Applicable Systems
BYD Battery Management System
Symptoms
The BYD BMS reports alarm BY002, indicating battery pack temperature abnormality. One or more temperature sensors in the pack are reading outside the safe range, risking thermal runaway or cold-weather performance degradation.
Possible Causes
- Thermal management system has failed to cool or heat the pack, allowing temperature to drift outside the safe window
- Temperature sensor has drifted or failed, reporting a false reading that triggers the alarm
- One cell module is experiencing localized overheating due to an internal cell fault or poor inter-cell thermal contact
Troubleshooting Steps
- Step 1: Check the temperature sensor readings on the BMS interface against an infrared thermometer
Sensor readings match the infrared measurement within 2C, confirming the sensors are accurate - Step 2: Verify the thermal management system is operating, with coolant flow and heater function as required
Coolant flow is at the rated rate and the heater activates below the minimum temperature threshold - Step 3: Inspect the pack for localized hot spots using a thermal camera during charge and discharge
No localized hot spots exceeding the pack average by more than 5C are detected
How to Reset
To reset: 1) Restore thermal management system operation. 2) Replace failed temperature sensors. 3) Replace any overheating cell modules. 4) Restart BMS and verify all temperatures are within range.
Source: BYD Battery Management System Manual, BYD Company Limited
Category: Battery