Modbus setup prerequisite

There are two different SunSpec Model Types for Modbus: "int + SF" and "float":

All registers mentioned in this article refer to the SunSpec Model Type "int + SF".

I have added the following lines to configuration.yaml so that Home Assistant can connect to the Modbus interface.

modbus:
  - type: tcp
    # Put your Gen24 IP address here
    host: 192.168.1.137
    port: 502
    name: gen24
    sensors:
      - name: reading_battery_settings
        slave: 1
        count: 24
        address: 40345
        scan_interval: 5
        data_type: custom
        structure: ">10H2h4H8h"

The sensor "sensor.reading_battery_settings" reads all relevant Modbus registers and serves as the basis for the template sensors mentioned later:

From the sensor "reading_battery_settings", the individual values can be extracted via a value_template:

Source / Inspired by: github.com/bigramonk/byd_charging and forum.iobroker.net/topic/65205/modbus-fronius-gen24

change the charging behavior: Changing BYD Charging

The settings are changed via Modbus registers.

Relevant Modbus registers for controlling the charging behavior

These 4 registers are essentially relevant for controlling the battery:

{% set storCTL_mod= states('sensor.reading_battery_settings').split(',')[3] | int%}
{{ "in" if storCTL_mod == 1 else
"out" if storCTL_mod == 2 else
"in and out" if storCTL_mod == 3 
else "auto"  }}

{{ states('sensor.reading_battery_settings').split(',')[5]|int / 100 }}

{{ states('sensor.reading_battery_settings').split(',')[10]|int / 100 }}

{{ states('sensor.reading_battery_settings').split(',')[11]|int / 100 }}

So that the registers in HA can be displayed individually, I have created a template sensor for each of the registers in the "Settings", "Helpers" menu: "BYD.StorCTL_Mod", "BYD.MinRsvPct","BYD.OutWRte", "BYD.InWRte". The content for the template sensor can be taken from the previous table.

I have created scripts for the individual actions so that several registers can be adjusted in one process:

Home Assistant scripts

Set loading settings to default

The following tabs set the loading behavior to the default values:

A script can be used to set the registers: "Settings", "Automations & scenes", "Scripts", "ADD SCRIPT":

Content:

alias: Reset charging
sequence:
  - service: modbus.write_register
    data:
      slave: 1
      address: 40348
      value: 0
      hub: gen24
  - service: modbus.write_register
    data:
      address: 40355
      slave: 1
      value: 10000
      hub: gen24
  - service: modbus.write_register
    data:
      slave: 1
      address: 40350
      value: 500
      hub: gen24
  - service: modbus.write_register
    data:
      address: 40356
      slave: 1
      value: 10000
      hub: gen24
mode: single
icon: mdi:home-battery

Set SoC (lower charge limit) to 30%

To keep a little more reserve capacity in the battery, the default values can be adjusted slightly by setting the value for MinRsvPct to e.g. 3000 for 30% charge reserve. The value set via Modbus competes with the settings in the Fronius web interface: the higher value wins:

The following registers set the charging behavior to the default values with 30% charging reserve (SoC):

A script can be used to set the registers: "Settings", "Automations & scenes", "Scripts", "CREATE NEW SCRIPT":

Contents:

alias: Reset charging 30%
sequence:
  - service: modbus.write_register
    data:
      slave: 1
      address: 40348
      value: 0
      hub: gen24
  - service: modbus.write_register
    data:
      address: 40355
      slave: 1
      value: 10000
      hub: gen24
  - service: modbus.write_register
    data:
      slave: 1
      address: 40350
      value: 3000
      hub: gen24
  - service: modbus.write_register
    data:
      address: 40356
      slave: 1
      value: 10000
      hub: gen24
mode: single
icon: mdi:home-battery

Charging the battery from the mains

To charge the battery independently of the current power consumption or the current PV power, the following 3 registers can be set as follows. I have created an input helper in advance so that the charging power can be changed via the Lovelance dashboard:

Integrated in the dashboard, the charging power can be conveniently adjusted in the interface:

Here are the necessary tab settings for forced charging:

alias: Force charging
sequence:
  - service: modbus.write_register
    data:
      slave: 1
      address: 40348
      value: 2
      hub: gen24
  - if:
      - condition: template
        value_template: >-
          {{ states('sensor.reading_battery_settings').split(',')[6] |int(0) *
          10** states('sensor.reading_battery_settings').split(',')[20]|int(0) <
          10 }}
    then:
      - service: modbus.write_register
        data:
          address: 40355
          slave: 1
          value: 55536
          hub: gen24
    else:
      - service: modbus.write_register
        data:
          address: 40355
          slave: 1
          hub: gen24
          value: >-
            {{ 65536 - (states('input_number.charging_power')|int(0) /
            states('sensor.reading_battery_settings').split(',')[0]|int(1) *
            10000) | int }}
  - service: modbus.write_register
    data:
      slave: 1
      address: 40350
      value: 9900
      hub: gen24
mode: single
icon: mdi:battery-charging

