Failsafe HEMS Use Case with Keba p30 and Watchdog + Shelly/Tasmota

[heresiarch]

I have a Keba WV p30x with a Shelly Mini 1 Gen4 with Tasmota firmware connected to X1 contact of the Keba.
On the Tasmota Device runs a simple Rule which sets the Relay to OFF, if no Heartbeat is received within 60 seconds. This will disable the Wallbox charging (X1 contact could be configured that way).
I would like to run the watchdog from within evcc (simple HTTP url to the tasmota device.)
So I could make sure that if connection to evcc is lost, the wallbox will be off. Watchdog requests will be stopped. So that I have always a failsave behavior. It would also be great, if EEBUS communication to controlbox is not working or an EEBUS LPC limit below a value like 4200W is active, that the watchdog stops. This is what the script is doing (iobroker): https://github.com/FernetMenta/ioBroker.eebus-go/blob/main/doc/manual-lpc-example.js
What is the evcc way for such a use case?

[heresiarch]

I created a dummy charger in evcc.yaml that sends a regular heartbeat to Tasmota.

This works for the following use cases:

1. Normal operation

   • evcc regularly sends Event heartbeat=1.
   • The Keba X1 contact stays closed.
   • Charging is possible.
   • This already works as expected.

2. Connection to evcc is lost

   • The Event heartbeat=1 heartbeat stops.
   • The Tasmota failsafe opens the Keba X1 contact.
   • Charging is stopped.
   • This already works as expected.

3. EEBUS LPC limit is below a threshold

   • If the current EEBUS LPC limit is below, for example, 4.2 kW,
   • I want to send POWER1 OFF instead of the heartbeat.
   • This should open the Keba X1 contact and prevent charging.

The Problem

I need to access the currently active EEBUS LPC limit from my scripting logic.

The logic I need is essentially:

if LPC limit < 4.2 kW:
    send "POWER1 OFF"
else:
    send "Event heartbeat=1"

How can I access the current EEBUS LPC limit value in the scripting logic in evcc.yaml?

Is there a way to retrieve or expose the currently active LPC value so that I can use it in this logic?

I don't see another way to implement this behavior, but I don't know how to access the current LPC value from the scripting logic.

chargers:
  - name: tasmota-watchdog
    type: custom
    status:
      source: const
      value: C
    maxcurrent: # dummy 
      source: js
      script: |
        var res = 8;
        2 * res; // returns 16
    enabled:
      source: const
      value: true
    enable:
      source: watchdog
      timeout: 60s
      initial: 1
      set:
        source: http
        uri: "http://192.168.178.6/cm?cmnd=Event%20heartbeat%3D1"
        method: GET
        auth:
          type: basic
          user: "admin"
          password: "XXX"
        timeout: 5s
``