All registers return NaN. What is causing this?

Some inverter implementations include the Model 124 block for compatibility but populate all registers with NaN values when no battery is physically connected or licensed. Confirm a battery storage unit is installed, commissioned, and reporting to the inverter before expecting valid readings in this model.

Scale factor registers return negative values. Are my readings wrong?

No. SunSpec scale factors are signed integers used as powers of ten. A value of -1 means divide the raw register value by 10, -2 means divide by 100. Always multiply the raw register value by 10 raised to the scale factor before displaying the result. The ModbusCloud portal applies this automatically when the template is configured correctly.

InWRte and OutWRte writes are accepted but the inverter ignores them.

Write setpoints in Model 124 only take effect when StorCtl_Mod is set to activate the corresponding mode: bit 0 for charge control, bit 1 for discharge control. Write the required bitfield value to StorCtl_Mod first, then confirm the ChaGriSet register permits the intended charging source. Also verify the inverter web interface has remote Modbus control enabled.

Is it safe to write InWRte, OutWRte, or WChaMax repeatedly from automation?

Use caution. Some inverter manufacturers explicitly warn that cyclically writing non-exempt RW registers can wear the device flash memory. Use the InOutWRte_RvrtTms reversion timeout so setpoints expire safely rather than issuing continuous writes. Always test write operations in a controlled environment and consult the specific inverter documentation before deploying automated setpoint changes.

Free Modbus template: SunSpec Model 124 — Storage

Name: SunSpec Model 124 — Storage
Brand: SunSpec
SKU: 4c52fdc9-0d25-4d63-908e-c40a0a4c6073

SunSpec Model 124 is the Basic Storage Controls model defined by the SunSpec Alliance, used to monitor and control battery storage systems connected to compatible hybrid and storage inverters over Modbus TCP. The template reads charge state, available capacity, and internal battery voltage, and exposes read-write setpoints for maximum charge power, charge and discharge ramp rates, minimum reserve percentage, and charge/discharge power windows via InWRte and OutWRte. The StorCtl_Mod bitfield activates or deactivates charge and discharge modes at the inverter. Importing this SunSpec Model 124 template into your ModbusCloud portal delivers immediate visibility and remote control of battery storage behaviour across any SunSpec-compliant device.

Registers (26)

26 read / 12 write

Name	Address	Function	Type	Unit	Access
id SunSpec model identifier; fixed value 124 for Basic Storage Controls.	0	FC03	uint16		R
l Length of the model block in registers, excluding header.	1	FC03	uint16		R
wchamax Maximum charge power setpoint in watts; reference value for rate calculations.	2	FC03	uint16	W	R/W
wchagra Maximum charge ramp rate as a percentage of WChaMax per second.	3	FC03	uint16	% WChaMax/sec	R/W
wdischagra Maximum discharge ramp rate as a percentage of WChaMax per second.	4	FC03	uint16	% WChaMax/sec	R/W
storctl_mod Storage control mode bitfield; bit 0 enables charge, bit 1 enables discharge.	5	FC03	bool		R/W
vachamax Maximum apparent power for charging, in volt-amperes.	6	FC03	uint16	VA	R/W
minrsvpct Minimum state-of-charge reserve setpoint as a percentage of WChaMax.	7	FC03	uint16	% WChaMax	R/W
chastate Current charge state as a percentage of amp-hour rating.	8	FC03	uint16	% AhrRtg	R
storaval Available storage capacity, in amp-hours, above the minimum reserve.	9	FC03	uint16	AH	R
inbatv Internal battery DC voltage in volts.	10	FC03	uint16	V	R
chast Enumerated battery charge status: off, empty, discharging, charging, full, holding, or testing.	11	FC03	uint16		R
outwrte Discharge power setpoint as a percentage of WDisChaMax; negative limits discharge range.	12	FC03	int16	% WDisChaMax	R/W
inwrte Charge power setpoint as a percentage of WChaMax; negative limits charge range.	13	FC03	int16	% WChaMax	R/W
inoutwrte_wintms Time window in seconds before InWRte or OutWRte change takes effect.	14	FC03	uint16	Secs	R/W
inoutwrte_rvrttms Reversion timeout in seconds; after expiry, InWRte and OutWRte revert to defaults.	15	FC03	uint16	Secs	R/W
inoutwrte_rmptms Ramp time in seconds over which InWRte or OutWRte transitions to the new setpoint.	16	FC03	uint16	Secs	R/W
chagriset Grid charging permission: 0 = PV only, 1 = grid charging allowed.	17	FC03	uint16		R/W
wchamax_sf Scale factor (power of ten) applied to the WChaMax register value.	18	FC03	int16		R
wchadischagra_sf Scale factor applied to WChaGra and WDisChaGra register values.	19	FC03	int16		R
vachamax_sf Scale factor applied to the VAChaMax register value.	20	FC03	int16		R
minrsvpct_sf Scale factor applied to the MinRsvPct register value.	21	FC03	int16		R
chastate_sf Scale factor applied to the ChaState register value.	22	FC03	int16		R
storaval_sf Scale factor applied to the StorAval register value.	23	FC03	int16		R
inbatv_sf Scale factor applied to the InBatV register value.	24	FC03	int16		R
inoutwrte_sf Scale factor applied to InWRte and OutWRte register values.	25	FC03	int16		R