The function, role and failure analysis method of battery management system (BMS)

　　The BMS (BATTERY MANAGEMENT SYSTEM) is an important link between the battery and downstream equipment. It can improve the utilization of the battery, prevent the battery from overcharging and over-discharging, extend the battery life, and monitor the battery status.

　　1. The functions and functions or tasks of the battery management system (BMS) can be detailed as follows:

　　1. Protect cells and battery packs from damage;

　　2. Make the battery work in a suitable voltage and temperature range;

　　3. Keep the battery running under proper conditions;

　　4. Battery parameter detection: including total voltage, total current, cell voltage detection, temperature detection, insulation detection, collision detection, impedance detection, smoke detection, etc.;

　　5. Establishment of battery status: including SOC, SOH, SOF.

　　6. Online diagnosis: faults include sensor faults, network faults, battery faults, battery overcharge, over-discharge, overcurrent, insulation faults, etc.;

　　7. Battery safety protection and alarm: When a fault is diagnosed, BMS will report the fault to the system, and cut off the circuit to protect the battery from damage;

　　8. Charge control: slow charge and fast charge control;

　　9. Battery consistency control: Collect cell voltage information, and use equalization methods to make the battery consistent. The equalization methods include dissipative and non-dissipative;

　　10. Thermal management function: During charging and discharging, monitor the temperature of each observation point of the battery pack, and decide whether to turn on heating and cooling;

　　11. Network function: including online calibration and health, online program download. CAN network is usually used;

　　12. Information storage: storage of key data such as SOC, SOH, charge and discharge ampere hours, fault codes, etc.

　　It can be seen that the battery management system is not only closely related to the battery, but also closely related to the upstream and downstream systems. Compared with other products, the battery management system has relatively high failures and is more difficult to deal with.

　　We have summarized some common methods when the battery management system fails, for the reference of relevant personnel.

　　2. BMS failure analysis method

　　1. Observation method: When the system has a communication interruption or a control abnormality, observe whether each module of the system has an alarm and whether there is an alarm icon on the display screen, and then check the phenomenon one by one.

　　When conditions permit, try to reproduce the fault under the same conditions as much as possible to confirm the problem.

　　2. Elimination method: When a similar interference phenomenon occurs in the system, each component in the system should be removed one by one to determine which part has an impact on the system.

　　3. Replacement method: When a certain module has abnormalities in temperature, voltage, control, etc., change the position of the module with the same string number to diagnose the module problem or the wiring harness problem.

　　4. Environmental inspection method: When the system fails, if the system fails to display, we often ignore some details. First of all, we should look at the obvious things: if it is plugged in? Is the switch turned on? Are all the wires connected? Perhaps the root of the problem lies in it.

　　5. Program upgrade method: When an unknown failure occurs after the new program is burned, which results in abnormal system control, the previous version of the program can be burned for comparison to analyze and deal with the failure.

　　6. Data analysis method: When a control or related failure occurs in the BMS, the BMS stored data can be analyzed, and the message content in the CAN bus can be analyzed.

　　Lithium-ion battery (LIB) has become the main energy storage solution in modern social life. Among them, lithium iron phosphate batteries are a perfect substitute for lead-acid batteries, and are the first choice for grid-connected peak shaving, off-grid energy storage, photovoltaic energy storage, UPS, data center and other industries.