Analysis of 12 common failure types in battery management system (BMS)
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2022/06/21 10:36:12
Among all the faults, BMS faults are relatively high and difficult to deal with compared to other systems.
The Battery Management System (BMS) controls Battery charging and discharging and estimates Battery status. It is closely related to the Battery and the vehicle System.
However, many domestic automobile manufacturers and battery PACK companies are not aware of the importance of BMS. Some car companies even think that by linking individual battery cells together, they can keep the car running and take chances on its safety.
Some automakers (such as low-speed cars) are known to pursue low prices in BMS procurement in order to gain market share. In order to get the contract, some bad BMS suppliers reduce the BMS function index or "castrate" some functions to achieve the effect of low cost.
But in fact, among all the failures, compared with other systems, BMS failures are relatively high and more difficult to deal with. So irresponsible, in the safety hidden danger, while the benign development of the industry caused damage.
Therefore, qidian lithium big data reporters on the type of common BMS failure analysis, sorted out for reference in the industry.
1. The main relay does not close after power-on
Possible causes:
The load detection line is not connected, the precharging relay is open, and the precharging resistance is open.
Troubleshooting:
Use the BDU display module to check the bus voltage data, check the battery bus voltage, load bus voltage is normal; Check whether the load bus voltage rises during precharging.
2. BMS cannot communicate with ECU
Possible causes:
The BMU does not work or the CAN signal cable is disconnected
Troubleshooting:
Check whether the 12V/24V power supply of the BMU is normal. Check whether the CAN signal transmission line is out of pin or plug is not inserted; Monitor CAN port data to see whether BMS or ECU packets CAN be received.
3. The communication between BMS and ECU is unstable
Possible causes:
The external CAN bus does not match well and the bus branch is too long
troubleshooting
Check whether the bus matching resistance is correct; Whether the matching position is correct and whether the branch is too long.
4. BMS internal communication is unstable
Possible causes:
The communications cable plug is loose, the CAN cable is not standardized, and the BSU address is repeated.
Troubleshooting:
Check whether the wiring is loose; Check whether the bus matching resistance is correct, the matching position is correct, whether the branch is too long; Check whether the BSU address is the same.
5. The whole system does not work after the system is powered
Possible causes:
The power supply is abnormal, the wiring harness is short-circuited or disconnected, and the DCDC has no voltage output.
Troubleshooting:
Check whether the power supply from the external power supply to the management system is normal and reaches the minimum operating voltage required by the management system. Check whether the limited current setting of the external power supply causes insufficient power supply to the management system. External power supply can be adjusted to meet the power requirements of the management system; Check whether the cable harness of the management system is short-circuited or disconnected, and modify the cable harness to make it work normally. If the external power supply and cable harness are normal, check whether the DCDC that supplies power to the entire system in the management system has voltage output. If an exception occurs, replace the faulty DCDC module.
6. Battery current data is incorrect
Possible causes:
The hall signal cable plug is loose, the Hall sensor is damaged or connected incorrectly, and the collection module is damaged.
Troubleshooting:
Re plug the current Hall sensor signal line; Check whether hall sensor power supply is normal, signal output is normal; Replace the collection module.
7. Battery temperature difference is too large
Possible causes:
The cooling fan plug is loose, the cooling fan is faulty, the coolant fails, and the cold zone system is not started.
Troubleshooting:
Reinsert the fan plug cable. Power the fan separately, check whether the fan works properly, replace the coolant, and check the cooling system.
8. Error is reported after relay operation
Possible causes:
Relay auxiliary contact disconnects, and relay contact sticks
Troubleshooting:
Re-plug and unplug the wiring harness; Use a multimeter to measure whether the on-off state of the auxiliary contact is correct, and then replace the relay after the fault of fusing is eliminated.
9. Do not use a charger to charge
Possible causes:
The communication between the charger and BMS is abnormal
Troubleshooting:
Replace a charger or BMS to confirm BMS or charger failure; Check whether the matching resistance of the BMS charging port is normal.
10. Vehicle instrument has no BMS data display
Possible causes:
The cable harness connection of the main control module is abnormal
Troubleshooting:
Check whether the wiring harness of the main control module is fully connected, whether there is normal low-voltage working voltage of the vehicle, and whether the module works normally
11. Detection data of some battery boxes is lost
Possible causes:
Some connectors of the vehicle may be in bad contact, or the BMS slave control module cannot work properly
Troubleshooting:
Check the contact of connectors, or replace the BMS module; .
12. SOC is abnormal
Phenomenon: SOC varies greatly in the working process of the system, or jumps repeatedly between several values; In the charging and discharging process of the system, the SOC has great deviation. SOC displays constant values all the time.
Possible causes:
Current is not calibrated; The current sensor model does not match the host program; The battery is not deeply charged and discharged for a long time; Data acquisition module acquisition jump, leading to SOC automatic calibration; Hall sensor failure;
Two conditions of SOC calibration are: 1) overcharge protection is achieved; 2) The average voltage is above xxV. Customer battery consistency is poor, overcharge, the second condition cannot be achieved. View the remaining capacity and total capacity of the battery through the display. The current sensor is not connected correctly.
Troubleshooting:
Calibrate the current in the touch screen configuration page; Change the host program or replace the current sensor;
Conduct a deep charge and discharge of the battery; Replace the data acquisition module, manually calibrate the system SOC, and suggest the customer to do deep charge and discharge once a week; Modify the host program and adjust xxV in the condition of "average voltage above xxV" according to the actual situation of customers. Setting the correct total capacity and remaining capacity of the battery; Connect the current sensor correctly to make it work normally.
Conclusion:
It is reported that BMS is an indispensable component in power and energy storage battery packs. With the development of the new energy industry chain, THE technology and market size of BMS are growing rapidly.
In terms of technology, starting Point Research (SPIR) statistics show that in 2017, BMS cost accounted for 20% of the total battery pack cost on average, but in 2018, with the rapid development of technology, it has been reduced to more than 15%, accounting for about 6% of the vehicle cost.
Related personnel of a management system manufacturer said that in the past, there were insulation detection alarm, acquisition module data is 0, and so on, now less occurrence.
Now, the rapid development of BMS technology, in insulation detection, there is basically no alarm related to the problem; At the same time, the case that the data of the acquisition module is 0 is also very rare.
In terms of market, Starting Point Research (SPIR) predicts that the compound annual growth rate of global BMS market brought by new energy vehicles will reach about 30% from 2018 to 2025.
This shows that the development of the market is mixed, except for some good and unhealthy phenomenon, BMS technology development and the size of the market has made a qualitative leap, and progress.
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