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byd_bms03
Easy Fix
BYD · Electric & Hybrid Cars
Battery SOC Calibration Required
Quick Answer
Error code BYD_BMS03 on your BYD Electric & Hybrid Cars means: Battery SOC Calibration Required. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
BYD-A3BYD-DPBYD-HNBYD-SLBYD-SUBYD-SPBYD-TG
Likely Causes
  1. BMS SOC estimation model drifting from actual battery capacity after extended use
  2. Frequent partial charges without full charge cycles preventing BMS calibration updates
  3. Battery capacity reduction from aging causing a mismatch with the stored BMS capacity model
  4. Temperature-related SOC estimation error during operation in extreme climates
  5. Software update altering SOC calculation algorithm requiring re-synchronization with battery state
How to Fix It
1
Drive the vehicle until the battery reaches a low charge level of approximately 10 to 15 percent
2
Perform a full slow charge via Level 2 AC charging to 100 percent without interruption
3
Allow the vehicle to complete the full charge and rest for 30 minutes before driving
4
Check whether the SOC indicator matches expected range behavior after the calibration cycle
5
Contact BYD service if the calibration warning persists after multiple full charge cycles
Pro Tip
This is a common issue that most users can resolve without specialized tools. Try the first step before moving on to more complex solutions.
Parts You May Need
BMS firmware update if a software-related calibration fix is available
Diagnostic interface for BMS SOC model inspection
Related Error Codes
BYD_BMS01BYD_BMS02BYD_CHG01BYD_CHG02BYD_CHG03
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