This is the backend for an amperimeter sensor. It is a simple REST API that allows storing amperimeter readings from an electric circuit to perform later analysis on them.
This project was built originally to both allow us at home to see quickly over wifi if any powerful devices were simultaneously connected at home, and later to also automatically use any remaining power budget to charge an EV we own, but delaying the charge if no power budget is available.
We originally thought about creating an EVSE for that matter, but we found out that for our EV platform, the car allows setting any amperage as low as 0A in 1A increments, so we decided to implement this functionality as a Rocket fairing here instead of hacking 1-phase dumb EVSE to support ISO 15118-2 XML messages.
For that matter we can rely on a cheapo $60 dumb 16A EVSE charger.
The amperimeter sensor can be built with a simple ACS712 sensor or a SCT013 sensor, and a ESP32 or similar microcontroller. The ESP32 should send the amperimeter readings to this backend using the following format:
curl -X POST -H "Content-Type: application/json" -d '{"amps": 10.0, "watts": 2200.0}' http://localhost:8000/log/$TOKEN/
The backend will store the readings in a SQLite database and will allow querying the readings to perform analysis on them.
It will also automatically query the Tessie API to check if the car is nearby the charger and is charging. If it is, the backend will automatically increase or decrease the amperage requested by the car to match the power budget available.
All these options can be set up in the Rocket.toml file.