and management systems, and dc charging dc charger and management system. Security issues involve four aspects:

First, the safety of charging system components.

Second, the safety requirements of the battery system.

Third, the security requirements of communication interaction.

Fourth, operational safety regulatory requirements.

The relevant standards for safety-related charging include:

First, grid-side charging facility requirements.

Second, charging interface communication.

Third, the standard of vehicle charging management system.

Electric cars are essentially battery packs and battery systems. Further extending to the outside is the monitoring center of the charging station and the vehicle monitoring center. Now there are more monitoring centers of battery packs for battery enterprises, which must have safety requirements for these links. In addition, for the safety of charging components, enterprises need to check the product safety requirements against the released standard 20234 version 2011. The most notable is the temperature rise overrun. The main aspect is that the battery pack has a certain degree of overcharge resistance. If the overcharge resistance is not good, there is a great risk to rely on the management system completely. In addition, the management system must have corresponding protection.

The requirements of the GBT2793 communication protocol make detailed provisions on the safety of communication. For the side of the charger and the detailed fault requirements of the charging car BMI side, there are a series of message provisions.

Certain measures must be taken for the monitoring of charging stations and vehicle monitoring.

In terms of collision safety, vehicle testing is conducted according to the first three standards, and the same requirements are also applied to traditional vehicles. Now, national standard 31498 adds some regulations on electric safety to the requirements for collision safety of electric vehicles. The test of electric vehicle collision, mainly focused on electrical safety and battery protection and occupant protection, fire and explosion is the most worthwhile thing to test.

The center has done more than 200 collisions of new energy vehicles, but in terms of electric vehicles, most of those that passed the test were low-speed electric vehicles. What is related to the battery is the deformation caused by the unreasonable position. In addition, the battery is not safe enough to meet the requirements, and the insulation resistance is too low to be qualified.

Emergency rescue safety, now is also very important. The cnac center has done a lot of experiments and has given some guidance on fire hazards and emergency rescue in the future. Unlike conventional cars emergency workers need to have professional knowledge.

There are several kinds of accidents:

First, collision.

Second, liquid leakage.

Third, fire.

Fourth, water.

On the one hand, the battery system standard is the battery itself, which should have basic requirements for its mechanical safety, electrical safety and environmental safety. In the meantime, should have the protective function such as overcharge, overput, overheat. The enclosure of the battery pack must have a protective rating and performance requirements, as well as an anti-impact strength requirement. The battery system is required to guarantee both safety and reliability. Two new standards have been issued this year. Although these two standards are not mandatory, many enterprises use this standard for safety assessment.

On the other hand, the heat of the battery is out of control. During the use of the battery, there will be a series of reactions, including heat of reaction and heat of polarization, which will eventually lead to the possible causes of the heat loss control, as well as some leakage of cars or liquids. Under different battery SOZ, T3 and T5 have different points of thermal runaway. The higher the battery is, the easier it is to have thermal runaway. When the heat gets out of control to the temperature point, it only takes a few seconds for it to spread to the battery, and good insulation is needed to keep the heat from spreading.

For battery pack testing, the testing organization does a lot, but the operation is very irregular. Battery pack is a high-voltage system, there are a lot of security risks, the test should pay attention to safety, before the test must be communication, electrical safety for detailed detection, and then start all the battery pack evaluation.

In terms of mechanical-related evaluation, vibration and battery mechanical simulation collision and extrusion, the strength and anti-extrusion performance of the battery shell are worthy of our attention. In addition, the prevention and control of the battery itself and the anti-seawater immersion ability of the battery pack itself are also worthy of our attention.

Because of the battery material system and process design, we hope to ensure the safety of the battery itself. Secondly, we hope to further improve the safety of the battery through module packaging. Finally, BMS, relays, fuses and battery boxes are assembled to improve the reliability and safety of the system.

On the hidden trouble investigation, need to do a good job in the new vehicle hidden trouble investigation method. Whether the newly produced vehicles can meet the requirements of the new standards. In addition, the consistency of the product needs to be guaranteed.

It is expected that the major enterprises will be concerned about the greening of batteries, the aging of vehicle speed limit, and whether the safety protection functions are complete. There are not too many requirements for the battery protection function, and we hope to upgrade the existing vehicles. In addition, also hope that the major enterprises for battery safety inspection, including hardware and software consistency, chlorination of the battery and line aging. For the battery charging and use should have what fault function troubleshooting can meet the corresponding requirements.

Conclusion:

First, electric vehicle and battery safety is the first element.

Second, you should choose a suitable battery for different models.

Thirdly, the supervision in the operation of electric vehicles, including the supervision on one side of vehicles, the supervision on the side of charging piles and the supervision on urban operation, should be analyzed and processed in a timely manner.

Fourth, each enterprise and the local government carries on the prompt hidden danger elimination inspection, in particular large quantities on the vehicle.

The page contains the contents of the machine translation.