The gateway connects but the power register always reads zero.

A zero reading often means the RS485 bus is wired correctly at the physical level but the slave ID does not match. Confirm the unit ID in the portal template matches the ID configured on the inverter, commonly 247. Also check that the Modbus RTU framer is selected, not RTU-over-TCP, which uses a different framing.

I keep getting CRC errors when polling the Energy Butler GEN2.

CRC errors on RS485 almost always indicate a wiring problem. Verify that only one twisted pair is used for A and B, that the GND line is connected, and that no other devices on the same bus have conflicting termination resistors. The default baud rate is 9600; mismatches between the converter and inverter settings will also cause CRC failures.

The power value has the wrong sign: import shows negative, export positive.

The GEN2 register at address 11000 is a signed int32. Some integration setups apply a scale factor of -1 to flip the sign convention. In ModbusCloud the value is presented as-is from the register; if the sign appears inverted, check whether your RS485-to-Ethernet converter is applying any transformation, and verify the sign convention in the M-TEC Modbus documentation.

After a firmware update, the gateway can no longer reach the inverter.

M-TEC changed the Modbus TCP port with firmware V27.52.4.0, moving it from port 5743 to port 502 for GEN3 devices. For GEN2 units accessed via an RS485 converter, check that the converter configuration was not reset during the update and that the baud rate and slave ID remain at their previous values.

Free Modbus template: M-TEC Energy Butler GEN2 (grid)

Name: M-TEC Energy Butler GEN2 (grid)
Brand: M-TEC
SKU: 012b1c79-7f9a-4717-9875-186cdaa7a2e1

The M-TEC Energy Butler GEN2 is a hybrid battery storage system with an integrated inverter, designed for residential and small-commercial PV installations. This template reads the grid power register at address 11000 via Modbus RTU, providing real-time measurement of power flowing to or from the public grid as reported by the built-in energy meter. Connecting the M-TEC Energy Butler GEN2 to ModbusCloud Gateway lets installers and building owners track grid exchange continuously without relying on the proprietary M-TEC portal.