Battery defects and improper use are the main causes of electric vehicle safety accidents

What is the reason for the frequent accidents of electric cars? How can electric cars break local protection? At present, the domestic electric vehicle safety problems are mainly reflected in the use of batteries, material composition and charging safety. Imbalanced development of upstream and downstream industries and blind weight of enterprises are the main factors that cause these safety problems. In addition, there are loopholes in supervision and control, and government related policies are also one of the reasons.

Therefore, the electric vehicle related enterprises must strictly grasp the quality link, carry out technological innovation, strengthen supervision and control, and can not make rash progress; The relevant government departments should also pay attention to the safety of electric vehicles, gradually improve relevant policies and regulations, ensure coordination and cooperation among various departments, and promote the orderly, healthy and stable development of the electric vehicle industry.

Analyzing safety accidents in electric vehicles: battery defects and improper use are the main causes

1, electric car safety accident cause

From 2011 to 2015, a total of 24 fire accidents occurred in new energy vehicles in China, including 15 pure electric passenger cars, 5 hybrid passenger cars, and 4 pure electric passenger vehicles. In these 24 accidents, it was either a spontaneous combustion accident, a collision accident, or a charging accident. For the analysis of these accidents, the causes of these accidents are mainly the following:

(1) Improper use of batteries

During the use of the battery, there will be a short circuit in the case of liquid soaking, damage to the diaphragm, and damage to the insulation, causing the battery to overheat and catch fire. As the usage time increases, the battery will gradually age, resulting in changes in various parameters and increased unsafe factors. In addition, some low-quality electric cores have problems such as burrs, dislocation, impurities, and pollution, which can lead to short circuits and accidents in the use of power cells.

(2) The battery material does not pass

At present, most electric vehicles in our country use lithium batteries as the main raw material for power batteries. Due to the active and flammable chemical properties of lithium ions, collisions and extrusion during actual use will cause damage to the battery pack, exposing lithium ions in the cell to the air and causing fire.

In addition, due to the low degree of mechanization of the installation and assembly of batteries in our country, the production of individual cells or batteries is not consistent and the quality is uneven, and cell leakage occurs from time to time. Once the electrolyte comes into contact with oxygen, it will quickly decompose and burn the battery pack, causing a safety accident.

(3) Deficiencies in the power battery system

Some battery throat hoops (connectors of soft hard tubes) are in the wrong position, which can easily cause battery coolant leakage, causing the battery to overheat and catch fire;

Some batteries have unreasonable internal high voltage accessories and line layout, which can easily cause short circuit after being squeezed;

Some battery systems have poor protection design and poor anti-squeezing ability. Once they are squeezed, they will be deformed, the casing will be broken, the internal bracket will be damaged, the connectors will be loose, and the high and low voltage harnesses will wear, which will cause safety hazards.

(4) Charging causes a fire

There are many electric vehicle fire accidents in our country, some of which are caused by electric vehicle overcharge. Because the charging station is not overcharged, it causes a fire during the charging process. Many charging piles are installed in underground garages or large parking lots. An electric car fire may ignite other vehicles around it, causing unpredictable losses. At low temperature, charging without preheating measures leads to a higher temperature field difference, which is also one of the reasons for charging safety accidents.

Problems exposed in safety accidents of electric vehicles

According to the investigation and analysis of the causes of electric vehicle safety accidents, some problems in the development of electric vehicles have gradually emerged. These problems have become the main factors that restrict the safe, orderly, stable and long-term development of electric vehicles. Specifically, there are the following points:

(1) The weight of the production link is light

From 2013 to 2015, the number of qualified vehicles produced in China reached 497,000, which has entered a period of rapid development. This has also brought pressure on the supporting battery industry. Battery manufacturers often ignore the quality in the production process in order to ensure the supply. Requirements.

In addition to parts and components other than batteries, there are also cases of non-compliance with national standards and requirements. Although the country has added many safety requirements to the revision of relevant standards for electric vehicles, including temperature monitoring devices, mechanical locks, electronic locks, etc., there are still some parts and components products that can not meet the standards. With recharging guns, for example, few manufacturers are currently able to provide standard products.

