At present, the vigorously developed new energy vehicles are mainly divided into three categories: Hybrid Electric Vehicle (HEV), Fuel Cell Electric Vehicle (FCEV), and Pure Electric Vehicle (Electric Vehicle, EV). These three types of electric vehicles have different characteristics and are also in different development stages due to their other structures and working principles. Pure electric cars use on-board power battery packs (such as lithium-ion batteries, lead-acid batteries, nickel-hydrogen batteries, nickel-cadmium batteries, etc.) as their only energy source. They are equipped with high-power motors to drive the car. Therefore, it is different from traditional internal combustion engine vehicles. The most significant difference is the electric drive and control system unique to pure electric vehicles. Compared with hybrid electric vehicles, pure electric cars have low noise, no pollution, zero emissions, and have a more straightforward chassis structure; compared with fuel cell vehicles, all aspects of technology are relatively more mature, with higher reliability and safety. Therefore, pure electric cars have been highly valued by governments and car companies worldwide, and many companies have achieved batch processing and started demonstration operations in some regions.
In pure electric vehicles, the power lithium battery pack, as one of the core components, occupies a very high proportion of the manufacturing cost of the whole car, and its performance also directly affects the driving performance and safety of the entire vehicle. Most of the power lithium batteries used in early pure electric cars were lead-acid batteries. Due to their low energy density, short cruising range, and short service life, these batteries were gradually replaced with 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 benefits, such as high charging and discharging efficiency, high energy density, and muscular endurance.
Although lithium-ion batteries have more advantages than other batteries, they are also limited by cell materials and current manufacturing processes, resulting in differences in internal resistance, capacity, and the voltage between single-cell lithium-ion batteries. Therefore, the single cells inside the battery pack are prone to uneven heat dissipation or excessive charge and discharge in actual use. Over time, these batteries in poor working conditions are likely to be damaged in advance, and the overall life of the battery pack will be significantly shortened. The battery is in a serious overcharged state, and there is a danger of explosion, causing damage to the battery pack and a threat to the safety of the user's life. Therefore, it is necessary to equip the power lithium battery pack on electric vehicles with a set of the targeted battery management system (battery Management System, BMS) to effectively monitor, protect, balance the energy and alarm the failure of the battery pack, thereby improving the overall power lithium battery The working efficiency and service life of the battery pack.
As the monitoring and management center of pure electric vehicle power lithium battery packs, the battery management system has to monitor the temperature, voltage, charge and discharge current, and other related parameters of the battery pack in real-time and dynamically and can take emergency measures to protect every single battery when necessary. Be alert to the dangers of overcharge, over-discharge, overheating and short circuit of the battery pack. In addition, the system also has to accurately estimate the SOC of the battery during the entire service cycle of the battery pack and timely feed back key information such as remaining power, driving range, and abnormal faults to the driver in an appropriate manner, and at the same time in a proper way. A suitable way to complete the data exchange function between the system and the vehicle ECU or host computer.
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