CauseThe PV (DC) input is connected with reversed polarity.
Recommended fixCheck the PV input polarity and correct the wiring. Seek help from Deye if the system cannot go back to the normal state.
Source:002_Download_4e90fe7a.pdf· page 46
DEYE AI-W5.1 ESS Error Codes: Causes & Fixes (25 codes)
This is the complete fault table for the DEYE AI-W5.1 ESS Energy storage system family — 25 codes shared by 5 model numbers, transcribed from the official manual. On this DEYE device, a fault code means the unit has entered protection and stopped normal operation; a warning leaves it running. The exact indication (LED pattern or display code) is listed per code below.
Also coversAI-W5.1-5P3-EU-B-ESSAI-W5.1-6P3-EU-B-ESSAI-W5.1-8P3-EU-B-ESSAI-W5.1-10P3-EU-B-ESSAI-W5.1-12P3-EU-B-ESS
Last checked against the official manuals on July 11, 2026.
How to read the severity labels
- Fault(23)— operation stops until cleared
- Warning(1)— unit keeps running · needs attention
- Info(1)— status message · no action forced
Fault codes (23)operation stops until cleared
DC start failure - the internal BUS voltage cannot be built up.
CauseNeither PV nor battery could establish the internal BUS voltage at start-up - insufficient input voltage or a start-up circuit fault.
Recommended fixRestart the inverter. if the fault still exists, contact Deye for help.
Source:002_Download_4e90fe7a.pdf· page 46
AC side over-current fault (software detection).
CauseThe combined backup-load and common-load power exceeded the inverter's AC output range.
Recommended fixCheck that the backup load power and common load power are within range, restart, and check whether operation is normal. Seek help from Deye if it does not recover.
Source:002_Download_4e90fe7a.pdf· page 46
Leakage current fault (GFCI).
CauseGround-leakage current exceeded the limit - typically a PV-side cable ground/insulation problem.
Recommended fixCheck the PV-side cable ground connection and restart the system 2-3 times. if the fault still exists, contact Deye for help.
Source:002_Download_4e90fe7a.pdf· page 46
AC side over-current fault (hardware detection).
CauseThe combined backup-load and common-load power exceeded the inverter's AC output range, tripping the hardware over-current protection.
Recommended fixCheck that the backup load power and common load power are within range, restart, and check whether operation is normal. Seek help from Deye if it does not recover.
Source:002_Download_4e90fe7a.pdf· page 46
DC side over-current fault (hardware detection).
CauseDC-side current exceeded the hardware limit - a PV module or battery connection problem, or an off-grid start-up with a large load.
Recommended fixCheck the PV module and battery connections; in off-grid mode reduce the connected load. Turn off the DC and AC switches, wait one minute, then turn them back on; seek help from Deye if it does not recover.
Source:002_Download_4e90fe7a.pdf· page 46
BUS over-current.
CauseCurrent on the internal high-voltage BUS exceeded the limit - PV input current or battery current settings too high.
Recommended fixCheck the PV input current and battery current settings, and restart the system 2-3 times. if the fault still exists, contact Deye for help.
Source:002_Download_4e90fe7a.pdf· page 47
Leakage current fault (transient GFCI over-current).
CauseA transient ground-leakage over-current was detected - typically a PV-side cable ground/insulation problem.
Recommended fixCheck the PV-side cable ground connection and restart the system 2-3 times. if the fault still exists, contact Deye for help.
Source:002_Download_4e90fe7a.pdf· page 47
PV isolation resistance is too low.
CauseThe PV array's insulation resistance to ground is below the limit - damp or damaged PV wiring, or the inverter PE cable is not properly grounded.
Recommended fixCheck that the PV panel connections to the inverter are firm and correct and that the inverter's PE cable is connected to ground. Seek help from Deye if it does not recover.
Source:002_Download_4e90fe7a.pdf· page 47
CauseLarge load-power differences between the three phases, or DC leakage current, unbalanced the internal DC bus.
Recommended fixWait a while and check whether it returns to normal; balance the loads across phases and restart the system 2-3 times. Seek help from Deye if it persists.
Source:002_Download_4e90fe7a.pdf· page 47
Parallel CAN communication fault.
CauseIn parallel mode, the parallel communication cable connection or inverter communication-address setting is wrong; inverters also report F29 transiently during parallel-system start-up.
Recommended fixCheck the parallel communication cable connections and the communication address setting of each inverter. During start-up it disappears automatically once all inverters are ON; if it still exists, contact Deye for help.
Source:002_Download_4e90fe7a.pdf· page 47
AC overload fault on the backup output.
CauseThe backup load power exceeded the allowed output power range.
Recommended fixCheck the connected backup load and make sure it is within the allowed power range. if the fault still exists, contact Deye for help.
Source:002_Download_4e90fe7a.pdf· page 47
CauseOne inverter in the parallel system shut down, so all paralleled hybrid inverters report F41.
Recommended fixCheck the work status of every hybrid inverter in the parallel system and restore the one that shut down. if the fault still exists, contact Deye for help.
Source:002_Download_4e90fe7a.pdf· page 47
Grid voltage fault - AC line voltage out of range (low).
CauseThe grid AC voltage is outside (below) the standard voltage range in the specification, or the grid AC cables are loose or incorrectly connected.
Recommended fixCheck that the AC voltage is within the standard range and that the grid AC cables are firmly and correctly connected. Seek help from Deye if it does not recover.
