Can future 18650 battery 3500mah lithium management systems provide early warning before accidents occur?

　　This is a mandatory standard for the safety requirements of power batteries for electric vehicles that the Ministry of Industry and Information Technology posted online for opinions on the 10th. I will not go into details about the 18650 battery 3500mah lithium system requirements in this standard. There are 15 items. The 18650 battery 3500mah lithium standards currently being implemented are relatively large. The difference is that one is the vibration test. I made the vibration road spectrum requirements based on the actual road spectrum collection. In addition, the requirement for water immersion requires that after vibration, it must undergo a certain state of use before doing the water immersion test. Another very, very important thing is the thermal diffusion test. It is assumed that thermal runaway of a 18650 battery 3500mah lithium is definitely possible, and the probability of occurrence will always exist. Although we hope to reduce this probability as low as possible, in fact it must be existing. What we require in this case, as I just said, is that we are more concerned about the occurrence of internal short circuit, so we must first simulate the internal short circuit in different ways, and then when this kind of thermal diffusion and thermal runaway occur, When a 18650 battery 3500mah lithium undergoes thermal runaway, we define the conditions under which the thermal runaway occurs, including its temperature rise rate, maximum temperature value, and voltage drop.

　　After this happens, we have to see its subsequent reaction. First of all, if there is no alarm signal for such an accident, that is to say, electric vehicles are now required to be equipped with such a thermal runaway accident alarm signal. If there is not, or if the entire 18650 battery 3500mah lithium catches fire within 5 minutes after the accident alarm signal occurs, we will Consider it ineffective and the product does not meet the requirements. In the other two forms, if this kind of thermal runaway occurs again after 5 minutes, the entire 18650 battery 3500mah lithium pack is stuck, and we also recognize it as safe, or in the end, the entire 18650 battery 3500mah lithium pack is not stuck, which is the best state. Why? Our basis is that the occupants can be given enough escape time within 5 minutes, or how long it takes, because the most basic concept of electric vehicle safety is personnel safety, and other things are not considered. . So as long as there is enough time for people to escape, we consider it safe. Therefore, it is acceptable to have a fire or no fire within 5 minutes.

　　But in fact, this is our current draft of the GB standard. When we write it into global regulations, there will still be some problems. For example, I have listed the problems in the following six major points:

　　The first point is the various experiences you just mentioned. For example, if solid-state batteries develop in the future, or even batteries that really don’t catch fire, this is of course our OK state. So what should we decide in the current situation? What are the conditions for exemption we need to determine, that is, what are the conditions for not doing thermal diffusion? Is the energy density value lower than a certain value, or what type of 18650 battery 3500mah lithium can do without it? This is what we have to do.

　　The second point is high repeatability and reproducibility. Because in fact, the methods we use now, such as using heating or acupuncture to cause thermal runaway in the 18650 battery 3500mah lithium, you will add heat to it from the outside world, and this will affect the results of the 18650 battery 3500mah lithium experiment. Its reproducibility, so this is what we need to study on reproducibility.

　　The third point is that we also need to choose the point that triggers thermal runaway.

　　The fourth point is the reproducibility of the entire system of thermal runaway.

　　The fifth point is safe escape time. In fact, the 5 minutes we set before was based on our fire drills in the past two years. In fact, everyone will also point out that the escape times of two different types of vehicles, passenger cars and commercial vehicles, are different, and we need to do more. research and determination.

　　Point six, different ingredients and levels of safety. This is related to the out-of-control evaluation we just mentioned. We also have a dedicated domestic team studying it, which is its toxic gas analysis, toxicological hazard level analysis and fire level analysis. We are also the topic of the second phase, and we are also doing a It is equivalent to a small advertisement, because the second phase is being carried out from 2018 to the end of 2020. There are four topics in it, thermal diffusion, vibration, seawater immersion, and toxic gas analysis. These four are basically proposed by our Chinese experts. I was also entrusted as the leader of the Chinese technical team for the second phase. Now we have established special domestic research groups for our four proposals. If you have experience in this area, I hope you can give more support to the work of our industry. This is also part of China's participation in global regulations.

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