The editor summarizes some common methods when dealing with battery management system failures and case analysis of common failures of battery management system, for reference by relevant personnel of vehicle, battery, and management system manufacturers.

　　The battery management system (BATTERYMANAGEMENTSYSTEM), commonly known as battery nanny or battery housekeeper, is an important link between on-board power batteries and electric vehicles. Its main functions include: real-time monitoring of battery physical parameters; battery state estimation; online diagnosis and early warning; charging, discharging and Pre-charge control; balance management and thermal management, etc. The battery management system (BMS) is mainly to improve the utilization of the battery, prevent the battery from overcharging and overdischarging, prolong the service life of the battery, and monitor the status of the battery.

　　The battery management system is not only closely related to the battery, but also has various connections with the vehicle system. Among all the faults, the battery management system is relatively high compared to other systems, and it is also more difficult to deal with. The editor summarizes some common methods when dealing with battery management system failures and case analysis of common failures of battery management system, for reference by relevant personnel of vehicle, battery, and management system manufacturers.

　　BMS failure analysis method

　　Observation

　　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.

　　failure reproduction method

　　The failures of vehicles under different conditions are different. If conditions permit, try to reproduce the failures under the same conditions as much as possible to confirm the problem.

　　Exclusion

　　When similar interference occurs in the system, each component in the system should be removed one by one to determine which part is affecting the system.

　　substitution method

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

　　Environmental Inspection Law

　　When the system fails, such as the system cannot be displayed, we should not rush to carry out in-depth consideration, because often we will 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.

　　program upgrade method

　　When an unknown fault 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 fault.

　　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.

　　Common failure case analysis

　　1. 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 external power supply to the management system is normal, whether it can reach the minimum operating voltage required by the management system, and whether the external power supply is set to limit current, resulting in insufficient power supply to the management system; the external power supply can be adjusted to meet the requirements of the management system Electricity requirements; check whether the harness of the management system is short-circuited or open, modify the harness to make it work normally; if the external power supply and harness are normal, check whether the DCDC powering the entire system in the management system has a voltage output; if so If abnormal, the bad DCDC module can be replaced.

　　2, BMS cannot communicate with ECU

　　Possible Causes

　　BMU (main control module) is not working, CAN signal line is disconnected

　　Troubleshooting

　　Check whether the 12V/24V power supply of the BMU is normal; check whether the CAN signal transmission line is withdrawn or the plug is not plugged in; monitor the CAN port data and whether the BMS or ECU data packet can be received.

　　3, BMS and ECU communication is unstable

　　Possible Causes

　　The external CAN bus is poorly matched, 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 communication line plug is loose, the CAN wiring is not standardized, and the BSU address is duplicated.

　　Troubleshooting

　　Check whether the wiring is loose; check whether the bus matching resistance is correct, whether the matching position is correct, and whether the branch is too long; check whether the BSU address is duplicated.

　　5, insulation detection alarm

　　Possible Causes

　　Leakage of battery or drive. , The detection line of the insulation module is connected incorrectly.

　　Troubleshooting

　　Use the BDU display module to check the insulation test data, check the battery bus voltage, whether the negative bus voltage to ground is normal; use the insulation shaker to measure the insulation resistance of the bus and the driver to the ground.

　　6. The main relay does not close after power-on

　　Possible Causes

　　The load detection line is not connected, the pre-charge relay is open, and the pre-charge resistor is open.

　　Troubleshooting

　　Use the BDU display module to check the bus voltage data, check the battery bus voltage, whether the load bus voltage is normal; check whether the load bus voltage rises during the pre-charging process.

　　7, the acquisition module data is 0

　　Possible Causes

　　The collection line of the collection module is disconnected, and the collection module is damaged.

　　Troubleshooting

　　Re-plug the module wiring, measure whether the battery voltage is normal at the collection line connector, and measure the resistance at the temperature sensor line plug.

　　8. Battery current data error

　　Possible Causes

　　The Hall signal cable plug is loose, the Hall sensor is damaged, and the acquisition module is damaged.

　　Troubleshooting

　　Re-plug and plug the signal wire of the current Hall sensor; check whether the power supply of the Hall sensor is normal and whether the signal output is normal; replace the acquisition module.

　　9, the battery temperature difference is too large

　　Possible Causes

　　The cooling fan plug is loose, and the cooling fan is faulty.

　　Troubleshooting

　　Reconnect the fan plug wire; power the fan separately and check whether the fan is normal.

　　10, the battery temperature is too high or too low

　　Possible Causes

　　The cooling fan plug is loose, the cooling fan is faulty, and the temperature probe is damaged.

　　Troubleshooting

　　Re-plug the fan plug; power the fan separately and check whether the fan is normal; check whether the actual temperature of the battery is too high or too low; measure the internal resistance of the temperature probe.

　　11, the system reports an error after the relay operates

　　Possible Causes

　　Relay auxiliary contacts are broken, and relay contacts are sticking

　　Troubleshooting

　　Re-plug the wiring harness; use a multimeter to measure whether the auxiliary contact is on or off correctly.

　　12. Cannot use charger to charge

　　Possible Causes

　　The communication between the charger and the BMS is abnormal

　　Troubleshooting

　　Replace a charger or BMS to confirm whether the BMS is faulty or the charger is faulty; check whether the matching resistance of the BMS charging port is normal.

　　13. There is no BMS data display on the vehicle instrument

　　Possible Causes

　　The main control module wiring harness connection is abnormal

　　Troubleshooting

　　Check whether the main control module wiring harness is fully connected, whether there is a normal low-voltage working voltage for the car, and whether the module is working properly

　　14. The detection data of some battery boxes is lost

　　Possible Causes

　　Some connectors of the whole vehicle may be in poor contact, or the BMS slave control module may not work normally

　　Troubleshooting

　　Check the contact of the connector, or replace the BMS module;.

　　15, SOC abnormal

　　Phenomenon: SOC changes greatly during the working process of the system, or repeatedly jumps between several values; during the charging and discharging process of the system, the SOC has a large deviation; the SOC always shows a fixed value.

　　Possible Causes

　　The current is not calibrated; the current sensor model does not match the host program; the battery has not been deeply charged and discharged for a long time; the data acquisition module acquisition jumps, which causes the SOC to be automatically calibrated;

　　Two conditions for SOC calibration: 1) Reach overcharge protection; 2) The average voltage reaches xxV or more. Customer battery consistency is poor, and the second condition cannot be met when overcharged. Check the remaining capacity and total capacity of the battery through the display; the current sensor is not connected correctly;