Modbus TCP connection times out. What should I check?

Confirm that Modbus TCP is explicitly enabled in the SmartLogger under Settings, Comm. Param., Modbus-TCP. By default, the function is disabled. Also verify that the Gateway's IP address is listed in the allowed-client list if Enable(Limited) mode is active, and that no firewall blocks port 502.

Writes to battery mode registers return exception code 3. Why?

Exception code 3 (illegal data value) typically means the SmartLogger has not been configured for remote dispatch mode. Navigate to Settings, Battery Control on the SmartLogger WebUI and set the working mode to Charge/Discharge based on grid dispatch before writing to these registers over Modbus TCP.

Values written via Modbus revert after a timeout. What causes this?

The SmartLogger applies a scheduling timeout: if no updated setpoint is received within the configured interval, it falls back to a safe default. Ensure your ModbusCloud automation job writes setpoints at a frequency shorter than the SmartLogger's active power scheduling timeout, and set a sensible fallback power value in the SmartLogger EMS settings.

Is it safe to write arbitrary values to the battery setpoint registers?

Use caution with all write registers in this template. Sending out-of-range charge or discharge power values, or setting the reserve SOC below the battery's minimum, can trigger protection faults, reduce cell lifespan, or invalidate the battery warranty. Always verify permitted setpoint ranges in the Huawei SmartLogger Modbus interface documentation before writing values.

Free Modbus template: Huawei SmartLogger (battery)

The Huawei SmartLogger is a data collection and energy management gateway for PV and battery storage plants, connecting inverters, energy storage systems, and meters over Ethernet. This template targets the battery control interface of the Huawei SmartLogger via Modbus TCP, exposing six write registers that govern the battery operating mode, charge and discharge power setpoints, dispatch enable flag, charge target SOC, and minimum reserve SOC. Installers can use these registers to implement remote battery dispatch from the ModbusCloud Gateway without operating the SmartLogger web interface directly.

Name	Address	Function	Type	Unit	Access
batterymode_a Battery working mode setpoint, selects charge/discharge control strategy.	47100	FC16	uint16		W
batterymode_c Battery charge power setpoint, controls maximum charge rate.	47246	FC16	uint16	W	W
batterymode_d Battery charge/discharge enable flag, activates remote dispatch control.	47083	FC16	uint16		W
batterymode_e Battery discharge power setpoint, controls maximum discharge rate.	47249	FC16	uint32	W	W
batterymode_i Battery charge target SOC setpoint for timed or scheduled charging.	47247	FC16	uint32	%	W
batterymode_j Battery minimum reserve SOC setpoint, limits depth of discharge.	47087	FC16	uint16	%	W