twc3simulator (Tesla Wall Connector 3 Simulator)

Fakes the API responses of a real Tesla Wall Connector 3, using live current, energy, and network data pulled from a Tasmota smart plug wired into the circuit. It doesn't control anything — it's a read-only stand-in that lets software expecting a "real" TWC3 (like evcc or Home Assistant) work with a Tesla Universal Mobile Connector (or any other dumb charger) instead.

Credit

This is a fork of laenglea/twc3simulator — all credit for the original idea and implementation goes to @laenglea, who built this after finding evcc had no way to control charging through a Universal Mobile Connector.

What this fork adds

I basically just wanted my UMC to display in Home Assistant. This fork extends langlea's original idea to work with Home Assistant's Tesla Wall Connector integration, which polls a few endpoints beyond what evcc needs.

• /api/1/version — static device identity (firmware/part/serial number). HA's config flow reads these during setup and fails if the endpoint is missing.
• /api/1/lifetime — cumulative energy, sourced from the Tasmota device's own running total (Status 0 → StatusSNS.ENERGY.Total), converted from kWh to Wh.
• /api/1/wifi_status — Wi-Fi connection details, sourced from the Tasmota device's own network status (Status 0 → StatusSTS.Wifi and StatusNET) rather than static placeholders — since the Tasmota is the thing actually connected to your network, its real signal strength, IP, and MAC are more honest than making something up.

All three reuse a single Status 0 call to the Tasmota device rather than hitting it separately per endpoint.

Requirements

• A Tasmota outlet or smart relay, connected to your dumb charger of choice. I use a Sonoff POWR320D (20 amp) relay, flashed with Tasmota.

• To extract a temperature value for pcba_temp_c, your Tasmota device will require an on-board temperature sensor. In my case, the POWR320D has this, which can be enabled by running: curl "http://tasmota_ip/cm?cmnd=SetOption146%201". Your mileage may vary.

Installation

This fork isn't published as a prebuilt image — build it from source.

Clone it to the machine you want to run it on:

git clone https://github.com/lits101/twc3simulator.git

Then build and run via docker compose:

services:
  twc3sim:
    container_name: twc3sim
    build: ./twc3simulator
    environment:
      - "TASMOTA_IP=10.10.10.10"
    ports:
      - "80:80"
    restart: unless-stopped

where TASMOTA_IP is the IP of the Tasmota device the current/energy/wifi information should come from.

Or build directly from GitHub without a local clone:

services:
  twc3sim:
    container_name: twc3sim
    build: https://github.com/lits101/twc3simulator.git#main
    environment:
      - "TASMOTA_IP=10.10.10.10"
    ports:
      - "80:80"
    restart: unless-stopped

You can also include environment variables for the serial number and part number of your UMC, and these will be passed through to Home Assistant if specified.

environment:
  - SERIAL_NUMBER=<your UMC2's actual serial number>
  - PART_NUMBER=<your UMC2's actual part number>

Validate

if it's running properly you should get something back when looking at each of:

http://<ip>/api/1/vitals
http://<ip>/api/1/lifetime
http://<ip>/api/1/version
http://<ip>/api/1/wifi_status