The gateway connects but all register values show NaN. Why?

SMA devices return NaN for registers whose data originates from the power-electronics CPU when that CPU is inactive. For the Sunny Island this can occur during standby. Confirm the inverter is in an active operating state by checking the system_state register (30201) first, then retry reads.

I receive Modbus error code 11 on every request. What is wrong?

Error code 11 means the unit ID in your request does not match the unit ID configured on the inverter. The SMA default unit ID is 3. Open the inverter's communication settings, read the configured unit ID, and update the corresponding field in your ModbusCloud portal gateway configuration to match exactly.

Write registers for active power and control mode have no effect. Why?

Power setpoint control via the Sunny Island Modbus interface is only possible during parallel grid operation, not in stand-alone or island mode. Confirm the system_state register shows grid-parallel operation. Also note that some grid-management parameters require prior Grid Guard authentication via register 43090 before writes are accepted.

Is it safe to write setpoints to set_active_power or min_soc registers frequently?

Use caution with write registers. The set_active_power and set_reactive_power setpoints may be written cyclically, but parameters such as min_soc_power_on and min_soc_power_off are stored in flash memory. Writing these too frequently risks flash wear and may affect battery protection thresholds. Grid Guard-protected registers also require re-authentication after every inverter restart.

Free Modbus template: SMA SunnyIsland

The SMA Sunny Island is a battery inverter designed for off-grid and grid-backup applications, used in residential, commercial, and agricultural energy storage installations. This Modbus TCP template reads device identity registers, system state, fault codes, and per-phase AC measurements including active power, reactive power, and grid voltage across all three phases. Battery monitoring covers state of charge, current, voltage, temperature extremes, and both cumulative charge and discharge energy. Write registers expose active power, reactive power, and control mode setpoints, plus SoC-based shutdown thresholds. Use this template to monitor and remotely control your SMA Sunny Island from the ModbusCloud portal.

Registers (41)

35 read / 6 write

Name	Address	Function	Type	Unit	Access
device_class Numeric code identifying the SMA device class category.	30051	FC03	uint32		R
device_type Numeric code identifying the specific SMA device type.	30053	FC03	uint32		R
serial_number Factory serial number of the Sunny Island unit.	30057	FC03	uint32		R
software_package Installed firmware version, BCD-encoded in four bytes.	30059	FC03	uint32		R
waiting_time_until_feed_in Remaining countdown before the inverter resumes grid feed-in.	30199	FC03	uint32	s	R
system_state Current operating state code of the Sunny Island system.	30201	FC03	uint32		R
recommended_action Encoded code for the action recommended by the device.	30211	FC03	uint32		R
message Active event or status message code from the device.	30213	FC03	uint32		R
fault_correction_measure Encoded code indicating the suggested fault-correction step.	30215	FC03	uint32		R
max_apparent_power Rated maximum apparent power output of the inverter, watts.	30231	FC03	uint32	W	R
active_charge_energy Cumulative AC energy delivered to charge the battery, watt-hours.	30595	FC03	uint32	Wh	R
active_discharge_energy Cumulative AC energy drawn from the battery during discharge, watt-hours.	30597	FC03	uint32	Wh	R
active_power Total three-phase AC active power, positive when discharging.	30775	FC03	int32	W	R
active_power_l1 AC active power on phase L1, positive when discharging.	30777	FC03	int32	W	R
active_power_l2 AC active power on phase L2, positive when discharging.	30779	FC03	int32	W	R
active_power_l3 AC active power on phase L3, positive when discharging.	30781	FC03	int32	W	R
grid_voltage_l1 AC grid voltage on phase L1, volts.	30783	FC03	int32	V	R
grid_voltage_l2 AC grid voltage on phase L2, volts.	30785	FC03	int32	V	R
grid_voltage_l3 AC grid voltage on phase L3, volts.	30787	FC03	int32	V	R
frequency AC grid frequency, hertz, typically 50 or 60.	30803	FC03	uint32	Hz	R
reactive_power_l1 Reactive power on phase L1, VAr reported in watt register.	30807	FC03	int32	W	R
reactive_power_l2 Reactive power on phase L2, VAr reported in watt register.	30809	FC03	int32	W	R
reactive_power_l3 Reactive power on phase L3, VAr reported in watt register.	30811	FC03	int32	W	R
operating_mode_for_active_power_limitation Encoded mode controlling how active power limitation is applied.	30835	FC03	uint32		R
battery_current DC battery current, amperes, positive during discharge.	30843	FC03	int32	A	R
soc Battery state of charge, 0 to 100 percent.	30845	FC03	uint32	%	R
current_battery_capacity Present usable battery capacity as a coded value.	30847	FC03	int32		R
battery_temperature Battery temperature measured at the inverter, degrees Celsius.	30849	FC03	int32	°C	R
battery_voltage DC battery pack terminal voltage, volts.	30851	FC03	uint32	V	R
power_supply_status Encoded status of the inverter power-supply subsystem.	30877	FC03	uint32		R
lowest_measured_battery_temperature Minimum battery temperature recorded over device lifetime, degrees Celsius.	30997	FC03	int32	°C	R
highest_measured_battery_temperature Maximum battery temperature recorded over device lifetime, degrees Celsius.	30999	FC03	int32	°C	R
max_occurred_battery_voltage Peak DC battery voltage recorded over device lifetime, volts.	31001	FC03	int32	V	R
allowed_charge_power Maximum charge power currently permitted by battery management, watts.	40189	FC03	uint32	W	R
allowed_discharge_power Maximum discharge power currently permitted by battery management, watts.	40191	FC03	uint32	W	R
set_active_power Active power setpoint; positive to discharge, negative to charge, watts.	40149	FC16	int32	W	W
set_control_mode Control mode selector; defines how power setpoints are interpreted.	40151	FC16	uint32		W
set_reactive_power Reactive power setpoint for grid management services, VAr.	40153	FC16	int32	W	W
grid_guard_code SMA Grid Guard unlock code; write to enable protected parameter changes.	43090	FC16	uint32		W
min_soc_power_on Minimum state of charge required to power on the inverter.	40705	FC16	uint32	%	W
min_soc_power_off State of charge threshold at which the inverter shuts down.	40707	FC16	uint32	%	W