With the increasing number of EVs on the roads, many questions arise in society, e.g. where all those electric cars will be charged, will our distribution network handle it, etc…
I asked myself the first question after I bought my first electric car, the VW e-UP. Maybe I had more time to think, because the delivery of the car took about half a year :-)
I'm one of the lucky ones who have their own garage on the estate, so I planned to charge the car in it. In order not to have to charge the car via a 230V schuko socket, it was necessary to introduce a three-phase connection. For a more favorable charging price, I set up a double tariff at the distributor.
Subsequently, I deduced the criteria for the wallbox from this:
- enable charging during a low tariff
- enable the setting of the charging limit in kWh (to charge the battery in my e-Up to 80%)
- implementing RCM in the wallbox, as the B-type RCCB is quite expensive
- use ESP32 (I gained experience with it from my previous project)
At first I started to design an evse board with full functionality, only later I found out that it is probably more appropriate to design a simple board with an ESP32 devkit for development https://oshwlab.com/dzurik.miroslav/esp32-devkit-evse. And after testing the basic functionality, to design a board with full functionality with the ESP WROOM module. I needed a total of 8 ADC inputs (control pilot, proximity pilot, 3x ac voltage, 3x current transformer) but the ESP32 ADC1 has only 6 inputs available. So I chose the ESP32-S2, which has more inputs (there was no ESP32-S3 at the time). The design of the resulting board is here https://oshwlab.com/dzurik.miroslav/esp32s2-diy-evse, the dimensions are such that it fits into the UM122 case.
Both boards using same firmware (one source code, but different build because ESP32 and ESP32-S2 had different instruction sets). The source code is not hard-coded on the GPIO or other hardware design features, but reads the hardware configuration from a configuration file that is on a separate partition. You can read more about the firmware on the github repository https://github.com/dzurikmiroslav/esp32-evse.
My wallbox is housed in a cheap plastic wiring box, it could easily have a fixed charging cable (as it is housed in its own garage), but I wanted to try out the handling of socket lock... It also has a Nextion HMI display and a LoRaWAN module for recording telemetry data. You can read more on github wiki https://github.com/dzurikmiroslav/esp32-evse/wiki/ESP32-S2-DA