In addition, the communication protocol during the charging process has the situation that the interrupt charging instruction fails and continues to charge; Battery management systems (BMS) also appear to send erroneous signals and commands to charging facilities. For example, charging instructions are also issued after the battery is full, eventually causing overcharging protection failure, resulting in charging accidents.

In terms of charging piles, with the influx of a large number of charging facilities, there have been uneven product quality. Some charging piles failed to meet the National standards when they were assembled. These charging piles are prone to leakage and overflow. There are certain safety hazards.

(2) Power cell technology needs to be improved and innovated

According to data from the testing agency, the risks of monomer batteries in existing power battery systems are widespread. Low risks include leakage, deformation, and exhaust. High risks include sparks and explosions. If the heat of the monomer battery is out of control, the spark and fire of the ternary material is much larger than that of the lithium iron phosphate material. This is not only a problem that has occurred in the accident, but also a potential safety hazard.

On the other hand, the overall design of the battery system lacks rationality, there is no unified planning for the design space of each component, and the probability of accident risk is very high. According to the survey, the top 10 domestic manufacturers in the field of new energy parts and components systems do not have uniform standards and requirements for the gap between battery modules and battery packs, and they are in high-voltage electrical components such as plugs and cables. There is also a lack of reasonable and unified planning for the safety protection of the entire system such as the motor controller.

(3) The monitoring system is a formality

In some areas, electric vehicle surveillance systems do not play a true role in monitoring security. They are more used as data acquisition tools than as early warning and error reporting of system safety. Some surveillance systems are even used as exhibits during visits. It loses its proper role and is only a matter of form.

For electric vehicles, the early warning of accidents is very important, which is even more prominent in the application of buses. Unlike the strict risk control measures of passenger vehicles, the manufacturing of buses is separate, and the manufacturing of batteries and vehicles is different from each other. They each fight and lack complete monitoring capabilities.

(4) There are problems in the design of the whole vehicle system

In terms of vehicle design, there is a lack of planning for batteries and in-vehicle space, and there is insufficient protection for the entire vehicle. Once the battery catches fire, there is too little evacuation time for the personnel in the vehicle and the chances of escape become low. This is more obvious in the safety accident of pure electric buses, and there are more problems.

(5) Inadequate measures taken by government departments to strengthen safety

It is well known that China has relevant requirements and implementation standards for motor vehicle security inspection. In terms of fuel vehicles, there are related security requirements for fuel consumption and displacement, but security checks for electric vehicles do not include electric drive power systems related to safety. The lack of security leads to the inability of the government to monitor and detect the power safety of electric vehicles and related issues.

(6) Lack of training of professional knowledge

In the infrastructure construction of electric vehicles, a large number of employees lack professional knowledge related to electric vehicles. Taking a Sino-German automobile project as an example, the construction workers who installed the charging piles and even several farmers did not have the professional knowledge related to electric vehicles. The charging piles installed were not only not standardized, but also had major problems in safety. In the whole vehicle sales, there is no professional training and information for consumers on the safety knowledge of electric vehicles.

Improve the safety of electric cars recommendations

Safety is the basis for the development of new energy vehicles. From the particularity of electric vehicle power system, the interactivity of infrastructure and the practical experience in market application, it is urgent to strengthen the safety of electric vehicle and reduce the hidden danger in every link.

(1) to maintain market rationality and improve quality

In recent years, the development of electric vehicles in China has achieved good results, but at the same time we can not ignore the safety problem. Enterprises should remain calm in the face of good policies. They should not blindly carry out quantitative expansion and production capacity expansion, and relax on security issues and technical issues. Once the quality control management and other aspects of relaxation, coupled with insufficient technical maturity, will accelerate the expansion of the problem.

Therefore, no matter whether it is a complete vehicle, parts or infrastructure, it must not be blindly built. Relevant enterprises should pay great attention to product quality and safety issues, strictly implement national standards, conduct safety tests, and promptly recall and rectify products that occur in safety accidents. On the other hand, the government should formulate and improve relevant assessment standards, so that product quality standards can be referenced, and strictly conduct certification and testing, and standardize the management of the safety of new energy vehicles.

