SUN-5-12K-SG01HP3-EU-DM2 three-phase hybrid (warning codes)
Deye W31 error code
Battery communication warning: BMS data is abnormal or unstable.
Likely causes
- Loose BMS cable
- Intermittent BMS data
- Protocol mismatch
Checks to run, in order
- 1Check the BMS connection stability
- 2Check the BMS data and address
- 3Check the cable routing
Fixes
- Reseat or replace the communication cable
- Correct the protocol setting
- Restart the inverter
When to escalate
If the BMS data stays unstable, involve the distributor and the battery supplier together.
Fix it with the right tools
Check the system around the fault before replacing parts: load, battery bank, PV string and commissioning settings. If you need a second opinion, send the code and your inverter model to our team.
Before you open the inverter
- Isolate both the AC and DC sides, then confirm the display is dead before touching terminals.
- Use insulated tools and one hand where possible. DC arcs do not self-extinguish like AC.
- If you see burnt terminals, swollen cells, leaking electrolyte or a burning smell, stop and escalate instead of resetting the fault.
Questions installers ask
What does Deye W31 mean?
Battery communication warning: BMS data is abnormal or unstable.
How do I fix Deye W31?
Reseat or replace the communication cable Correct the protocol setting Restart the inverter
When should I escalate Deye W31?
If the BMS data stays unstable, involve the distributor and the battery supplier together.
Can I reset Deye W31 myself?
Only after isolating the AC and DC sides and running the checks above. If Deye W31 returns immediately, stop resetting it and escalate; a repeating fault usually points to a real circuit, battery or hardware problem.
Which models show Deye W31?
Deye W31 is documented for SUN-5-12K-SG01HP3-EU-DM2 three-phase hybrid (warning codes). Confirm the code on your own unit's display or manual before ordering parts.
More Deye error codes
- Deye F01PV input polarity is reversed at one or both DC inputs.
- Deye F02PV insulation resistance to earth is below the safety limit.
- Deye F03Ground fault detected on the PV array (GFDI).
- Deye F04GFDI ground-failure alarm: the PV array or inverter is not properly earthed.
- Deye F05Control-board EEPROM read failure.
- Deye F06Control-board EEPROM write failure.
Guidance reviewed 17 October 2026 by the Mishka Energy installer team. Error codes vary by brand, model family and firmware; confirm against the manufacturer manual.
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