Why do power_a and power_b return obviously wrong or huge values?

The Solarlog uses a mixed byte order for 32-bit values: bytes within each 16-bit word are Big-Endian, but the two words of a 32-bit value are stored Little-Endian (low word first, high word second). If your client reads them as standard Big-Endian uint32, the result will be wrong. Ensure the ModbusCloud template applies the correct word-swap interpretation for both registers.

The gateway connects but both registers return zero constantly.

The Modbus TCP free interface on the Solarlog only reports non-zero values when at least one inverter is communicating with the logger. Verify that the Solarlog web interface shows live inverter data. Also confirm that the free Modbus TCP interface is enabled and not the licensed PM interface, which uses a different register map.

Readings update very slowly or appear frozen in the portal.

The Solarlog refreshes its internal data every 15 to 60 seconds depending on configuration. Modbus reads between refresh cycles return the last cached value, not a real-time sample. This is normal device behaviour. Adjust your polling interval in ModbusCloud to 60 seconds to stay in sync with the Solarlog update cycle.

Connection is refused on port 502. What should I check?

The Solarlog free Modbus TCP interface listens on port 502 only when explicitly enabled in the device configuration under Digital Interfaces. Verify the feature is active in the Solarlog web UI. Also check that no firewall on the local network blocks port 502 between the ModbusCloud Gateway and the Solarlog IP address.

Free Modbus template: Solarlog Solarlog (grid)

The Solarlog is a PV system monitoring gateway that aggregates data from all connected inverters and meters into a single Modbus TCP interface. This template reads two key grid-side registers from the Solarlog (grid) profile: power_a, the total active generation power, and power_b, the total site consumption power. Both are read via function code 4 from the Solarlog free Modbus TCP interface, requiring no license. Connecting the ModbusCloud Gateway to the Solarlog gives installers and asset managers a live view of generation versus consumption in one dashboard.

Name	Address	Function	Type	Unit	Access
power_a Total AC power currently generated by all connected PV inverters, in watts.	3502	FC04	uint32	W	R
power_b Total AC power currently consumed by the site loads, in watts.	3518	FC04	uint32	W	R