Limit charging power

To limit the charging power to the previously created helper, the following registers can be set via another script:

alias: Charge-limit
sequence:
  - service: modbus.write_register
    data:
      address: 40356
      slave: 1
      hub: gen24
      value: "  {{ (states('input_number.charging_power')|int(0) / states('sensor.reading_battery_settings').split(',')[0]|int(1) * 10000) | int }}"
  - service: modbus.write_register
    data:
      slave: 1
      address: 40348
      value: 1
      hub: gen24
mode: single
icon: mdi:battery-charging

Discharging (forcing) the battery with a certain power

Here are the necessary register settings for forced discharging:

alias: ForceDischarge
sequence:
  - service: modbus.write_register
    data:
      address: 40356
      slave: 1
      hub: gen24
      value: >-
        {{ 65536 - (states('input_number.charging_power')|int(0) /
        states('sensor.reading_battery_settings').split(',')[0]|int(1) * 10000)
        | int }}
  - service: modbus.write_register
    data:
      address: 40355
      slave: 1
      value: |-
        {{ (states('input_number.charging_power')|int(0) /
         states('sensor.reading_battery_settings').split(',')[0]|int(1) * 10000) | int
         }}
      hub: gen24
  - service: modbus.write_register
    data:
      slave: 1
      address: 40348
      value: 3
      hub: gen24
mode: single
icon: mdi:home-battery

Examples

The following examples are taken from the Fronius documentation: 42,0410,2649.pdf and have been supplemented with the register numbers for use:

Only allow charging of the energy storage

This behavior can be achieved by limiting the maximum discharge power to 0% => results in window [-3300 W, 0 W]

Source: 42,0410,2649.pdf

Only allow discharging of the energy storage device

This behavior can be achieved by limiting the maximum charging power to 0% => results in window [0 W, 3300 W]

Allow neither charging nor discharging

This behavior can be achieved by limiting the maximum charging power to 0% and limiting the maximum discharging power to 0% => results in window [0 W, 0 W]

Source: 42,0410,2649.pdf

Charging and discharging with a maximum of 50% of the nominal power

This behavior can be achieved by limiting the maximum charging power to 50% and limiting the maximum discharging power to 50% => results in window [-1650 W, 1650 W]

Source: 42,0410,2649.pdf

Charging in the range from 50% to 75% of the nominal power

This behavior can be achieved by limiting the maximum charging power to 75% and limiting the maximum discharging power to -50% => results in window [1650 W, 2475 W]

The battery status in Fronius Solar.web changes to "Forced recharge"

Source: 42,0410,2649.pdf

Discharging with 50% of the nominal power

This behavior can be achieved by limiting the maximum charging power to -50% and limiting the maximum discharging power to 50% => results in window [-1650 W, -1650 W] 44

Source: 42,0410,2649.pdf

Charging with 50% to 100% of the nominal power

This behavior can be achieved by limiting the maximum discharge power to -50% => results in window [1650 W, 3300 W]

The battery status in Fronius Solar.web changes to "Forced recharge"

Source: 42,0410,2649.pdf

Use in practice: Home Assistant - Automation

In order to keep a residual capacity of 30% in the battery in winter and thus be able to use the PV point in an emergency and also not waste any battery capacity, I have come up with the following automation: 

The automation as YAML code:

alias: Batterie Management
description: ""
trigger:
  - platform: numeric_state
    entity_id:
      - sensor.byd_battery_box_premium_hv_ladezustand
    above: 99
    id: voll
  - platform: numeric_state
    entity_id:
      - sensor.byd_battery_box_premium_hv_ladezustand
    above: 30
    id: 30p
  - platform: time
    at: "03:00:00"
    id: Nacht
condition: []
action:
  - if:
      - condition: trigger
        id:
          - voll
    then:
      - service: script.reset_byd_charging
        metadata: {}
        data: {}
  - if:
      - condition: trigger
        id:
          - 30p
    then:
      - service: script.reset_charging_25
        data: {}
  - if:
      - condition: trigger
        id:
          - Nacht
      - condition: numeric_state
        entity_id: sensor.pv_remaining_today
        above: 20
    then:
      - service: script.reset_byd_charging
        metadata: {}
        data: {}
mode: single

The sensor for the PV forecast comes from the Forecast.Solar integration.

For details on the automations, see: Home Assistant automation - possibilities & basics

Sources

• Inspired by: github.com/bigramonk/byd_charging
• forum.iobroker.net/topic/65205/modbus-fronius-gen24
• Fronius documentation: www.fronius.com/~/downloads/Solar%20Energy/Operating%20Instructions/42,0410,2649.pdf

See also

• Fronius Gen24 commissioning: Connection > Setup > Connection
• Fronius Data & settings via network (Modbus)
• All about Home Assistant: Commissioning + Integration + Operation