All registers return zero or no data after connecting. Why?

The FEMS Modbus/TCP read app must be active on the Fenecon system. Open the FEMS portal, navigate to Settings, System Profile, and confirm ctrlApiModbusTcp is installed and running. Without this app enabled, the TCP port does not serve register data.

Register addresses are off by one compared to the FEMS export. What is wrong?

Some Modbus clients default their base address to 1 instead of 0. The FEMS Modbus table uses base address 0. Set your client's base address offset to 0; otherwise every address from the system profile will appear shifted by one register.

The gateway connects but soc and energy registers read unexpected values. Any known quirks?

The 32-bit energy registers (original_active_charge_energy at 10151 and original_active_discharge_energy at 10153) each span two consecutive 16-bit holding registers. Confirm your client reads them as uint32 across both registers in big-endian order, which is standard for FEMS.

The system_state or bsmu_work_state values do not change. Is the device stuck?

These state registers reflect internal BSMU and inverter state machines. A constant value is normal during steady charge or discharge. Cross-check against the live FEMS monitoring dashboard: if the portal shows state changes but the Modbus value is frozen, check for network packet loss between the Gateway and the FEMS controller.

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Brand: Fenecon
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Registers (12)

12 read / 0 write

Name	Address	Function	Type	Unit	Access
system_state Overall ESS operating state enumeration.	10000	FC03	uint16		R
bsmu_work_state Battery stack management unit current work state.	10001	FC03	uint16		R
stack_charge_state Battery stack charge/discharge state enumeration.	10002	FC03	uint16		R
soc Battery state of charge, 0 to 100 percent.	10143	FC03	uint16	%	R
original_active_charge_energy Cumulative active energy charged into the battery, watt-hours.	10151	FC03	uint32	Wh	R
original_active_discharge_energy Cumulative active energy discharged from the battery, watt-hours.	10153	FC03	uint32	Wh	R
active_power_l1 AC active power on phase L1, watts.	11133	FC03	uint16	W	R
reactive_power_l1 AC reactive power on phase L1, volt-amperes reactive.	11134	FC03	uint16	W	R
active_power_l2 AC active power on phase L2, watts.	11163	FC03	uint16	W	R
reactive_power_l2 AC reactive power on phase L2, volt-amperes reactive.	11164	FC03	uint16	W	R
active_power_l3 AC active power on phase L3, watts.	11193	FC03	uint16	W	R
reactive_power_l3 AC reactive power on phase L3, volt-amperes reactive.	11194	FC03	uint16	W	R