Why does the soc register always return zero or no data?

The SAJ H1 Series requires a Wi-Fi or LAN communication module such as the eSolar AIO3 to expose Modbus TCP on port 502. If the module is absent, not powered, or not joined to the local network, register reads will fail. Confirm the module has a valid IP, that port 502 is open, and that the unit ID in the portal matches the module configuration.

Power register values look implausible. What should I check?

The power register at address 16550 is a signed int16, so values near 32767 or below zero indicate charging direction or overflow. SAJ inverters typically apply a scale factor documented in the Modbus protocol PDF; verify the scaling divisor in your portal sensor configuration. Raw counts divided by the wrong factor will produce readings that appear too large or too small.

The Gateway connects but the battery-mode write registers have no effect.

The batterymode registers use function code 16 (write multiple registers). Confirm the ModbusCloud Gateway has write permission enabled for this template. Some firmware versions of the SAJ H1 Series require writes to be sent to a specific unit ID. Also verify that the operating mode you are attempting to set is supported by the battery protocol selected in the inverter's settings menu.

Is it safe to write battery-mode setpoints remotely without supervision?

Use caution. Writing incorrect values to the batterymode registers (addresses 12871, 13828, 13830, 13831, 13832) can change how the inverter charges or discharges the battery, potentially overriding protection settings or violating battery warranty conditions. Always test setpoint changes during low-demand periods, keep a record of the original values, and confirm the inverter returns to expected behaviour before leaving the site.

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Registers (8)

3 read / 5 write

Name	Address	Function	Type	Unit	Access
power Instantaneous battery power, signed, positive discharge negative charge.	16550	FC03	int16	W	R
energy Cumulative battery energy throughput, unsigned 32-bit counter.	16597	FC03	uint32	Wh	R
soc Battery state of charge, 0 to 100 percent.	16495	FC03	uint16	%	R
batterymode_a Battery operating mode setpoint, register variant A.	12871	FC16	uint16		W
batterymode_d Battery operating mode setpoint, register variant D.	13828	FC16	uint16		W
batterymode_e Battery operating mode setpoint, register variant E.	13830	FC16	uint16		W
batterymode_f Battery operating mode setpoint, register variant F.	13831	FC16	uint16		W
batterymode_g Battery operating mode setpoint, register variant G.	13832	FC16	uint16		W