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Analysis by Marcus & Team

EG4 18KPV Fault Code F89: Auxiliary Power Supply Failure

Troubleshoot EG4 18KPV F89 error: Auxiliary power supply fault. Diagnose power issues in residential solar hybrid inverters. Resolve F89 errors safely.

Frequently Asked Questions

•What are the typical input voltage ranges for the EG4 18KPV auxiliary power supply?

The auxiliary power supply typically accepts a DC input voltage range of 20-60V from the battery or DC bus, and an AC input voltage of 90-260V.

•How do I safely discharge the capacitors in the EG4 18KPV inverter before working on the auxiliary power supply?

After disconnecting AC and DC power, wait at least 5 minutes for the capacitors to discharge naturally. Verify with a calibrated multimeter that the DC bus voltage is below 50V before proceeding.

•Where can I find the specifications and replacement parts for the EG4 18KPV auxiliary power supply?

Refer to the EG4 18KPV service manual or contact EG4 technical support for specifications. Replacement parts can be obtained from EG4 or authorized distributors.

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Marcus leads the technical research department at Storage Faults. Together with a team of systems analysts, he specializes in translating complex solar storage error codes into actionable diagnostic steps for the US market.

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How It Works:

The EG4 18KPV is a hybrid inverter which integrates solar PV input, battery storage, and grid interconnection. The auxiliary power supply (APS) provides DC power to the inverter's control circuits (microcontroller, gate drivers, sensors, display). Failure of the APS prevents proper inverter startup, MPPT operation, battery charging, grid synchronization, and protection functions. The APS typically operates from the DC bus or the AC grid, and generates multiple low-voltage DC rails (e.g., 5V, 12V) required for digital and analog circuits. The control board relies on the APS.

Possible Causes:

Failure of the APS internal components (capacitors, MOSFETs, ICs) due to aging or thermal stress.
Overload on the APS output, caused by a short circuit in one of the powered control circuits.
Input voltage problem to the APS (DC bus undervoltage, AC grid voltage sag or surge).
Firmware glitch causing incorrect APS operation or false fault detection.
Loose wiring connections to the APS, resulting in voltage drops or intermittent power supply.
Damage to the APS due to a surge event on the AC or DC side.

Safety Warning:

Working with electrical equipment is inherently dangerous. The EG4 18KPV inverter operates at high voltages (DC up to 600V+), which can cause serious injury or death. Arc flash hazards exist. Always disconnect all power sources before performing any maintenance or repairs. A qualified electrician is required for all repairs. Follow all applicable NEC codes and manufacturer's safety guidelines. Verify rapid shutdown system is engaged and functioning prior to service.

Step-by-Step Fix:

1

*Safety First**: Disconnect both AC and DC power to the EG4 18KPV inverter following NEC 690.15 requirements. Verify complete power shutdown with a calibrated multimeter. Engage rapid shutdown system if applicable, following NEC 2017/2020 guidelines. Wait 5 minutes for capacitor discharge.
2

*Visual inspection**: Carefully inspect the APS module (if accessible) for any signs of physical damage, such as bulging capacitors, burnt components, or loose wires. Note any unusual odors.
3

*Voltage Checks**: With the inverter disconnected from AC and DC power, use a multimeter to check the input and output voltages of the APS module (if accessible). Compare the readings to the APS module specifications on the label. Resistance check of APS output to ground for shorts.
4

*Wiring inspection**: Inspect all wiring connections to the APS module for looseness, corrosion, or damage. Re-torque connections to the manufacturer's specified torque rating using a calibrated torque wrench.
5

*Component Testing**: If accessible and qualified, use a multimeter to test the individual components within the APS module (e.g., capacitors, diodes, MOSFETs) for proper function. Desolder components if necessary for accurate testing.
6

*Firmware Update/Reset**: If the APS module is controlled by firmware, attempt to update or reset the firmware to the latest version. Refer to the EG4 documentation for the correct procedure. Contact EG4 support for firmware files.
7

*APS Replacement**: If the APS module is determined to be faulty, replace it with a new, identical module from EG4 or an authorized distributor. Ensure proper grounding and heat sinking.

Observed Symptoms:

Inverter displays fault code F89, accompanied by a potential loss of AC output, failure to charge batteries from either solar or grid, and unresponsive LCD screen or monitoring app.

Prevention:

Periodically inspect the inverter for proper cooling and ventilation to prevent overheating of the APS
Check for loose wiring connections and re-torque as needed
Keep the inverter firmware up to date
Log temperature trends via monitoring if possible, and check for abnormal behavior