Parent Inverter Modbus Register 81: Max Charge Current BMS

Technical Definition

The register Max Charge Current BMS at address 81 is used to monitor max charge current bms on the Parent Inverter.

• Protocol: Modbus RTU
• Data Type: U WORD
• Unit: A
• Access: Read Only

How to Read (Python pymodbus)

Use this code snippet to read this specific value via RS485:

from pymodbus.client.sync import ModbusSerialClient

client = ModbusSerialClient(method='rtu', port='/dev/ttyUSB0', baudrate=9600)
client.connect()

# Read Max Charge Current BMS (Address: 81)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=81, count=2, unit=1)

if not result.isError():
    print(f"Raw Value: {result.registers}")
else:
    print("Error reading register")

client.close()

Integration (Home Assistant)

Paste this into your configuration.yaml:

- platform: modbus_controller
  name: "Max Charge Current BMS"
  address: 81
  value_type: U_WORD
  unit_of_measurement: "A"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[Parent Inverter]

    PLC -- "A+ (D+)" --> Device
    PLC -- "B- (D-)" --> Device
    PLC -- GND --> Device

💡 Engineer's Insight

Analysis: Maximum allowed charging current specified by the Battery Management System (BMS), in Amperes (A).

Troubleshooting: Zero value suggests BMS communication error, disabled charging, or battery fault.