CR1625 battery.A brief discussion on why power batteries need a BMS management system?

　　In pure electric vehicles, the power battery pack, as one of the core components, accounts for a very high proportion of the vehicle manufacturing cost, and its performance also directly affects the driving performance and safety of the vehicle. Most of the power batteries used in early pure electric vehicles were lead-acid batteries. Due to their low energy density, short cruising range, and short service life, these batteries were gradually replaced by products such as lithium-ion batteries with outstanding advantages.

　　Currently, the new energy vehicles being vigorously developed are mainly divided into three categories: hybrid electric vehicles (Hybrid Electric Vehicle, HEV), fuel cell vehicles (Fuel Cell Electric Vehicle, FCEV) and pure electric vehicles (Electric Vehicle, EV). These three types of electric vehicles have different characteristics with their own different structures and working principles, and are also at different stages of development. Pure electric vehicles use on-board power battery packs (such as lithium-ion batteries, lead-acid batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, etc.) as their only energy source and are equipped with high-power motors to drive the vehicle. Therefore, they are different from traditional internal combustion engine vehicles. The biggest difference is the unique electric drive and control system of pure electric vehicles. Compared with hybrid electric vehicles, pure electric vehicles have low noise, no pollution, zero emissions, and a simpler chassis structure; compared with fuel cell vehicles, all aspects of technology are relatively more mature and have higher reliability and safety. Therefore, pure electric vehicles have attracted great attention from governments and car companies around the world. Many companies have achieved mass production and started demonstration operations in some areas.

　　In pure electric vehicles, the power battery pack, as one of the core components, accounts for a very high proportion of the vehicle manufacturing cost, and its performance also directly affects the driving performance and safety of the vehicle. Most of the power batteries used in early pure electric vehicles were lead-acid batteries. Due to their low energy density, short cruising range, and short service life, these batteries were gradually replaced by products such as lithium-ion batteries with outstanding advantages. Lithium-ion batteries have attracted the attention and use of many electric vehicle manufacturers at home and abroad due to their advantages such as high charge and discharge efficiency, high energy density and long endurance.

　　Although lithium batteries have more advantages than other types of batteries, they are also limited by factors such as cell materials and current manufacturing processes. As a result, there are often differences in internal resistance, capacity, voltage, etc. between single-cell lithium batteries. Therefore, In practical applications, individual cells within the battery pack are prone to uneven heat dissipation or excessive charging and discharging. Over time, these batteries in poor working condition are likely to be damaged in advance, and the overall life of the battery pack will be greatly shortened. Not only that, there is a risk of explosion when the battery is in a severely overcharged state, causing damage to the battery pack and posing a threat to the user's life safety. Therefore, the power battery pack on electric vehicles must be equipped with a targeted battery management system (Battery Management System, BMS) to effectively monitor, protect, energy balance and fault alarms for the battery pack, thereby improving the entire power battery pack. work efficiency and service life.

　　As the monitoring and management center of the pure electric vehicle power battery pack, the battery management system must conduct real-time and dynamic monitoring of the temperature, voltage, charge and discharge current and other related parameters of the battery pack. When necessary, it can proactively take emergency measures to protect each single battery and prevent The battery pack is subject to dangers such as overcharging, over-discharging, overheating, and short circuit. In addition, the system must also accurately estimate the SOC of the battery throughout the battery pack's life cycle, and promptly feed back key information such as remaining power, driving range, and fault abnormalities to the driver in an appropriate manner, and at the same time, in a Complete the data exchange function between the system and the vehicle ECU or host computer in a suitable way.

　　However, these are the functions and performances that BMS can achieve under optimal design and ideal conditions. As far as the current overall performance of related BMS products from various electric vehicle accidents related to power batteries or actual applications to cars are concerned, It can be seen from the performance that the functions of the currently widely used battery management systems are not perfect enough, the technology is not mature enough, the scope of use is limited, and the versatility is not strong. Specifically, it can be summarized into the following five aspects:

　　①The battery management system is not accurate enough in collecting relevant parameters of the power battery pack under long-term use.

　　②The battery management system cannot fully realize the accurate estimation of the SOC value of the power battery pack throughout its life cycle.

　　③The control effect of energy balance between individual cells within the battery pack needs to be further improved.

　　④The battery management system’s fault self-diagnosis and self-maintenance functions for itself and the battery pack are not yet complete enough.

　　⑤The current battery management system products are generally targeted, have limited scope of use, and are not portable and versatile enough.

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