What causes the thermal runaway of new energy batteries?

The first is that the battery is overheated. As I just said, the battery will only run out of control when it is hot. There are various reasons for overheating. It may be that the temperature of the battery pack itself is uneven, and the temperature in some areas is high. Short circuit, internal short circuit, etc. These electrical reasons will emit heat, as well as mechanical reasons, such as water ingress, poor sealing, collisions, and so on. Let's take a look at the main reasons for these recent accidents. We think it is a product quality problem. Product quality problems refer to products that fail to strictly abide by relevant technical standards and specifications in the process of design, manufacturing, verification, and use. There are three important categories. First, there is insufficient detection and verification of battery products; second, the reliability of the vehicle changes during use; third, there is a problem with the charging safety management technology. Let's break down these aspects. First, there is insufficient detection and verification of battery products. Since the policy cycle of subsidy retreat is once a year, it does not match the product development cycle as a whole. For example, the improvement of our chemical material system generally takes more than one year, but because the company follows the subsidy guidance rod, blindly The pursuit of high specific energy shortens the time for detection and verification. Sometimes in order to shorten the development cycle, physical improvements are often preferred, such as thickening the battery active material and thinning the diaphragm, so that the specific energy of the battery will increase, but the safety performance will decrease. The second is that the detection and verification methods for electric batteries are not perfect and cannot reflect the actual vehicle usage conditions. A large number of companies have not established internal battery safety detection standards, and some companies do not even have the ability to detect battery safety. The quality is also uneven. The third reason is that the reliability of the vehicle is reduced during the aging process. For example, the waterproof effect of the whole life cycle is not good. Generally, the sealing of our battery must pass the IP67 standard, but when the vehicle is used for a long time, the sealing will become worse, causing water to enter the vehicle, which will easily cause a short circuit. For example, in the laser welded joints of batteries, voids are prone to appear in the welded joints. These voids will increase the impedance, and then generate high temperature points and cause thermal runaway. There is also the aging of the battery system and the high-voltage electrical appliances of the charger. For example, the contactor when we charge is often broken, and sometimes it will arc, causing this kind of burn or adhesion on the surface of the high-temperature flexible contactor, which will short-circuit and heat up. These are the reasons for thermal runaway. The fourth reason is charging. The data communication during charging is not standardized. BMS manufacturers and charger manufacturers do not strictly implement the newly issued national standards. The charging function is safe. According to reason, our battery management system has a good power-off function for charging. When charging is controlled by the battery management system, we currently do not strictly implement the functional safety specifications, which is ISO26262. This norm has not been fully implemented at present, and this is also the reason why we have not abided by the norm. Relevant standards for charging safety are not strictly enforced. For example, the adhesion of our charging relays should have a diagnostic function, but some do not in order to save costs. The battery management system and the charging pile are not equipped with qualified insulation test devices, and the charging circuit formed by the vehicle and the charging pile does not meet the standard requirements of insulation voltage, creepage distance, overload, IP rating, plugging force, locking, temperature rise, and lightning strike BMS did not strictly abide by the regulations of charging guidance. Why is it a quality problem? That is, we did not strictly abide by the standards and regulations in all aspects of design, manufacturing, use, and verification. Of course, we also lack some. For example, our annual safety inspection is lacking, but this is not the company’s business, this is the government’s Things to do. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Current status and development prospects of the lithium battery industry