Why does the gateway return exception code 1 on function code 3?

Exception code 1 means the device rejected function code 3 for the requested register range. This is a known issue when polling the Solakon ONE with an incorrect unit ID or when the Modbus server has not fully started. Confirm the unit ID is set to 1 and wait up to 60 seconds after the inverter powers on before polling.

The gateway connects but all register values read as zero.

Zero readings on power and current registers are normal when the inverter is in night mode or standby with no grid interaction. Verify at a time of known grid activity. Also check that your polling start address and register count do not cross a non-contiguous register boundary, which can cause the device to return all zeros for the entire block.

Phase voltage readings seem off by a factor of 10.

The FoxESS and Solakon Modbus register map stores voltages as int16 with a scaling factor of 0.1 applied in the protocol layer. If your client reads raw counts without applying a 0.1 multiplier, values will appear ten times too high. Apply the correct scaling in your ModbusCloud template or data processing step.

The inverter IP address keeps changing and polling drops out.

The Solakon ONE acquires its IP via DHCP and there is no documented way to set a static IP from the device interface. To prevent dropouts, assign a DHCP reservation for the inverter's MAC address in your router. This pins the IP without requiring changes on the inverter itself.

Free Modbus template: Solakon ONE (grid)

The Solakon ONE is a compact hybrid inverter and battery storage unit designed for residential and small-commercial solar installations, including balcony power station setups. Sold under the Solakon ONE, Avocado, Avocado Pro, and MQ2200 names, it communicates over Modbus TCP on port 502. This grid-side template reads total grid active power (import and export), cumulative energy, and per-phase voltages and currents for all three phases. With these registers in your ModbusCloud portal, you can track grid interaction in real time, detect phase imbalances, and maintain an auditable energy record.

Name	Address	Function	Type	Unit	Access
power Total grid active power, signed; positive is export, negative is import.	39168	FC03	int32	W	R
energy Cumulative grid energy counter, monotonically increasing.	39625	FC03	uint32	Wh	R
voltages_a Phase A AC voltage at the grid connection point.	39123	FC03	int16	V	R
voltages_b Phase B AC voltage at the grid connection point.	39124	FC03	int16	V	R
voltages_c Phase C AC voltage at the grid connection point.	39125	FC03	int16	V	R
currents_a Phase A AC current flowing to or from the grid.	39126	FC03	int32	A	R
currents_b Phase B AC current flowing to or from the grid.	39128	FC03	int32	A	R
currents_c Phase C AC current flowing to or from the grid.	39130	FC03	int32	A	R

Solakon ONE (grid)

Overview

Use cases

Installation

Things to watch for

Registers (8)

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