Applicable Systems
BYD Battery Management System
Symptoms
The BYD BMS reports alarm BY006, indicating BMS communication interruption. The CAN bus or RS485 link between the BMS and the external controller or charger has been lost, preventing charge control and monitoring.
Possible Causes
- CAN bus cable is damaged or the connector is loose or corroded, breaking the communication link
- CAN bus termination resistor is missing or has the wrong value, causing signal reflection
- BMS CAN controller IC has failed, not transmitting or receiving CAN frames
Troubleshooting Steps
- Step 1: Check the CAN bus cable continuity and connector condition
Cable is continuous and the connector pins are clean, tight, and free of corrosion - Step 2: Verify the CAN bus termination resistors at both ends of the bus are 120 ohms
Total bus resistance is 60 ohms with two 120-ohm terminators, confirming correct termination - Step 3: Check for CAN frame activity with an oscilloscope or CAN analyzer at the BMS connector
CAN frames are present on both the transmit and receive lines with correct differential voltage levels
How to Reset
To reset: 1) Repair or replace the CAN cable and connector. 2) Install correct termination resistors. 3) Replace the BMS CAN controller if failed. 4) Restart BMS and verify communication is restored.
Source: BYD Battery Management System Manual, BYD Company Limited
Category: Battery