question

I dont have any experience with HASS but the register you are querying (842) will provide either a battery negative or battery positive value (+ for charging, - for consumption)

You may find MQTT easier to use as well. Not every measurement has a Modbus register. MQTT provides a much easier way to obtain the values and its structure is simple to follow.

Here is a python Modbus example

#!/usr/bin/env python3


from pymodbus.constants import Defaults
from pymodbus.constants import Endian
from pymodbus.client.sync import ModbusTcpClient as ModbusClient
from pymodbus.payload import BinaryPayloadDecoder

VEsystemID = 100

ip = "192.168.20.156" # ip address of GX device or if on venus local try localhost

# Local network ip address of Cerbo GX. Default port 502
client = ModbusClient(ip, port='502')

# All modbus variable requests are sent to this function and it return's the requested value
def modbus_register(address, unit):
    msg     = client.read_input_registers(address, unit=unit)
    decoder = BinaryPayloadDecoder.fromRegisters(msg.registers, byteorder=Endian.Big)
    msg     = decoder.decode_16bit_int()
    return msg

BatteryWatts  = modbus_register(842, VEsystemID)

print(f"BatteryWatts {BatteryWatts}")

Edit Feb 2024:

FYI the above is for the older pymodbus

here is one for the newer pymodbus

                  

                   
#!/usr/bin/env python3
                   


                   
from pymodbus.constants import Endian
                   
from pymodbus.client import ModbusTcpClient as ModbusClient
                   
from pymodbus.payload import BinaryPayloadDecoder
                   


                   
BmvID = 223
                   


                   
ip = "192.168.20.156"
                   


                   
client = ModbusClient(ip, port='502')
                   


                   
def modbus_register(address, slave):
                   
    msg     = client.read_holding_registers(address, slave=slave)
                   
    decoder = BinaryPayloadDecoder.fromRegisters(msg.registers, byteorder=Endian.BIG)
                   
    msg     = decoder.decode_16bit_int()
                   
    return msg
                   


                   
BatterySOC  = modbus_register(266, BmvID) / 10
                   


                   
print(f"BatterySOC {BatterySOC}")
                  

Thanks Elvis, Indeed in Python i managed to get the data in the right format. However, MQTT sounds prommising is there an example where i can work from?

Just use this:

https://github.com/sfstar/hass-victron

Okay, using the examples provided i got it working in Home assistant, if anybode interested i can post the yaml files. However, i still struggling reading the critical load from modbus anyone knows which register i should read? I used the excel but outside ID 100 i got reading exceptions. Exception Response(131, 3, GatewayPathUnavailable). also when i use a python script to read

Yes, please post your yaml files. I‘m currently struggling with the same issue.