Webasto Next / Unite for Home Assistant

Monitor and control Webasto Next and Ampure / Webasto Unite wallboxes in Home Assistant over Modbus TCP, with an optional REST API connection for extras such as LED control and firmware diagnostics.

This is a community-maintained integration. It is not affiliated with, endorsed by, or supported by Webasto, Ampure, or the Home Assistant project.

Supported hardware

• Webasto Next — fully supported in the current release.
• Ampure / Webasto Unite — fully supported since v1.2.0. The Unite uses a different register layout (telemetry on input registers, a few rescaled/widened registers, plus a three-phase switch); pick Webasto / Ampure Unite in the model selector during setup. Confirmed on firmware 3.156 and 3.187 (#37).

The wallbox must be reachable over Modbus TCP (default port 502). The REST API features additionally need the wallbox web-interface credentials.

Features

• Local polling over Modbus TCP through an async update coordinator.
• Sensors for charge point and charging state, currents, power, energy, session data, fault codes and EV limits.
• Controls: dynamic charging current, fail-safe current and timeout, and start/stop/keep-alive buttons.
• A Connected binary sensor that reports reachability even while the wallbox is offline (useful in automations).
• Services for current limit, fail-safe, charging sessions and keep-alive frames.
• Optional REST API integration: LED brightness, free-charging toggle and tag ID, firmware/diagnostics sensors and a restart button.
• Device triggers (charging started/stopped, connection lost/restored, keep-alive sent) and ready-to-use blueprints.
• Automatic "Life Bit" keep-alive handling and resilient reconnect with back-off, so a power-cycled or still-booting wallbox recovers on its own.
• Tested against a virtual wallbox simulator.

Requirements

• Home Assistant 2026.5.1 or newer (requires Python 3.14.2). On older Home Assistant, stay on release 1.1.5.
• A supported wallbox (see Supported hardware) reachable over Modbus TCP.

Installation

HACS (recommended)

Or add it manually:

1. In HACS, open the three-dot menu and choose Custom repositories.
2. Add https://github.com/tomwellnitz/Webasto-Next-Modbus with category Integration.
3. Install Webasto Next and restart Home Assistant.

To test upcoming changes, enable Show beta versions on the integration in HACS.

Manual

1. Copy custom_components/webasto_next_modbus/ from this repository into your Home Assistant config/custom_components/ directory.
2. Restart Home Assistant.

Removal

1. Go to Settings → Devices & Services → Webasto Next / Unite, open the ⋮ menu on the entry and choose Delete. This removes the device, its entities and stored credentials.
2. If you installed via HACS, optionally remove the repository from HACS; for a manual install, delete custom_components/webasto_next_modbus/. Restart Home Assistant.

Configuration

Before you start: enable Modbus on the wallbox

Modbus TCP is disabled by default on the Webasto Next / Unite. Enable it first in the wallbox web interface: switch to the expert/installer view, then turn on Modbus TCP (default port 502). Without this the integration cannot connect (#36).

1. Go to Settings → Devices & Services → Add Integration and search for Webasto Next.
2. Enter your wallbox details:
   • Host — IP address or hostname (e.g. 192.168.1.50).
   • Port — default 502.
   • Unit ID — default 255.
   • Model — Webasto Next (default) or Webasto / Ampure Unite. Existing installs stay on Next; pick Unite for an Ampure / Webasto Unite (see Supported hardware — the Unite uses a different register layout).
   • Variant — your hardware power rating (11 kW or 22 kW).

The wallboxes do not advertise themselves on the network, so they are added manually by IP address; there is no auto-discovery.

The host, port, unit ID and entry name can be changed later without removing the integration via Settings → Devices & Services → Webasto Next / Unite → ⋮ → Reconfigure. Model, variant, scan interval and REST settings live under ⋮ → Configure.

Optional: REST API

The REST API exposes features that are not available over Modbus (LED control, free charging, firmware info, diagnostics, restart).

1. Open the integration entry → three-dot menu → Configure.
2. Enable REST API features and enter the wallbox web-interface credentials (username default admin).

Credentials are stored in the Home Assistant config entry and redacted from downloaded diagnostics. If the wallbox later rejects them, Home Assistant starts a guided reauthentication dialog so you can enter new ones; the Modbus side keeps working regardless. The wallbox's web interface uses a self-signed certificate, so the integration disables TLS verification for that local HTTPS endpoint.

Data updates

• Modbus telemetry is polled every 10 seconds by default. The interval is configurable via ⋮ → Configure → Scan interval.
• REST API data (firmware info, LED brightness, free charging, diagnostics, active errors) is fetched every 60 seconds. If the wallbox's web interface is unreachable at startup, the integration retries the REST connection every 5 minutes until it succeeds; the Modbus side is independent and keeps working.
• The "Life Bit" keep-alive runs continuously in the background: the integration writes 1 to the keep-alive register and polls until the wallbox clears it to 0, preventing the wallbox from dropping into fail-safe mode. The cadence follows the wallbox's own clear-cycle.

