No values appear after import, though the gateway connects.

Confirm the Modbus framer is set to RTU, not plain TCP socket mode. The M-Tec MTec uses RTU framing over TCP via the espressif server. Also verify the slave ID is 252 and the port matches your firmware version: 5743 for firmware before V27.52.4.0, or 502 for that version and newer.

Power and energy registers return zero or implausible values.

Registers 706 and 707 are signed 16-bit integers. If your polling tool or gateway interprets them as unsigned, large negative values will appear as very high positive numbers. Ensure the data type is configured as int16. Also check that the inverter is actively running, as some devices report zero when idle.

Temperature register 401 reads a value that seems too high or too low.

Confirm whether a scaling factor applies. M-TEC Modbus documentation for similar devices sometimes encodes temperature as tenths of a degree Celsius (value divided by 10). Cross-check the raw register value against the inverter's local display or portal to determine the correct scaling for your firmware version.

Is it safe to write to the setmaxpower register at address 1000?

Use the setmaxpower write register with care. Setting a value below the inverter's configured minimum or above its rated capacity can trigger protection responses or affect warranty conditions. Always test with conservative values, confirm the inverter accepts the setpoint via the power register, and coordinate with the M-TEC installer before enabling automated writes.

Free Modbus template: M-Tec MTec

The M-Tec MTec is a hybrid battery storage inverter from Austrian manufacturer M-TEC, part of the Energy Butler product family. It combines a PV inverter with integrated battery management and communicates over Modbus RTU. This template reads instantaneous AC output power (register 706), accumulated energy (register 707), and internal temperature (register 401). A write register at address 1000 lets your control system cap the inverter's maximum output power. Connecting this template in ModbusCloud gives installers and asset managers live visibility and setpoint control across one or more M-Tec sites.

Name	Address	Function	Type	Unit	Access
setmaxpower Maximum power setpoint written to the inverter, in watts.	1000	FC16	int16	W	W
power Instantaneous AC output power of the inverter.	707	FC03	int16	W	R
energy Accumulated energy value reported by the inverter.	706	FC03	int16	Wh	R
temp Internal temperature reading of the inverter or battery unit.	401	FC03	int16	°C	R