Sigenergy ESS Max Charging/Discharging Limit Entities Not Writable

[discipleofnagash]

Hey, I have the following problem when setting up my integration - this is a summary from Claude Code:

number.sigen_plant_ess_max_charging_limit and number.sigen_plant_ess_max_discharging_limit cannot be written to. They remain stuck at 0.0 kW despite:

Being enabled in the entity registry
Having set_value_fn defined in code
Automations triggering successfully
Manual Developer Tools → Services calls
What We Verified

No inverter-level alternatives - Only plant-level entities exist for these limits (checked code + modbus register definitions)
Entities are enabled - disabled_by: null in entity registry
Write function exists in code (number.py):
set_value_fn=lambda coordinator, _, value: coordinator.async_write_parameter(
"plant", None, "plant_ess_max_charging_limit", value
)
Modbus register defined (modbusregisterdefinitions.py):
"plant_ess_max_charging_limit": ModbusRegisterDefinition(
address=40032,
count=2,
register_type=RegisterType.HOLDING, # Should be writable
data_type=DataType.U32,
gain=1000,
unit=UnitOfPower.KILO_WATT,
applicable_to=["hybrid_inverter"],
)
Other entities work:

• select.sigen_plant_remote_ems_control_mode - writable ✓
• number.sigen_plant_grid_export_limitation - holds value (10.0 kW)
• number.sigen_plant_ess_charge_cut_off_state_of_charge - holds value (100%)

I tried to set this via:

automation
UI
Developer tools

Note, when trying to set the value, I did set the Mode to an appropriate selection beforehand, e.g. Command Discharging (PV First) and then tried to update number.sigen_plant_ess_max_discharging_limit.

I am trying to enable this for integration with PredBat

[Q-Claw]

Thanks for the detailed report — this is super helpful. Could you please share complete debug logs for one full write attempt so we can pinpoint where it fails?

What to capture

1. Enable debug logging for this integration:

logger:
  default: info
  logs:
    custom_components.sigen: debug

2. Restart Home Assistant.
3. Perform one write test (set number.sigen_plant_ess_max_charging_limit or ...discharging_limit) from Developer Tools.
4. Wait ~20–30 seconds so refresh/readback finishes.
5. Post the full log section from just before the service call until after refresh completes.

Please include in your message

• Exact entity id written
• Value sent
• Whether Remote EMS / control mode was enabled at that moment
• Inverter model + firmware version

We’re specifically looking for lines showing:

• register write target (40032 / 40034)
• encoded write value
• Modbus write response or exception
• immediate readback value after refresh

With that full trace we can confirm whether this is a write failure, mode/firmware gate, or readback/persistence behavior.

[Q-Claw]

Good point — for logging steps, please follow the existing guide here: #54

For this specific issue, please also include:

1. exact entity written (number.sigen_plant_ess_max_charging_limit or ...discharging_limit)
2. value you sent
3. approximate timestamp of the write attempt
4. whether Remote EMS / control mode was enabled at that moment

That will make it much easier to correlate write + readback in the debug log.

[discipleofnagash]

Hi, weirdly it now works when attempting to run the updated test, I have no idea why!

Test performed:

• Entity: number.sigen_plant_ess_max_charging_limit
• Value sent: 8 kW
• Result: SUCCESS - value changed from 10.0 → 8.0

Conditions when it worked:

• Remote EMS: ON (switch.sigen_plant_remote_ems_controlled_by_home_assistant = on)
• Control mode: Maximum Self Consumption

Debug logs:
Writing plant parameter 'plant_ess_max_charging_limit' (slave: 247)
with value 8.0 to address 40032 (type: HOLDING, data_type: U32, gain: 1000)
Encoded values: [0, 8000]

Inverter:

• Model: SigenStor EC 12.0 SP
• Firmware: V100R001C22SPC112B071P

[TypQxQ]

That's why I would need complete logs for debugging.