Custom MQTT charger with phase switching via Shelly and Pulsar Plus

[hinge83]

Hi EVCC team 👋

I'm working on a custom charger setup and would love some input.

⚡ What I'm trying to do
I want to enable phase switching (1p/3p) using a Shelly relay in combination with a Wallbox Pulsar Plus charger. My goal is to:

Use EVCC (not Home Assistant) to decide when to switch phases.

Control phase switching via MQTT to the Shelly.

Continue using the Pulsar Plus as the actual EV charger.

🧩 What I've tried
I've configured a custom charger in evcc.yaml like this:

chargers:

• name: customMqtt
  type: custom
  status:
  source: mqtt
  topic: "ev/lader/status"
  charging: "charging"
  connected: "connected"
  disconnected: "disconnected"
  enable:
  source: mqtt
  topic: "ev/lader/enable"
  payload: true
  payloadOff: false
  maxcurrent:
  source: mqtt
  topic: "ev/lader/setCurrent"
  phases1p3p:
  source: mqtt
  topic: "ev/lader/phaseSwitch"
  payloads:
  1: "1"
  3: "3"
  tos: true

But I'm struggling to get this working. EVCC fails to start

🧪 What I'm looking for
✅ Is this setup supported the way I'm attempting it?

📐 Are there known working examples of phases1p3p with type: custom chargers?

🧠 How can I ensure EVCC is the decision-maker on when to switch phases?

🧰 Any best practices for combining template: pulsarplus with external phase switching?

Any help would be greatly appreciated – and thank you for a fantastic open-source project 🙏

[RenatusRo]

basically:
this is a bad, dangerous idea for electrical reasons.
and no software hack can fix this.

best practice is a manually operated switch for two of the 3 phases
https://hager.com/at/katalog/produkt/hab303-lasttrennschalter-3p-32a

[hinge83]

Hi,

Thanks for your comment. I would like to better understand why you believe it is dangerous to implement phase switching in this setup.

I am using a Shelly Pro 3 with mechanical relays that physically disconnect the circuits. In addition, I have configured an automation in Home Assistant that ensures there is no load on the charger before switching. The automation actively stops the charging session, waits 10 seconds after disconnection to guarantee a complete shutdown, and only then performs the phase switch.

Also, it is worth mentioning that the Wallbox Pulsar Max already supports automatic phase switching during solar charging, so the concept itself is already used in practice by certified manufacturers.

Given the physical disconnection and the load-free switching, could you please clarify what specific electrical risks you see remaining in this approach?
I am of course open to improving the setup if needed.

Best regards

[StefanSchoof]

Here is a longer discussion about the topic: #4763

[hinge83]

Hi StefanSchoof

Thanks for referring to the discussion. I completely understand that caution is necessary when switching phases.

However, it’s also worth noting that even a manual switch can theoretically interrupt a load if not handled properly, which could also be harmful to both the vehicle and the charger if done under active current flow.

In my setup, I have implemented a failsafe mechanism within Home Assistant:

Charging is stopped first.

A 10-second wait is enforced to ensure full current decay.

Charging status is checked to confirm that charging has indeed stopped.

Only then are the phases switched (off/on).

After another 10-second delay, charging is restarted.

This sequence is specifically designed to minimize risk and ensure safe conditions before and after any phase switching action.

Of course, physical manual switches provide additional visual verification and mechanical certainty, but with proper automation control and verification steps, I believe safe automated switching is achievable in a home environment.

Best regards