September 22, 2023
Working principle of BMS lithium-ion battery protection board:
The reason why lithium-ion batteries need to be protected is determined by its own characteristics. Since the material of the lithium-ion battery itself determines that it cannot be overcharged, over-discharged, over-current, short-circuited, or charged and discharged at ultra-high temperatures, 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 and can accurately monitor the voltage and charge and discharge of the battery core at all times in an environment of -40°C to +85°C. The current of the loop can be controlled in time to make the current loop on and off; PTC can prevent severe damage to the battery in high temperature environments.
Ordinary lithium-ion battery bMS protection boards usually include control IC, MOS switches, resistors, capacitors and auxiliary devices FUSE, PTC, NTC, ID, memory, etc. Among them, the control IC controls the MOS switch to turn on when everything is normal, so that the battery core is connected to the external circuit. When the battery core voltage or loop current exceeds the specified value, it immediately controls the MOS switch to turn off to protect the battery core. Safety.
Introduction to BMS lithium-ion battery protection functions:
1. Battery protection is similar to PCM, including overcharge, over-discharge, over-temperature, over-current, and short-circuit protection.
2. Energy balance. Since many batteries are connected in series, the entire lithium-ion battery pack will eventually show a big difference after working for a while due to the inconsistency of the cells themselves, the inconsistency of the operating temperature and other reasons. , has a huge impact on the life of the battery and the use of the system. Energy balancing is to make up for the differences between individual cells and perform 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. Due to the development of technology, many methods have been accumulated 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, as well as internal resistance method, neural network method, Kalman filter method, etc.
4. Communication. Different systems have different requirements for communication interfaces. The mainstream communication interfaces include SPI, I2C, CAN, RS485, etc. Among them, automotive and energy storage systems are mainly CAN and RS485.
⒌Balance between batteries: It is to charge the single lithium-ion battery equally so that each battery in the battery pack reaches a balanced and consistent state. Balance technology is a key technology of battery energy management system that the world is currently researching and developing.