JK BMS in Home Assistant, the simple way

Why not Bluetooth?

Bluetooth integrations work, but the BMS often sits in a metal cabinet in a garage, far from any proxy, and Bluetooth connections drop. RS485 is a wired link built for exactly this job. MoniWatt for JK BMS takes the wired route and hands the data to Home Assistant over Wi-Fi.

Sensors you get

• sensor.jkbms_monitor_soc, …_voltage, …_current, …_power
• sensor.jkbms_monitor_cell_01_voltage … one per cell
• sensor.jkbms_monitor_cell_delta, …_cell_min, …_cell_max
• sensor.jkbms_monitor_balance_current and binary_sensor.jkbms_monitor_balancing
• sensor.jkbms_monitor_mos_temperature, …_temperature_1, …_temperature_2
• binary_sensor.jkbms_monitor_alarm

Useful automations

• Delta above 40 mV at more than 3.45 V per cell: notify, the pack may need a top balance.
• MOS temperature above 60 °C: reduce inverter output or switch on a fan.
• SOC below 20% at night: shed non-essential loads.
• Balancer running for more than three hours in a row: flag a cell to inspect.

JSON API

GET http://moniwatt.local/api.json?key=YOUR_KEY

{
  "soc": 91, "voltage": 54.42, "current": 6.1,
  "cells": [3.402, 3.401, 3.405, 3.398, ...],
  "delta_mv": 7, "balancing": true, "balance_current": 0.6,
  "mos_temp": 31.0, "temps": [22.4, 22.9], "cycles": 87
}