Particular attention needs to be paid to the construction of charging facilities. As the electric car catches fire when charging, it will cause a serial effect. A car fire is likely to cause extensive losses. In the event of a major accident, the development of the entire electric car industry is fatal. Therefore, the construction and safety of electric charging piles in large parking lots and underground garages should be cautious.

(2) Attaching importance to technological innovation and promoting product iteration

In the existing battery technology, it is not only necessary to strengthen the safety of the battery itself, that is, the safety brought by the electrochemical characteristics of the core itself, but also to strengthen the protective function of the battery management system and strengthen the safety test of the battery. In addition, due to the characteristics of electric vehicles, the battery has a long service life and a large number of charge and discharge times. In battery design and safety testing, the safety of the battery's full life cycle scope must be considered to avoid related safety accidents due to battery aging.

In the research and development of new battery technology, we must focus mainly on technology. Can not blindly increase the energy density of the existing battery, the higher the energy density of the battery, the future problems are likely to be the same as the atomic bomb, small size and damage. Therefore, we must take into account the energy density and safety, and carry out research and development on the basis of ensuring safety. In the process of research and development, it is not only concerned about whether the product can pass the safety inspection and related standards, but should pay attention to how to design the product and maximize battery safety. On the other hand, governments and companies need to invest in long-term funding, technology, and time for the development of more secure new-generation batteries and even the development of all-solid batteries, and ensure the safety of electric vehicles through the updating of iterative products.

(3) Strengthening Supervision and Establishing a Monitoring System

At present, the supervision of the whole vehicle factory in the traditional automotive field is relatively sound. Although there are many items of supervision in the new energy field, it is not specific enough and sufficient. In the process of supervision, it is not only for a certain link, but also for the system supervision of vehicle management and control.

For parts and charging facilities, as the use time increases, there will be aging equipment and parts damage in the future, and the safety hazards caused by long-term charging will further increase, especially in the case of safety accidents during charging, which will have a wider impact. Therefore, supervision of the safety of charging facilities is extremely necessary.

With regard to the safety of electric vehicles, an integrated prevention and control system should be established to prevent the main and multi-level linkage. All aspects of the electric vehicle industry and all aspects of the monitoring chain to achieve "detection, early warning, control" to achieve real-time, effective, multi-level linkage of the systematic system of prevention and control, prevention and control system should play a role, can not be reduced to form.

(4) Government departments should strengthen coordination and improve relevant policies

The development of electric vehicles is dominated by four ministries and commissions. At the same time, it involves many government departments and systems such as residential construction, energy, and electricity. In strengthening the safety of electric vehicles, various government departments are also required to cooperate and improve relevant standards and supervision issues. For government departments, it is necessary to send special personnel or specialized departments to systematically understand and study the safety problems of electric vehicles.

In security inspection, the power system is an important part of the safety of electric vehicles, and it is also extremely necessary to improve the relevant security inspection measures of electric vehicles. In addition, the safety of electric vehicles should be systematically discussed, and feedback and reports should be formed, which will attract the attention of relevant departments; In future exchanges, we should strengthen the links with government departments and adopt policy norms to ensure the orderly, safe and stable development of the electric vehicle industry.

(5) to attach importance to personnel training and handling emergency measures

In personnel training, we should strengthen the knowledge reserve and professional qualification of employees in the electric vehicle industry in our country, draw on the successful experience of domestic and foreign companies, carry out systematic training and qualification of relevant personnel, and be allowed to take up the post after approval. On the other hand, it is necessary to strengthen popular science propaganda at the market level, provide special guidance to crew members and the public on the safety of electric vehicles, produce safety manuals, and strengthen the popularization of safety knowledge and awareness.

In the design of the vehicle, especially the design of large passenger cars, the isolation of passengers and batteries must be reasonably designed. Once the battery is caught in fire, the fire will be controlled in the battery box or the combustion speed will be delayed to ensure that the passengers in the vehicle have sufficient time to escape; The fire extinguishing device must also be installed. In the event of a fire, it can quickly control or slow down the spread of the fire.

In addition, it is also possible to follow the experience of foreign countries, introduce insurance mechanisms, negotiate and cooperate with domestic insurance companies, and minimize losses after the accident and obtain certain guarantees.

The page contains the contents of the machine translation.