Optimizing EV Charging via PV Surplus: Sigenergy System Integration Advice (go-e Gemini vs. Sigen EVAC)

Energy
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Hi everyone,

I am looking for architectural and hardware advice on setting up an automated EV charging system that prioritizes excess solar production (PV surplus charging). I want to dynamically shift my car's charging rate based purely on what my panels are exporting, while balancing the house load and my home battery storage state of charge (SOC).

My Current Setup:

  • Solar/Storage: Sigenergy Hardware Stack (5.9 kWp PV array, hybrid inverter, and 9 kWh battery storage).
  • Home Automation: Home Assistant fully integrated with the system locally using the TypQxQ/Sigenergy-Local-Modbus integration via HACS. I have clean, local, real-time readouts of plant PV power, load power, grid export, and battery SOC.
  • The Car: A 2026 Tesla Model Y Standard (18" wheels, handles up to 11 kW AC 3-phase charging).

The Dilemma:

I am torn between two completely different directions for the EV charger and want to know if anyone has implemented either with a Sigenergy stack:

  1. The Native Route (Sigenergy EV AC Charger - Sigen EVAC):

    • Pros: It communicates directly with my existing inverter/BESS via the mySigen app. The app handles "PV Surplus Charging" natively without me having to build custom templates or automations.
    • Cons/Questions: Does this lock me out of manual overrides or fine-tuning inside Home Assistant? If I expose the EVAC via the Modbus integration (select.ac_charger_work_mode), do I retain fast, snappy control over starting/stopping or forcing grid charging during cheap tariff hours?

  2. The Smart Agnostic Route (go-e Charger Gemini):

    • Pros: Widely praised in the local control community for its open HTTP API, MQTT support, and budget-friendly price point.
    • Cons/Questions: Because it won't talk directly to the Sigenergy inverter, I will have to build the brain in Home Assistant. I’ll need an automation (or an add-on like evcc / EMHASS) to constantly read sensor.plant_export_power and dynamically scale the go-e's charging amperage.

My Questions for the Community:

  1. Has anyone successfully automated a third-party charger like the go-e Gemini using the real-time local Modbus data coming off a Sigenergy system? Does the Modbus data stream fast enough (1-5s intervals) to prevent pulling heavily from the home battery when clouds pass?
  2. If you went with the native Sigen EVAC charger, does the native "AI/PV Surplus" mode inside the mySigen app play nicely with a home battery? (e.g., does it protect the 9 kWh home battery from being accidentally emptied into the car)?
  3. Does the native Sigen EVAC allow smooth phase-switching (1-phase to 3-phase) automatically when solar generation crosses the minimum 3-phase threshold (~4.1 kW), or does it scramble the charging logic?

Would love to hear from anyone running a similar configuration!

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I've recently started using this: https://github.com/InventoCasa/PV-Excess-Control external component. Forum Link: ☀️ PV Excess Control: Solar Excess Optimizer as a HACS Integration (successor of the pyscript blueprint)

I'm using it to control multiple chargers for a diy home battery bank giving priority to a Powerwall3 battery that was installed with the solar_system and is also my inverter. In the few days I've used PV Excess Control it I've been very happy with it. I added my EV charger (OpenEVSE) as the lowest priority load today but I need to tweak it as I watched it today and I may not have used the right entities for AC current control.

In the 5 day's I've been using it I've only imported about 430W from the Grid. so it is handling shedding the loads when clouds come.

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