We turned an old Tesla charger into a smart wallbox
The 2019 Tesla Wall Connector can do just one thing: send power to the car. With Energostat it now charges from the sun, follows the home battery's state of charge and works without the cloud. We didn't change the wallbox at all.
A dumb wallbox, a smart car
The second-generation Tesla Wall Connector is a reliable bit of kit, but it knows nothing about what's happening on the roof. Plug in the cable and it charges flat out, up to 11 kW on three phases, whether the sun is shining or not. A new smart wallbox with installation costs tens of thousands of Czech crowns.
The idea: decide in the car, not in the wallbox
A Tesla can be controlled over Bluetooth, just as when you unlock it with your phone. Energostat, our own control unit next to the inverter, pairs with the car as a key with permission to control charging. It sets the current anywhere from 5 to 16 A, and starts and stops charging.
The wallbox simply supplies the power; Energostat makes every other decision. No internet, and no Tesla cloud.
How it works in our own home
The house runs on three Victron MultiPlus-II inverters and goes off-grid over the summer. Energostat monitors how much energy is flowing into the home battery and, when there's a surplus, raises the car's charging current step by step. By our measurements, one amp across three phases equals 671 W. When the surplus drops, it lowers the current again.
It keeps a reserve in the home battery for the night and watches each phase separately. When the washing machine's heating element switches on, it cuts the car's current before the inverter can be overloaded.
Specifications
| Component | Solution |
|---|---|
| Wallbox | Tesla Wall Connector Gen 2 (2019), 3-phase, 16 A |
| Range | 5–16 A, i.e. 3.45–11 kW |
| Car control | Bluetooth, local, no cloud |
| Control | Energostat + Victron |
What you get
You charge the car with your own electricity instead of exporting it to the grid for pennies. There's no need to buy a new wallbox. The app shows why the car is or isn't charging at any given moment, and you can set a target such as "80% by 7:00".
Have a Tesla and a Victron solar system? Get in touch. There's more about the box on the Energostat page.
