The implementation of mandatory national standards is the key to improving battery safety

In recent years, the production and sales of electric bicycles in mainland China have grown rapidly. According to statistics, the current social ownership of electric bicycles in China has exceeded 350 million, and the output of electric bicycles by enterprises above designated size in the country will be 42.28 million in 2023. With the increase in the production and sales of electric bicycles year by year, the fire accidents caused by them have also increased year by year, causing serious losses to the personal and property safety of consumers.

Why do e-bikes catch fire? According to the statistical analysis of the fire and rescue department, there are three main reasons for the fire of electric bicycles: one is the thermal runaway fire of the lithium battery used in the electric bicycle, the second is the overload and short circuit of the electric bicycle, and the third is the fire of the electric bicycle charger. Among them, lithium batteries accounted for the largest proportion of fires.

There are two main types of batteries used in electric bicycles: lead-acid batteries and lithium batteries, and the proportion of lithium batteries has gradually increased in recent years, and the proportion of lead-acid batteries has gradually decreased. Lead-acid batteries use an inorganic electrolyte system (concentrated sulfuric acid), so they will not catch fire or explode. Due to the shortcomings of low energy density and poor endurance at low temperatures, lead-acid batteries are mainly used in low-end models. Previously, lithium battery models accounted for only about 10%, but in recent years, the proportion of new models released by major domestic electric bicycle brands equipped with lithium batteries has gradually increased, and it is now close to 30%. Lithium batteries use organic electrolyte systems (such as ethylene carbonate solvents), which are easy to decompose into flammable gases such as carbon monoxide, hydrogen, and methane under high temperature and overcharge, and are easy to catch fire and explode when encountering oxygen in the air. Lithium batteries with defective design, flawed manufacturing process, poor material stability, and long use are more likely to decompose combustible gases. For high-nickel ternary materials (nickel-cobalt-manganese, nickel-cobalt-aluminum, etc.), they will also decompose oxygen, which can burn and explode without external oxygen. This is also the reason why the safety of high-nickel ternary lithium batteries is worse.

Electric bicycle lithium battery safety standards. Article 10 of the Standardization Law of the People's Republic of China stipulates that "mandatory national standards shall be formulated for technical requirements for ensuring personal health and life and property safety, national security, ecological and environmental safety, and meeting the basic needs of economic and social management." "Lithium batteries for e-bikes pose a safety risk and have caused a large number of accidents, so mandatory national standards need to be developed.

According to statistics, the supply of the top 9 lithium batteries for electric bicycles accounts for about 40% of the total market, the supply of more than 100 small enterprises accounts for about 30%, and the supply of modified batteries for small workshops accounts for about 30%. Many of the assembled batteries supplied by small workshops are used in automobile dismantling and recycling, and the unqualified batteries eliminated by enterprises, and the design of battery protection circuits is not perfect, and a considerable proportion of accidents are caused by assembled and modified batteries.

According to rough estimates, lithium manganese oxide batteries account for about 60%, high-nickel ternary lithium batteries account for about 30%, and lithium ferrous phosphate batteries account for less than 10%. In general, from the perspective of safety, lithium ferrous phosphate batteries> lithium manganese oxide batteries> high-nickel ternary lithium batteries; However, from the perspective of performance indicators such as low temperature capacity and battery life, lithium ferrous phosphate batteries< lithium manganese oxide batteries < high-nickel ternary lithium batteries. Therefore, enterprises and consumers choose different types of lithium batteries, often according to their own needs from performance, safety, price and other aspects of a relatively balanced choice. When formulating strong safety standards for lithium batteries for electric bicycles, we first need to consider the safety characteristics of different types of lithium batteries, put safety indicators in the first place, and also consider the balance between the development of industry and technology and safety. In addition, it is necessary to set a threshold from the technical point of view to prevent the assembly and modification of batteries in small workshops and the entry of waste and eliminated batteries into the field of electric bicycles.

The recently released "Safety Technical Specifications for Lithium-ion Batteries for Electric Bicycles" stipulates 6 test items for single batteries and 22 test items for battery packs. Overcharge and acupuncture tests can effectively screen the safety of lithium batteries, such as the current low safety of high nickel ternary batteries is difficult to pass the above tests, while better safety of lithium ferrous phosphate batteries, lithium manganese oxide batteries through the relevant tests is relatively easy. In addition, the standard also stipulates the requirements for the traceability of the high temperature resistance of the battery pack, mutual recognition and collaborative charging, and the prohibition of the use of cascade batteries.

Ensuring the implementation of strong safety standards is the key. Standards are the technical basis for follow-up supervision, but the formulation of standards is only the first step to improve safety supervision. The key to improving the safety level of e-bike batteries is to truly implement the implementation of strong standards.

For the compliance verification of the standard, there are two main ways: one is post-supervision, which does not require the compliance of the standard to be proved in advance before production and sales, but verifies the compliance of the standard through the later market supervision and spot checks; The other is pre-supervision, which requires products to prove compliance with standards before being sold through compulsory certification and other means. The relevant departments are considering studying the inclusion of lithium-ion batteries for electric bicycles in the compulsory certification (CCC certification) catalogue management. In addition, the use management of lithium batteries for electric bicycles after sales also needs to be put in place. For the illegal assembly and modification of "black workshops", the illegal use of waste batteries, and the unauthorized modification and use of illegal batteries by users, it is necessary for public security, traffic management and other departments to investigate and identify in strict accordance with the standards, and increase law enforcement.

How can consumers use e-bikes safely? One is to buy electric bicycles that have passed the relevant certification from regular channels, use original batteries, do not modify or replace them yourself, if you need to repair or replace, you need to go to a regular after-sales service site. The second is to use the original charger and regular charging cabinet to charge the battery to avoid overcharging caused by mismatched charging voltage. Third, when not in use for a long time, the battery should neither be in an empty state nor in a fully charged state. Fourth, avoid charging the battery in extremely low temperature conditions in winter, and avoid parking electric bicycles or charging batteries in a sunny environment in summer. Fifth, for old batteries that have been used for many years, especially those that have been bulging, leaking, and heating, they should be replaced in time.

Safety is both the threshold and the bottom line. Only by keeping the bottom line of safety can we seek development. Safety standards are the basis for regulating the development of the industry and the basis for industry supervision. Although it is important to formulate mandatory national standards for e-bike battery safety, it is even more critical to truly implement the implementation of the standards.