Source:002_Download_4e90fe7a.pdf· page 47
Backup battery fault - paralleled batteries are inconsistent.
CauseOne of the connected batteries has voltage, SOC, or parameter settings that do not match the others.
Recommended fixCheck each battery's status (voltage, SOC, and parameters) and make sure all parameters are the same. if the fault still exists, contact Deye for help.
Source:002_Download_4e90fe7a.pdf· page 48
Grid frequency out of range (too high).
CauseThe grid frequency is above the range configured in the specification, or the AC cables are loose/incorrectly connected.
Recommended fixCheck that the grid frequency is within the specified range and that the AC cables are firmly and correctly connected. Seek help from Deye if it does not recover.
Source:002_Download_4e90fe7a.pdf· page 48
Grid frequency out of range (too low).
CauseThe grid frequency is below the range configured in the specification, or the AC cables are loose/incorrectly connected.
Recommended fixCheck that the grid frequency is within the specified range and that the AC cables are firmly and correctly connected. Seek help from Deye if it does not recover.
Source:002_Download_4e90fe7a.pdf· page 48
BUS voltage is too high.
CauseThe internal BUS voltage exceeded its limit - battery voltage too high or PV input voltage above the allowed range.
Recommended fixCheck whether the battery voltage is too high and that the PV input voltage is within the allowed range. Seek help from Deye if it does not recover.
Source:002_Download_4e90fe7a.pdf· page 48
BUS voltage is too low (battery voltage low).
CauseThe internal BUS voltage is below its limit - typically the battery voltage is too low.
Recommended fixCheck whether the battery voltage is too low; if so, use PV or grid to charge the battery. Seek help from Deye if it does not recover.
Source:002_Download_4e90fe7a.pdf· page 48
Battery BMS communication lost.
CauseCommunication between the hybrid inverter and the battery BMS disconnected while 'BMS_Err-Stop' is active.
Recommended fixRestore the BMS communication link (cable, pinout, protocol). if you do not want the inverter to stop on BMS loss, disable the 'BMS_Err-Stop' item on the LCD. if the fault still exists, contact Deye for help.
Source:002_Download_4e90fe7a.pdf· page 48
DRM0 stop (demand response, Australia).
CauseThe DRM0 demand-response signal commanded the inverter to stop, or the DRM function is enabled where it is not in use (the DRM function is for the Australia market only).
Recommended fixCheck whether the DRM function is active and disable it if unused. Seek help from Deye if the inverter does not return to normal after a system restart.
Source:002_Download_4e90fe7a.pdf· page 48
DC arc fault detected (US market only).
CauseA DC arc was detected in the PV wiring - typically a loose, damaged, or corroded PV module cable connection (ARC detection is for the US market only).
Recommended fixCheck the PV module cable connections, repair the arcing point, and clear the fault. Seek help from Deye if it does not return to normal.
Source:002_Download_4e90fe7a.pdf· page 48
Heat sink temperature is too high.
CauseThe inverter heat-sink temperature exceeded its limit - working environment temperature too high or insufficient cooling.
Recommended fixCheck whether the work environment temperature is too high; turn the inverter off for 10 minutes and restart. Seek help from Deye if it does not recover.
Source:002_Download_4e90fe7a.pdf· page 48
Warning codes (1)unit keeps running · needs attention
Working mode change notice.
CauseReported when the grid type/frequency setting changes, when the battery mode is set to 'No battery', or (on older firmware) when the system work mode changes.
Recommended fixIt generally disappears automatically. if it stays, turn off the DC and AC switches, wait one minute, and turn them back on; seek help from Deye if it will not clear.
Source:002_Download_4e90fe7a.pdf· page 46
Info codes (1)status message · no action forced
Remote shutdown - the inverter is being remotely controlled.
CauseA remote shutdown command is active; the inverter has been stopped by remote control.
Recommended fixClear or release the remote shutdown command from the remote-control source to resume operation.
Source:002_Download_4e90fe7a.pdf· page 47
Still seeing a code on your AI-W5.1 ESS?
Send us the code on your screen and a DEYE technician will reply with the exact steps for your unit. Support is free for life — a first diagnosis never needs a callout.
Keep troubleshooting
- All DEYE error codesSearch every device and code in the database
- Deye Inverter Error Codes List — Every Fault Code Meaning + Fix (F13, F18, F35…)The step-by-step troubleshooting guide
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Common questions about AI-W5.1 ESS error codes
- What is the difference between a fault and a warning on the AI-W5.1 ESS?
- A fault puts the unit into protection and stops normal operation — this page lists 23 of them for the AI-W5.1 ESS. A warning leaves the unit running; there are 1 warning codes here. Resolve the cause of a fault before restarting; warnings can usually be cleared while the unit runs.
- Which model numbers does this page cover?
- The AI-W5.1 ESS shares its firmware and fault table with 4 other model numbers: AI-W5.1-5P3-EU-B-ESS, AI-W5.1-6P3-EU-B-ESS, AI-W5.1-8P3-EU-B-ESS, AI-W5.1-10P3-EU-B-ESS, AI-W5.1-12P3-EU-B-ESS. If your unit is any of these, every code on this page applies to it.
- Where do these codes come from?
- Every entry was transcribed from 002_Download_4e90fe7a.pdf — DEYE's official documentation. Each row cites its source manual (and page where printed), so you can verify the wording before acting on it.
Compiled from official DEYE user manuals. Always consult your device manual and a qualified technician before performing repairs.