The lithium battery is mainly composed of two blocks, the battery cell and the BMS. The battery cell is equivalent to the heart of the lithium battery, and the BMS is equivalent to the brain of the lithium battery.

　　BMS - Battery Management System, is a system for managing lithium batteries. It usually has the functions of measuring battery voltage, current, temperature, etc., to prevent or avoid abnormal conditions such as over-discharge, over-charge, and over-temperature of lithium batteries. The specific functions are as follows:

　　1. BMS has over-charge, over-discharge, over-temperature, over-current, and short-circuit protection. Like a lithium iron phosphate battery, once it detects that the voltage of any battery exceeds 3.90V or the voltage of any battery is lower than 2.0V, 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. BMS can perform a certain energy balance on the cells. Due to the inconsistency of the cell itself, the inconsistency of the operating temperature and other reasons, different cells will eventually show great differences. Energy balance is to make up for the differences between individual batteries to do some active or passive charge or discharge management to ensure the consistency of the battery and extend the life of the battery.

　　3. SoC calculation is a very important part of BMS, and many systems need to know the remaining power situation more accurately. There are many methods accumulated in the calculation of SoC. If the accuracy is not high, the remaining power can be judged according to the battery voltage. The main accurate method is the current integration method (also called the Ah method), Q = ∫i dt, and the internal resistance method. Neural network method, Kalman filter method, etc. The mainstream in the industry is still the current scoring method.

　　4. BMS can design different communication interfaces according to the needs of customers. Mainstream communication interfaces include SPI, I2C, CAN, RS485, etc. Among them, the automobile and energy storage systems are mainly CAN and RS485.