Working principle and protection function of BMS lithium-ion battery protection board
Working principle of BMS lithium-ion battery protection board:
The reason why lithium-ion batteries need to be protected is determined by their own characteristics. Because the material of the lithium-ion battery itself determines that it cannot be overcharged, over-discharged, over-current, short-circuited, and ultra-high temperature charging and discharging, the lithium-ion battery components will always appear with a delicate protection board and a current fuse.
The BMS protection function of lithium-ion batteries is usually completed by a protection circuit board and current devices such as PTC. The protection board is composed of electronic circuits, which can accurately monitor the voltage and charge and discharge of the battery cell at all times in an environment of -40°C to +85°C The current of the loop can be switched on and off in time to control the current loop; PTC prevents severe damage to the battery in a high temperature environment.
Ordinary lithium ion battery BMS protection board usually includes control IC, MOS switch, resistor, capacitor and auxiliary devices FUSE, PTC, NTC, ID, memory, etc. Among them, the control IC controls the MOS switch to turn on under all normal conditions to make the cell and the external circuit conduct, and when the cell voltage or loop current exceeds the specified value, it immediately controls the MOS switch to turn off to protect the cell’s Safety.
BMS lithium-ion battery protection function introduction:
1. Battery protection, similar to PCM, overcharge, overdischarge, overtemperature, overcurrent, and short circuit protection.
2. Energy balance, the entire lithium-ion battery pack, because many batteries are connected in series, after working for a certain time, due to the inconsistency of the battery cell itself, the inconsistency of the working temperature and other reasons, it will finally show a big difference , Has a huge impact on battery life and system usage. Energy balance is to make up for the differences between individual battery cells to do some active or passive charge or discharge management to ensure battery consistency and extend battery life.
3. SOC calculation. Due to the development of technology, there are many methods for SOC calculation. If the accuracy is not high, the remaining power can be judged based on the battery voltage. The most important accurate method is the current integration method (also called Ah method), Q= ∫idt, there are internal resistance method, neural network method, Kalman filter method and so on.
4. Communication. Different systems have different requirements for communication interfaces. The mainstream communication interfaces include SPI, I2C, CAN, RS485, etc. Among them, CAN and RS485 are important for automobiles and energy storage systems.
5. Balance between batteries: that is, the single lithium-ion battery is balanced and charged, so that each battery in the battery pack reaches a balanced state. Equalization technology is the key technology of a battery energy management system that is currently being researched and developed in the world.