Entities

Modbus (always available)

Platform	Entities
Sensors	Charge point state, charging state, EVSE state, cable state, fault code, per-phase current and power, total energy, session energy and times, EV current limits, smart-vehicle detection.
Numbers	Charging current limit (0–32 A), fail-safe current (6–32 A), fail-safe timeout (6–120 s).
Buttons	Start charging, Stop charging, Send keep-alive.
Binary sensors	Connected (device_class: connectivity), Charging (device_class: battery_charging).

REST API (when enabled)

Platform	Entities
Sensors	Comboard/Powerboard firmware (SW & HW), plug cycles, error counter, signal voltages L1/L2/L3, active errors.
Numbers	LED brightness (0–100 %).
Switches	Free charging.
Text	Free charging tag ID.
Buttons	Restart wallbox.

Services

All services live under the webasto_next_modbus domain.

Service	Description
set_current	Set the dynamic charging current (0–32 A).
set_failsafe	Set the fail-safe current (6–32 A) and optional timeout (6–120 s).
start_session	Start a charging session.
stop_session	Stop the active charging session.
send_keepalive	Send a keep-alive frame manually.

REST API services (when enabled):

Service	Description
set_led_brightness	Set the LED brightness (0–100 %).
set_free_charging	Enable or disable free charging.
restart_wallbox	Restart the wallbox.

The "Life Bit" keep-alive is handled automatically in the background to keep the wallbox out of fail-safe mode; send_keepalive is only needed for manual control.

Automations and blueprints

Ready-to-import blueprints live under Settings → Automations & Scenes → Blueprints:

• FastCharge / FullCharge control — start or stop charging from input_boolean toggles.
• Charge target (kWh) — charge a set amount of energy, then stop.
• Charge until full — stop automatically once charging power drops below a threshold.
• Solar surplus optimizer — adjust the charging current to grid export to maximise self-consumption.
• Event notifications — send a mobile notification on wallbox events (charging started/stopped, connection lost/restored, keep-alive sent, cable connected/disconnected, fault occurred).

Device triggers for charging start/stop, connection state, cable connected/disconnected and fault occurred are available for your own automations.

Custom YAML example

For fully custom logic the integration's services and device triggers are usable directly. Replace <your wallbox device id> with the device ID from Developer Tools → States → your wallbox (or pick it interactively in the automation editor).

automation:
  - alias: Webasto — cap charging current at night
    triggers:
      - trigger: time
        at: "23:00:00"
    actions:
      - action: webasto_next_modbus.set_current
        data:
          amps: 6

  - alias: Webasto — fault alert
    triggers:
      - trigger: device
        domain: webasto_next_modbus
        device_id: <your wallbox device id>
        type: fault_occurred
    actions:
      - action: notify.mobile_app_my_phone
        data:
          title: Webasto fault
          message: "Fault code {{ trigger.event.data.fault_code }}"

Known limitations

• One Modbus client at a time — the Webasto Next / Unite accepts only one Modbus TCP connection. If another client (EVCC, a manual modbus: block, another HA add-on) is holding the slot, this integration cannot connect.
• Modbus is off by default on the wallbox — it must be enabled once in the wallbox web interface (expert / installer view) before setup will succeed (#36).
• No auto-discovery — the wallboxes do not advertise themselves over mDNS / zeroconf, so they are added manually by IP address or hostname.
• Use a static address — configure a DHCP reservation or use a hostname so the wallbox stays reachable; if the address changes, run the integration's Reconfigure flow.
• Unite three-phase switching is firmware-dependent — the holding register used by the switch (405) is not in the vendor's Modbus spec. Switching and read-back are confirmed on firmware 3.187 (#37); on other Unite firmwares the behavior is unverified.
• REST API uses a self-signed certificate — TLS verification is disabled for the wallbox's local web interface (required by the embedded HTTPS endpoint). REST credentials are stored in the config entry and redacted from diagnostics.
• Optional registers vary by firmware — registers a given firmware doesn't implement are auto-detected and dropped from the read plan; the corresponding entities become unavailable rather than spamming errors.
• Firmware downgrades are blocked by the vendor — community reports indicate Webasto does not allow rolling back to an older firmware once updated (#37).
• One device per config entry — to manage several wallboxes, add the integration multiple times (one config entry per wallbox).

Troubleshooting

• Cannot connect — verify host, port (502) and unit ID (255), and that the wallbox is reachable. Make sure Modbus TCP is enabled on the wallbox (expert view) — it is off by default. These wallboxes also accept only one Modbus TCP connection at a time, so make sure no other client (e.g. EVCC) holds it.
• Values stuck or stale — check the logs; transient errors are retried automatically, and a booting wallbox recovers on its own within a few minutes.
• Diagnostics — integration entry → three-dot menu → Download diagnostics (secrets are redacted).

See docs/support.md for more.

Development

uv sync            # install dependencies
uv run pytest      # run the test suite
uv run ruff check . # lint

A virtual wallbox simulator lets you develop without hardware. See docs/development.md and docs/architecture.md.

License and credits

Released under the MIT License. Thanks to @cdrfun for the advanced-blueprint inspiration, and to the contributors on #37 for the Unite register readouts.