These three types of electric vehicles, with their different structures and operating principles, have developed distinct characteristics and are at different stages of development. Pure electric vehicles (EVs) rely solely on an onboard battery pack (such as lithium-ion, lead-acid, nickel-metal hydride, and nickel-cadmium batteries) as their energy source and are powered by a high-power electric motor. Therefore, the biggest difference between EVs and traditional internal combustion engine vehicles lies in their unique electric drive and control system. Compared to hybrid electric vehicles, EVs are quieter, pollution-free, and have zero emissions, with a simpler chassis structure. Compared to fuel cell vehicles, their technology is more mature, offering higher reliability and safety. Consequently, EVs have received significant attention from governments and automakers worldwide, with many companies already achieving mass production and beginning demonstration operations in certain regions.
In pure electric vehicles, the power lithium battery pack, as one of the core components, accounts for a very high proportion of the overall vehicle manufacturing cost, and its performance directly affects the vehicle's driving performance and safety. Early pure electric vehicles mostly used lead-acid batteries, which, due to their low energy density, short driving range, and relatively short lifespan, were gradually replaced by superior products such as lithium-ion batteries. Lithium-ion batteries, with their high charging and discharging efficiency, high energy density, and long driving range, have attracted the attention and use of many electric vehicle manufacturers both domestically and internationally.
While lithium-ion batteries offer numerous advantages over other battery types, they are still limited by factors such as cell materials and current manufacturing processes. This leads to variations in internal resistance, capacity, and voltage between individual lithium-ion cells, making uneven heat dissipation and overcharging/discharging common issues within the battery pack during actual use. Over time, these batteries operating under suboptimal conditions are likely to fail prematurely, significantly shortening the overall lifespan of the battery pack. Furthermore, severe overcharging poses a risk of explosion, damaging the battery pack and endangering the user's safety. Therefore, it is essential to equip electric vehicle lithium-ion battery packs with a targeted Battery Management System (bMS) to effectively monitor, protect, balance energy, and provide fault alarms, thereby improving the overall efficiency and lifespan of the power lithium-ion battery pack.
As the monitoring and management center of the lithium-ion battery pack in pure electric vehicles, the battery management system must dynamically monitor relevant parameters such as temperature, voltage, and charging/discharging current of the battery pack in real time. When necessary, it must proactively take emergency measures to protect individual battery cells, preventing dangers such as overcharging, over-discharging, overheating, and short circuits. Furthermore, the system must accurately estimate the battery's State of Charge (SOC) throughout the entire battery pack's lifespan and promptly relay key information such as remaining charge, driving range, and fault anomalies to the driver in an appropriate manner. Simultaneously, it must facilitate data exchange between the system and the vehicle's ECU or host computer in a suitable way.
However, these are functions and performance characteristics that a battery management system (bMS) can only achieve under optimal design and ideal conditions. Based on current performance data from various electric vehicle accidents related to lithium-ion batteries and the overall performance of bMS products actually used in automobiles, it is clear that the functions of currently widely used battery management systems are not yet perfect, the technology is not mature enough, the scope of application is limited, and the versatility is weak. This can be summarized in the following five aspects:
① The battery management system does not collect relevant parameters of the power lithium battery pack with sufficient accuracy under long-term use.
② The battery management system cannot yet fully realize the accurate estimation of the SOC value of the power lithium battery pack throughout its entire life cycle.
③ The control effect of energy balance among individual cells within the battery pack needs further improvement.
④ The battery management system's self-diagnosis and self-maintenance functions for itself and the battery pack are not yet perfect.
⑤ Currently available battery management system products are generally targeted, have limited application scope, and lack sufficient portability and versatility.
