14 Ways to do bms troubleshooting

Battery Management system known as the battery nanny or battery housekeeper, is an important link between the on-board power 

battery and the electric vehicle, and its main functions include: real-time monitoring of physical parameters of the battery; battery 

status estimation; on-line diagnosis and early warning; charging, discharging and pre-charging control; equalization management 

and thermal management. Battery management system (BMS) is mainly to be able to improve battery mutilation,prevent overcharging 

and over-discharging of the battery, prolong the service life of the battery, and monitor the status of the battery.

Battery management system is not only closely related to the battery, but also has various connections with the whole vehicle system, 

among all the faults, compared with other systems, the battery management system faults are relatively high, but also more difficult to

 deal with. We have summarized some common methods for dealing with battery management system failures and case studies of 

common battery management system failures for the reference of vehicle, battery and new energy management system manufacturers. 

Common Failure Case Analysis

1、System power on,but the whole system does not work

Possible reasons:Abnormal power supply, short circuit or disconnection of the wiring harness, no voltage output from DCDC

Troubleshooting:

Check whether the external power supply to the management system power supply is normal, whether it can reach the minimum operating

 voltage required by the management system to see whether the external power supply current limitation settings, resulting in insufficient 

power supply to the management system; you can adjust the external power supply, so that it meets the management system's power requirements; 

check the management system's wiring harness whether there is a short-circuit or disconnect the wiring harness is modified, so that its work is normal; 

the external power supply and wiring harness is normal. Normal, then check the management system to the entire system power supply DCDC whether 

the voltage output; if abnormal can replace the bad DCDC module 

2、BMS cannot communicate with ECU.

Possible reasons:BMU (Master Module) is not working, CAN signal line broken

Troubleshooting:

Check whether the power supply 12V/24V of BMU is normal; check whether the CAN signal transmission cable is out of pin or plugged; listen to the data

 of CAN port, whether it can receive BMS or ECU data packet. 

3、Communication between BMS and ECU is unstable.

Possible reasons:Poorly matched external CAN bus, long bus branches

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 reasons:Communication cable plug is loose, CAN wiring is not standardized, 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, whether the branch is too long; check whether the BSU address is repeated. 

5、Insulation detection alarm

Possible causes:Battery or driver leakage. The insulation module detection line is connected incorrectly.

Troubleshooting:

Use BDU display module to view the insulation detection data, check the battery bus voltage, negative bus to ground voltage is normal; use 

insulation shaking table to measure the bus and drive insulation resistance to ground.

6、The main relay does not absorb after powering on.

Possible reasons:Load detection line is not connected, pre-charging relay open circuit, pre-charge resistance open circuit.

Troubleshooting:

Use 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 pre-charging.

7、Collection module data is 0

Possible reasons:The collection module collection line is disconnected, the collection module is damaged.

Troubleshooting:

Re-plug the module wiring, measure the battery voltage in the acquisition line connector is normal, in the temperature sensor line plug to 

measure the resistance value is normal.

8. Battery current data error

Possible causes:Hall signal line plug is loose, Hall sensor is damaged, acquisition module is damaged.

Troubleshooting:

Re-plug the current Hall sensor signal line; check whether the Hall sensor power supply is normal, whether the signal output is normal;

 replace the acquisition module. 

9, Battery temperature difference is too large

Possible causes:Loose cooling fan plug, cooling fan failure.

Troubleshooting:

Re-plug the fan plug wire; supply power to the fan separately, check whether the fan is normal.

check whether the actual battery temperature is too high or too low; measure the internal resistance of the temperature probe.

10、System error after relay action

Possible causes:Relay auxiliary contact disconnection, relay contact adhesion

Troubleshooting:Re-plug the wiring harness; use a multi-meter to measure whether the auxiliary contact on and off state is correct. 

11、Can not use the charger to charge

Possible reasons:Communication between charger and BMS is not normal

Troubleshooting:Replace a charger or BMS to confirm whether it is a fault of BMS or charger; check whether the matching resistance 

of BMS charging port is normal.

12、No BMS data display on the vehicle instrument.

Possible causes:Abnormal connection of wiring harness of main control module

Troubleshooting:

Check whether the wiring harness of the main control module is well connected, whether there is normal low voltage working voltage

 in the car, and whether the module is working normally.

13、Part of the battery box test data is lost

Possible reasons:Some connectors of the whole car may have poor contact, or the BMS slave control module can't work normally.

Troubleshooting:

Check the contact condition of the connectors, or replace the BMS module. 

14、SOC abnormality

Phenomenon: SOC changes a lot during system work, or jumps repeatedly between several values; SOC has a big deviation during system 

charging and discharging; SOC keeps displaying a fixed value unchanged.