These three types of electric vehicles, with their different structures and operating principles, possess distinct characteristics and are at different stages of development. Pure electric vehicles (EVs) rely solely on onboard battery packs (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 technologies are 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 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.
Although lithium batteries offer numerous advantages over other types of batteries, 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 batteries. Therefore, in practical applications, uneven heat dissipation or overcharging/discharging can easily occur among the individual cells within the battery pack. Over time, these batteries operating under suboptimal conditions are likely to fail prematurely, significantly shortening the overall lifespan of the battery pack. Furthermore, severely overcharged batteries pose a risk of explosion, damaging the battery pack and endangering the user's safety. Therefore, it is essential to equip electric vehicle 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 battery pack.
As the monitoring and management center of the power battery pack in pure electric vehicles, the battery management system must dynamically monitor relevant parameters such as battery temperature, voltage, and charging/discharging current in real time. When necessary, it must proactively take emergency measures to protect individual battery cells and prevent dangers such as overcharging, over-discharging, overheating, and short circuits. Furthermore, the system must accurately estimate the battery's State of Charge (SOC) throughout its entire lifespan and promptly relay key information such as remaining charge, driving range, and fault anomalies to the driver. It must also facilitate data exchange between the system and the vehicle's ECU or host computer in a suitable manner.
However, these are functions and performance characteristics that can only be achieved under optimal design and ideal conditions. Based on current performance data from various electric vehicle accidents related to power 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. Specifically, this can be summarized in the following five aspects:
① The battery management system does not collect relevant parameters of the power battery pack accurately enough under long-term use.
② The battery management system cannot yet fully realize the accurate estimation of the SOC value of the power battery pack throughout its entire life cycle.
③ The control effect on 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.
