BMS-EV — Home Assistant

BMS-EV controllers publish native MQTT auto-discovery. Home Assistant finds the battery on its own and builds the entities — there is no custom component to install and nothing to configure by hand.

Full documentation: docs.bms-ev.com

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Setup

1. In the controller's web interface, set your MQTT broker address, username and password.
2. Make sure Home Assistant uses the same broker (MQTT integration).
3. That's it. The device appears under Settings → Devices & Services → MQTT within a few seconds.

The controller publishes to homeassistant/sensor/…/config, the discovery prefix Home Assistant listens on by default. It registers itself as a device (manufacturer BMS-EV), so every entity lands under one device page rather than scattered across your entity list.

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Entities

Discovered automatically:

Battery

Entity	Unit	Notes
State Of Health	%	reported by the vehicle's own BMS
Battery Voltage	V	pack terminal voltage
Battery Current	A	charge positive, discharge negative
Stat Batt Power	W	instantaneous power
Battery Total Capacity	Wh
Battery Remaining Capacity (real)	Wh	as reported by the pack
Battery Remaining Capacity (scaled)	Wh	after the configured SoC window
Battery Charged Energy	Wh	cumulative
Battery Discharged Energy	Wh	cumulative

Cells

Entity	Unit	Notes
Cell Max Voltage	V	highest cell in the pack
Cell Min Voltage	V	lowest cell
Cell Voltage Delta	V	spread — the number to watch for pack health
Balancing Active Cells	count	how many cells are balancing right now
Balancing Status	text
Individual cell voltages	V	one entity per cell, disabled by default

Per-cell entities are registered but disabled by default — a 96-cell pack would otherwise add 96 entities to your recorder. Enable the ones you want in the device page.

Temperature

Entity	Unit
Temperature Min	°C
Temperature Max	°C
CPU Temperature	°C

Limits and state

Entity	Unit	Notes
Battery Max Charge Power	W	limit the BMS currently allows
Battery Max Discharge Power	W
BMS Status	text
Pause Status	text
Emulator Status	text	controller state
Event Level	text	active fault severity

Diagnostics

Free Heap, Largest Heap Block — useful when reporting an issue.

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Dashboard

A starting point, using entities exactly as discovered. Replace bms_ev if your controller uses a different MQTT topic name.

type: vertical-stack
cards:
  - type: gauge
    entity: sensor.bms_ev_state_of_health
    name: State of Health
    min: 0
    max: 100
    severity:
      green: 80
      yellow: 70
      red: 0

  - type: glance
    entities:
      - entity: sensor.bms_ev_battery_voltage
        name: Voltage
      - entity: sensor.bms_ev_battery_current
        name: Current
      - entity: sensor.bms_ev_stat_batt_power
        name: Power

  - type: history-graph
    hours_to_show: 24
    entities:
      - sensor.bms_ev_cell_min_voltage
      - sensor.bms_ev_cell_max_voltage

  - type: entities
    title: Pack health
    entities:
      - entity: sensor.bms_ev_cell_voltage_delta
        name: Cell delta
      - entity: sensor.bms_ev_temperature_min
        name: Coldest cell
      - entity: sensor.bms_ev_temperature_max
        name: Hottest cell
      - entity: sensor.bms_ev_balancing_active_cells
        name: Cells balancing

Energy dashboard

Battery Charged Energy and Battery Discharged Energy are cumulative, so they can feed Home Assistant's Energy dashboard directly:

Settings → Dashboards → Energy → Add battery system, then pick those two entities for energy going in and out of the battery.

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Alerts worth setting up

Cell delta is the single most useful number for spotting a pack going out of balance:

automation:
  - alias: "Battery cell imbalance"
    trigger:
      - platform: numeric_state
        entity_id: sensor.bms_ev_cell_voltage_delta
        above: 0.1
        for: "00:10:00"
    action:
      - service: notify.persistent_notification
        data:
          title: "Battery cell imbalance"
          message: >
            Cell voltage spread is
            {{ states('sensor.bms_ev_cell_voltage_delta') }} V.
            A widening spread usually means one cell is ageing faster than the rest.

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If the device doesn't appear

Check	How
Controller reaches the broker	Its web interface shows the MQTT connection state
Same broker on both sides	Home Assistant's MQTT integration must point at the same host
Discovery enabled in HA	On by default; if you turned it off, the device will not appear
Messages arriving	mosquitto_sub -h <broker> -t 'homeassistant/#' -v should show config messages

The controller republishes its discovery messages periodically, so a Home Assistant restart is enough to pick it up again — you do not need to re-flash anything.

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Manual configuration

Auto-discovery covers everything above, so hand-written sensors are rarely needed. examples/mqtt_sensors.yaml is kept for unusual setups — a separate broker, a filtered bridge, or a controller on firmware older than 16.5.0.

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Related

• bms-ev-mqtt-examples — MQTT topics, Node-RED, Grafana, InfluxDB
• bms-ev-docs — compatibility dataset: 70 battery profiles × 56 inverters
• docs.bms-ev.com — full technical documentation

Built on dalathegreat/Battery-Emulator.