BMS Common Fault Handling Guide Battery Management System Troubleshooting Manual

BSU (Master Controller) Not Working

None

1. Abnormal 24V operating voltage — equipment power supply fault
2. CAN communication line loose, pin withdrawn, poor contact
3. Vehicle protocol box damaged — cannot transmit signal

1. Measure BSU master controller 24V operating voltage; confirm stable power supply
2. Check CAN-H and CAN-L communication lines;排查 plug looseness, pin withdrawal, and broken wire
3. If lines are normal, replace the damaged vehicle protocol box

BMS Cannot Communicate with Vehicle

BMS Communication Fault

1. CAN communication line loose, broken, or abnormal connection
2. Vehicle protocol box damaged and failed

Same as BSU not working; prioritize CAN communication line troubleshooting, then replace vehicle protocol box

Acquisition Module Communication Fault

EC-X

1. Abnormal 24V operating voltage to acquisition module
2. Acquisition module communication signal line interrupted or loose
3. Acquisition module hardware damaged

1. Measure 24V DC supply voltage; repair power supply fault
2. Inspect each acquisition signal line plug; tighten loose lines and repair withdrawn/broken pins
3. If lines and power are normal, replace the faulty acquisition module

Insulation Module Communication Fault

CRU-E

1. Abnormal 24V DC supply to insulation module — module did not start
2. Insulation module hardware damaged

1. Measure insulation module 24V supply voltage; troubleshoot power supply lines
2. If supply is normal but communication fails, directly replace the insulation module

Communication Normal but Battery Pack Indicator Light Off

None

1. CAN communication signal lines reversed (+/-)
2. CAN-H or CAN-L single signal missing

1. Verify CAN line wiring sequence; correct reversed lines
2. Measure CAN signal output port; normal voltage is approximately 2.3V DC; troubleshoot signal loss

Insulation Detection Anomaly

CRU-F

1. Battery pack relay not properly closed
2. Insulation module positive/negative detection lines reversed
3. Insulation module hardware damaged

1. Measure battery pack voltage; check if it is standard pack voltage; troubleshoot relay fault
2. Verify insulation module positive/negative detection wiring; correct errors
3. If wiring is correct, replace the insulation module; also check Hall sensor installation sequence

Current Data Displayed Inaccurately

IO-H, IC-H

1. Insulation module damaged — data acquisition failed
2. Hall signal line and ground wire reversed
3. Hall sensor hardware damaged
4. Equipment main control board damaged

1. With equipment in static state, unplug Hall line; normal reference current is ~90A; deviation indicates insulation module damage — replace
2. Check Hall line wiring method; correct reversed lines
3. If lines are normal, replace Hall sensor
4. If all above are normal, repair or replace the equipment main board

Charge/Discharge Current Polarity Displayed Opposite

None

1. Hall detection lines reversed
2. Battery positive/negative bus wiring reversed

1. Adjust Hall sensor line installation direction
2. Swap and correct battery positive and negative bus wiring

Equipment Leakage

R-E

External vehicle device leakage (inverter, generator, air pump, etc.) or battery body leakage

Sequentially disconnect high-voltage input of inverter, air pump, and other external devices to find the leakage source. If fault persists after disconnecting external devices, it is determined as battery body leakage

Battery Over-Temperature Alarm

TEMP-HX

1. Temperature sensing probe damaged or failed
2. Data acquisition module fault
3. Equipment cooling fan fault or not running — cooling failed
4. Temperature detection lines not fully inserted or poor contact

1. Verify actual battery temperature; normal temperature probe resistance is ~8kΩ at room temp; abnormal value indicates probe needs replacement
2. If probe is normal, replace the faulty acquisition module
3. Check cooling fan power supply and operating status; repair fan fault
4. Reinsert and tighten temperature detection line plugs

Excessive Battery Voltage Differential Alarm

ULH-OV

1. Actual battery cell voltage is low
2. Voltage acquisition lines loose or poor contact
3. Data acquisition module damaged
4. Equipment PCB board fuse blown

1. Measure actual cell voltage; check if battery has under-voltage
2. Comprehensively inspect voltage acquisition lines; tighten loose plugs and repair broken wires
3. If lines are normal, replace the acquisition module
4. Test PCB board fuse; replace blown fuse

Acquisition Wire Break Alarm

LBK-X

1. Battery cell voltage too low — below 200mV
2. Voltage acquisition lines broken or plug pin withdrawn/loose

1. Measure actual cell voltage; troubleshoot battery under-voltage fault
2. Inspect each acquisition circuit; repair loose, broken, or withdrawn pin issues

Equipment Cannot Charge

None

1. Communication interruption between charger and BMS system
2. Timeout between charger and BMS — unstable communication
3. Equipment leakage or severely over-discharged battery — triggers protection and cannot charge

1. Check CAN communication lines between charger and BMS; repair line faults
2. Test leakage protection and charging relay operating status; troubleshoot component faults
3. Test overall battery condition; resolve over-discharge and leakage issues before retrying charging