How the BMS lithium-ion battery protection board works

The reason why Lithium Battery should be protected is determined by their own characteristics. Since the material of the Lithium Batteries itself determines that it cannot be overcharged, over-discharged, over-current, short-circuited and charged and discharged at ultra-high temperature, the Li-ion battery component will always be followed by a delicate protection plate and a current safety device.

The bMS protection function of Li-ion batteries is usually completed by the protection board and PTC and other current devices. The protection board consists of electronic circuits that accurately monitor the battery voltage and charge/discharge circuit current at -40°C to +85°C, and timely control the on/off of the current circuit. PTC prevents serious battery damage in high temperature environments.

A standard LiFePO4 Battery protection board usually includes control ICs, MOS switches, resistors, capacitors and auxiliary devices such as FUSE, PTC, NTC, ID, memory, etc. Among them, the control IC controls the MOS switch under normal conditions so that the cell and the external circuit are connected, and when the cell voltage or circuit current exceeds the specified value, it immediately controls the MOS switch off to protect the safety of the cell.

BMS Lithium Iron Phosphate Battery protection function description:

1. Battery protection, similar to PCM, over charge, over discharge, over temperature, over current and short circuit protection.

2. Energy balance, the whole lithium-ion battery pack, due to many batteries in series, after working according to time, due to the inconsistency of the battery itself, the inconsistency of the working temperature and other reasons, it will eventually show a big difference, which has a huge impact on the life of the battery and the use of the system. Energy balance is to compensate for the differences between individual cells 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, due to the development of technology, SOC calculation accumulated a lot of methods, the accuracy requirements are not high, can judge the remaining power according to the battery voltage, the main accurate method is the current integration method (also known as Ah method), Q=idt, as well as internal resistance method, neural network method, Kalman filter method.

4. Communication, different systems have different requirements for communication interfaces, and the mainstream communication interfaces are SPI, I2C, CAN, RS485 and so on. Among them, the important automotive and energy storage systems are CAN and RS485.

Battery balancing: This is the balanced charging of each lithium-ion battery so that each battery in the battery pack reaches a balanced and consistent state. Balancing technology is a key technology of battery energy management system that is being researched and developed in the world.