CauseShort circuit happen at PV port.
Recommended fixCheck if wiring is connect well.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
Felicity Apollo-5KLP1G01-MX Error Codes: Causes & Fixes (49 codes)
This is the complete fault table for the Felicity Apollo-5KLP1G01-MX Energy storage system family — 49 codes shared by 6 model numbers, transcribed from the official manual. On this Felicity 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 coversApollo-5KLP1G01-M1Apollo-5KLP1G01-M2Apollo-4K6LP1G01-MXApollo-4K6LP1G01-M1Apollo-4K6LP1G01-M2
Last checked against the official manuals on July 10, 2026.
How to read the severity labels
- Critical(27)— unit trips offline — do not restart before checking
- Fault(16)— operation stops until cleared
- Warning(6)— unit keeps running · needs attention
Critical codes (27)unit trips offline — do not restart before checking
CausePV current sensor failed.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
Abnormal LLC converter operation.
CauseThe internal LLC DC-DC converter stage is operating abnormally. This is an internal power-conversion fault, not something caused by wiring or settings.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
Over current detected at the Buckboost stage.
CauseOver current at Buckboost.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
BuckBoost converter is out of balance.
CauseBuckBoost is out of balance.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
CauseBuckboost current sensor failed.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Number 2 Buckboost current sensor failed.
CauseNO.2 Buckboost current sensor failed.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Output short circuit detected.
CauseOutput short circuited.
Recommended fixCheck if wiring is connected well and remove abnormal load.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Output current sensor failed.
CauseOutput current sensor failed.
Recommended fixOutput current sensor failed.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
CauseOutput voltage is too high.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Over current or surge detected by software protection.
CauseOver current or surge detected by software.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Hardware detected over current at inverter port.
CauseHardware detect over current at inverter port.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Invert soft start failed; internal components failed.
CauseInternal components failed.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
CauseThe DC component of the inverter current is abnormal.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
CauseInverter current sensor failed.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
CauseBus voltage is too low.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Bus voltage is too high; AC surge or internal components failed.
CauseAC Surge or internal components failed.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Bus soft start failed; internal components failed.
CauseInternal components failed.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Leakage current fault detected.
CauseLeakage current fault.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
CauseLeakage current sensor failed.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
CauseIsolation resistance to ground of the PV string is too low.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
Relay self-check failure.
CauseRelay check failure.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
CauseThe EEPROM that stores the inverter's settings and calibration data failed a read/write check. This is an internal memory component fault.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
CauseDSP1 communication failure.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
CauseDSP2 communication failure.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
CauseTemperature sensor disconnected.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
CauseBattery input circuit failure.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
Fault codes (16)operation stops until cleared
PV input voltage exceeds the allowed maximum.
CausePV voltage is too high.
Recommended fixReduce the number of PV modules in series.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
Over current detected at PV port.
CauseOver current happen at PV port.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
Battery voltage exceeds the maximum allowed value.
CauseBattery voltage is too high.
Recommended fixCheck if spec and quantity of batteries are meet requirements.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
Overload condition timed out.
CauseThe connected load exceeded the inverter's overload capacity for longer than the allowed time, so the overload timer expired and the unit shut the output down.
Recommended fixReduce the connected load by switching off some equipment.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Input and output wiring reversed.
CauseInput output reverse.
Recommended fixConfirm that the input and output wiring is correct.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
CauseOutput voltage is too low.
Recommended fixReduce the connected load.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Over temperature condition at the heat sink.
CauseOver temperature happen at heat sink.
Recommended fixCheck whether the ambient temperature is too high.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Inner temperature exceeds the allowed limit.
CauseThe inner temperature over.
Recommended fixCheck whether the ambient temperature is too high.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 43
Parallel CAN communication abnormality.
CauseParallel CAN COMM abnormality.
Recommended fixTest the parallel communication line, restart still have problems please contact the after-sales service.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
Loss of parallel hosts in parallel system.
CauseLoss of parallel hosts.
Recommended fixTest the parallel communication line, restart still have problems please contact the after-sales service.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
Parallel synchronisation signal abnormal.
CauseParallel Synchronisation Signal Abnormal.
Recommended fixTest the parallel communication line, restart still have problems please contact the after-sales service.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
Inconsistency in firmware versions across paralleled inverters.
CauseInconsistency in parallel versions.
Recommended fix1. Update all inverter firmware to the same version. 2. Check the version of each inverter via the LCD settings to ensure that the CPU versions are the same. if it is not the same, please contact after-sales personnel to update the firmware. 3. After updating, if the problem still exists, please contact after-sales.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
Inconsistent parallel settings; single-phase parallel system and group three-phase system setup error.
CauseSingle-phase parallel system and group three-phase system setup error.
Recommended fixSingle-phase parallel system and group three-phase system setup error.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
Failure of the parallel system as a whole; specific faults in other machines in the parallel system.
CauseSpecific faults in other machines in the parallel system.
Recommended fixSpecific faults in other machines in the parallel system.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
Parallel negative power protection triggered.
CauseParallel negative power protection.
Recommended fixRestart the unit, if the error persists, contact the repair center.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
PV parallel failure; PV1 and PV2 paralleling configuration mismatch.
CausePV1 and PV2 paralleling configuration mismatch.
Recommended fixPlease confirm whether PV1 and PV2 need to be set to parallel mode. if not, please turn off this function in APP. if necessary, please confirm whether the wiring of PV1 and PV2 is connected to parallel mode.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 44
Warning codes (6)unit keeps running · needs attention
Low battery warning shown on LCD with flashing error icon.
CauseThe battery voltage is too low.
Recommended fixIt should be charging.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
Overload warning. Audible alarm: beep twice every second.
CauseThe connected load is drawing more power than the inverter's rated output capacity; the unit is warning before overload protection cuts the output.
Recommended fixPower down the inverter, wait 5 minutes for capacitors to discharge, then restart. If the fault recurs immediately or repeatedly, record the exact code and contact your installer or the manufacturer's service line.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
Phase sequence error warning between input and output AC power lines.
CauseThe AC input and output power lines are connected in the wrong phase order, so the phase sequence between the input and output sides does not correspond.
Recommended fixCheck that the input and output power lines correspond.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
BMS does not allow the inverter to discharge battery; inverter will stop discharging battery automatically.
CauseBMS doesn't allow inverter to discharge battery.
Recommended fixInverter will stop discharging battery automatically.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
BMS requires inverter to charge battery; inverter will charge battery automatically.
CauseBMS require inverter to charge battery.
Recommended fixInverter will charge battery automatically.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
BMS firmware version is not matched with the inverter.
CauseBMS firmware version is not matched.
Recommended fixUpgrade the firmware of BMS.
Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf· page 42
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Common questions about Apollo-5KLP1G01-MX error codes
- What is the difference between a fault and a warning on the Apollo-5KLP1G01-MX?
- A fault puts the unit into protection and stops normal operation — this page lists 43 of them for the Apollo-5KLP1G01-MX. A warning leaves the unit running; there are 6 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 Apollo-5KLP1G01-MX shares its firmware and fault table with 5 other model numbers: Apollo-5KLP1G01-M1, Apollo-5KLP1G01-M2, Apollo-4K6LP1G01-MX, Apollo-4K6LP1G01-M1, Apollo-4K6LP1G01-M2. 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 Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf — Felicity'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 Felicity user manuals. Always consult your device manual and a qualified technician before performing repairs.