All registers return zero or no data appears in the portal.

Confirm the wattsonic LAN dongle is active and reachable by pinging its IP from another device on the same network. The Modbus TCP listener runs on port 502 with unit ID 255. If the device is unreachable, check DHCP assignment or set a static IP via the inverter display menu under network settings.

Phase current values look ten times too high or too low.

The current registers at addresses 11010, 11012, and 11014 store values as uint16 in tenths of an ampere, so a raw reading of 152 represents 15.2 A. Verify that your polling client or dashboard formula applies a scale factor of 0.1 to convert raw register values to amperes.

The power register reads the wrong sign: import shows as positive when export is expected.

The wattsonic sign convention for grid power can differ by firmware version and configuration. Some community integrations apply a scale of -1 to register 11000 to match the expected sign. Check the inverter display for the current import or export direction and invert the sign in your channel configuration if needed.

Reads occasionally fail with an illegal data address error on some registers.

A known Wattsonic quirk is that some register address tables are documented with a zero-based offset, while the inverter expects a one-based address over Modbus. If a register consistently fails, try adding 1 to the address. This applies particularly when mixing register tables from different firmware documentation versions.

Free Modbus template: St-ems wattsonic (grid)

The St-ems wattsonic is a hybrid inverter platform sold under multiple brand names, including Wattsonic Gen3, and used in residential and light-commercial solar-plus-storage installations. This Modbus TCP template reads the grid connection point of the wattsonic inverter: total grid exchange power, per-phase active power across all three phases, and per-phase AC current. All values are signed, so import and export are distinguished without additional configuration. Connecting the ModbusCloud Gateway to the wattsonic over Modbus TCP gives installers live three-phase grid visibility in a single dashboard without polling the manufacturer cloud.

Name	Address	Function	Type	Unit	Access
power Total grid exchange power, signed watts; negative indicates import.	11000	FC03	int32	W	R
currents_a Grid current on phase A, in tenths of an ampere.	11010	FC03	uint16	A	R
currents_b Grid current on phase B, in tenths of an ampere.	11012	FC03	uint16	A	R
currents_c Grid current on phase C, in tenths of an ampere.	11014	FC03	uint16	A	R
powers_a Active grid power on phase A, signed watts.	10994	FC03	int32	W	R
powers_b Active grid power on phase B, signed watts.	10996	FC03	int32	W	R
powers_c Active grid power on phase C, signed watts.	10998	FC03	int32	W	R

St-ems wattsonic (grid)

Overview

Use cases

Installation

Things to watch for

Registers (7)

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