FENECON Modbus-API (battery)
The FENECON Modbus-API is the built-in Modbus TCP interface of FENECON energy storage systems, powered by the FEMS energy management software. It exposes aggregated system channels over a local Ethernet connection, making battery data available to external controllers, building management systems, and monitoring platforms without additional hardware. This template reads the two core battery registers: discharge power at address 415 and state of charge at address 302. Connecting the ModbusCloud Gateway to the same LAN as the FEMS gives you continuous visibility into battery behaviour across one or more FENECON installations.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 2, read only
- Brand
- FENECON
- Compatible models
- Modbus-API
- Last updated
Registers (2)
2 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| power | W | Read | |||
| soc | % | Read |
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Use cases
- Monitor battery state of charge continuously to detect prolonged low-SoC conditions indicating degradation.
- Track discharge power over time to verify the battery is delivering expected output during peak demand hours.
- Alert on state of charge dropping below a defined threshold to prevent deep discharge events.
- Compare discharge power readings against consumption data to validate self-consumption optimisation performance.
- Report daily charge and discharge cycles across multiple FENECON sites from a single ModbusCloud portal view.
Installation
Verify that the FEMS Modbus TCP read-access app is active on your FENECON system: log in to FEMS Online Monitoring, open Settings, open the system profile, and confirm ctrlApiModbusTcp is present and enabled.
Connect the ModbusCloud Gateway to the same LAN as the FEMS unit so it can reach the FEMS IP address directly; note the FEMS IP address and confirm TCP port 502 is reachable from the Gateway.
In the ModbusCloud portal, add the Gateway, import the FENECON Modbus-API (battery) template, and set the unit ID to 1 (the default for FEMS Modbus TCP read access).
Spot-check register 302 in the portal live view and compare the returned state-of-charge value against the FEMS Online Monitoring dashboard to confirm the connection is reading correctly.
Things to watch for
Register 302 returns a value that is off by one address. Why?
FEMS Modbus tools default to a base address of 1, which shifts all register addresses by one position. Ensure your Modbus client and the ModbusCloud Gateway use a base address of 0. With base address 0, register 302 correctly returns the battery state of charge.
The Gateway connects but register 415 always reads zero or stale data.
Register 415 reports discharge power and returns zero when the battery is idle or actively charging. Negative float32 values indicate charging. Confirm the battery is in an active charge or discharge cycle before concluding there is a communication problem.
No values appear at all after importing the template. What should I check?
The ModbusCloud Gateway must be on the same physical network as the FEMS unit and able to reach its IP address directly. Firewalls or VLANs that block TCP port 502 will prevent all register reads. Verify network routing and confirm no firewall rule is blocking Modbus traffic on that port.
The power register uses float32. What does that mean for reading two registers?
A float32 value spans two consecutive 16-bit Modbus registers. Function code 4 must request two registers starting at address 415. If your client requests only one register, the returned value will be incomplete and appear as garbage. Ensure the data type is set to float32 in your Modbus client configuration.
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