EVCC

Use the TAG ID from the Joulo API to let evcc identify which vehicle is charging

evcc identifies a vehicle by the RFID card or token that started the session. Joulo returns that value as id_tag on every session. Read it once from the API and put it in evcc.yaml as the vehicle's identifier.

The dashboard generates this recipe with your token filled in under Developer → API → Recipes.

When this works

evcc only sees an identifier when it talks to the charger itself. That is the case when:

evcc is the OCPP backend of the charger, and Joulo receives the frames through evcc, or
Joulo is the OCPP backend and forwards every frame to evcc. Set evcc's wss:// address as the External OCPP backend on the charger in the dashboard under Laadstations.

A charger that only talks to Joulo gives evcc nothing to match. The id_tag then still shows what card started each session, but evcc cannot use it.

Read the TAG ID

Start a charging session

Plug in the car and start the session with the card or app you normally use.

Read the active session

curl -s -H "Authorization: Bearer YOUR_API_TOKEN" \
  https://api.joulo.nl/functions/v1/api/chargers \
  | jq -r '.chargers[].current_session.id_tag // empty'

GET /sessions returns the same field per past session, so an earlier session works too.

Add it to evcc.yaml

vehicles:
  - name: tesla
    type: template
    template: tesla
    identifiers:
      - "04A1B2C3D4E5F6"   # the id_tag from step 2

evcc then knows which car is on the charger and applies that vehicle's charge plan.

Home Assistant

If you already run the Home Assistant sensors, the value is in sensor.joulo_active_tag_id. No curl needed.

id_tag is not always a physical card. A charger that starts sessions itself reports its own placeholder, such as a serial number. See the Session.id_tag description on the sessions endpoint page.