All PV registers return zero even during daylight. Why?

Registers 808 to 813 only populate when AC-coupled PV inverters are present and active in the system. Register 850 only populates when MPPT solar chargers are connected and producing. If neither device type is installed, these fields will read zero. Confirm the connected device types in the GX remote console under Device List.

The GX device is reachable but the gateway returns no response.

Modbus TCP is disabled by default on Victron GX devices. Verify it is enabled under Settings, Services, Modbus-TCP. Also confirm the gateway is polling port 502 and that no firewall rule on the local network is blocking that port between the gateway and the GX device.

I see data on some phases but not others. What is wrong?

AC-coupled PV registers are per connection point and per phase. If the PV inverter is single-phase on L1, registers for L2 and L3 (power_b, power_c, power_e, power_f) will return zero. This is normal behaviour. Only phases with active AC-coupled inverters will show non-zero values.

Function code 4 is used here but the Victron manual says FC3. Is that correct?

Yes. Victron GX devices accept both function code 3 and function code 4 for reading registers. There is no functional difference between them in the GX Modbus TCP implementation. Either code returns identical results for these system registers.

Free Modbus template: Victron Energy (pv)

The Victron Energy (pv) template reads system-level PV production data from a Victron GX device over Modbus TCP. It targets the com.victronenergy.system service at Unit ID 100, covering AC-coupled PV power on the AC output across phases L1, L2, and L3 (registers 808 to 810), AC-coupled PV power on the AC input across L1, L2, and L3 (registers 811 to 813), and total DC-coupled PV power from all connected MPPT solar chargers (register 850). Use this template to consolidate all Victron PV generation sources into a single portal view without polling individual device unit IDs.

Name	Address	Function	Type	Access
power_a AC-coupled PV power on AC output, phase L1, watts.	808	FC04	uint16	R
power_b AC-coupled PV power on AC output, phase L2, watts.	809	FC04	uint16	R
power_c AC-coupled PV power on AC output, phase L3, watts.	810	FC04	uint16	R
power_d AC-coupled PV power on AC input (grid), phase L1, watts.	811	FC04	uint16	R
power_e AC-coupled PV power on AC input (grid), phase L2, watts.	812	FC04	uint16	R
power_f AC-coupled PV power on AC input (grid), phase L3, watts.	813	FC04	uint16	R
power_g Total DC-coupled PV power from all connected MPPT solar chargers, watts.	850	FC04	uint16	R

Victron Energy (pv)

Overview

Use cases

Installation

Things to watch for

Registers (7)

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