1. Battery protection, similar to PCM, overcharge, overdischarge, over temperature, over current, and short circuit protection. Like ordinary lithium manganese batteries and ternary lithium batteries, once the voltage of any battery exceeds 4.2V or the voltage of any battery is lower than 3.0V, the system will automatically cut off the charging or discharging circuit. If the battery temperature exceeds the battery operating temperature or the current is greater than the battery discharge current, the system will automatically cut off the current path to ensure the safety of the battery and the system.

　　2. Energy balance, the entire battery pack, because many batteries are connected in series, after a certain period of work, due to the inconsistency of the battery cell itself, the inconsistency of the working temperature and other reasons, it will eventually show a big difference, which will affect the battery. The life of the battery and the use of the system have a huge impact. Energy balance is to make up for the differences between individual battery cells to do some active or passive charging or discharging management to ensure the consistency of the battery and extend the life of the battery.

　　There are generally two types of passive balancing and active balancing in the industry. Passive balancing is mainly to balance the power with more power through resistance consumption, and active balancing is mainly to transfer the power of the battery with more power to the less power through capacitor, inductance or transformer. The battery reaches equilibrium.

　　Because the active equilibrium system is relatively complex and the cost is relatively high, the mainstream is still passive equilibrium.

　　3. SOC calculation, battery power calculation is a very important part of BMS, many systems need to know the remaining power situation more accurately. Due to the development of technology, many methods have been accumulated for SOC calculation. The remaining power can be judged according to the battery voltage if the accuracy is not high. The main accurate method is the current integration method (also called Ah method), Q=∫idt, and Internal resistance method, neural network method, Kalman filter method, etc. The mainstream in the industry is still the current scoring method.

　　4. Communication, different systems have different requirements for communication interfaces. The mainstream communication interfaces include SPI, I2C, CAN, RS485, etc. Among them, the automobile and energy storage systems are mainly CAN and RS485.

　　Due to insufficient competition in the BMS system and the complexity of the system, there are relatively few system manufacturers. The related chip manufacturers are mainly European and American manufacturers, and there are a few large domestic companies in the research and development. There are many opportunities in the future. (Let’s talk about the analysis of the failure of the protection board below)