All three registers return zero even when the PV system is producing.

The PvMeter component in FEMS only exposes register values when the corresponding FEMS App (PV meter integration) is active and a physical meter is connected and communicating. Verify in the FEMS App Center that the PV meter app is installed and shows no faults. A red LED on the BMS box or an error in Online Monitoring usually points to the root cause.

The Gateway connects on port 502 but reads return exception code 02.

Exception code 02 (Illegal Data Address) means the register block is not enabled for external access. By default, the FEMS Modbus/TCP interface exposes only the _sum and ess0 component channels. Access to the PvMeter component (addresses around 11144) must be explicitly enabled in your FEMS project configuration. Contact your FEMS system integrator to confirm the correct component unlock.

Register values are off by one address compared to the Fenecon documentation.

This is a known base-address offset issue. The FEMS Modbus/TCP API requires the base address to be set to 0 in your Modbus client, not 1. If your client (or the ModbusCloud Gateway profile) defaults to 1, every register will be shifted by one. Set the base address to 0 to align with the template addresses 11144, 11174, and 11204.

Values on L2 or L3 appear stuck or always read the same as L1.

Each phase register sits at a separate address spaced 30 apart: 11144 for L1, 11174 for L2, 11204 for L3. If polling returns the same value for all three, your Modbus client may be reading three consecutive 16-bit words starting at 11144 instead of polling each address individually. Configure three separate register reads, one per address, as defined in the template.

Free Modbus template: Fenecon Dess PvMeter

The Fenecon DESS PvMeter is a per-phase PV generation measurement component within the Fenecon DESS (Distributed Energy Storage System), managed by the FEMS energy management system on OpenEMS. Over Modbus TCP, this template reads the three-phase active power registers of the PV meter: active power on L1, L2, and L3. These values let the FEMS, and your ModbusCloud portal, track live solar generation across each phase independently. Installers monitoring DESS installations use this data to detect phase imbalance, validate PV yield, and feed generation figures into multi-source energy dashboards.

Name	Address	Function	Type	Unit	Access
active_power_l1 Instantaneous AC active power on phase L1, in watts.	11144	FC03	uint16	W	R
active_power_l2 Instantaneous AC active power on phase L2, in watts.	11174	FC03	uint16	W	R
active_power_l3 Instantaneous AC active power on phase L3, in watts.	11204	FC03	uint16	W	R