Homemade Type 2 Wall-Box


We bought last summer a commercially available electric car (an additional EV besides the converted E-Mini). After some discussions we have selected a BMWi3 as our family car. The i3 is really convenient to drive and easy to handle – the drawbacks are the limited range and the rather high price.
As a standard charging possibility we got 230V-cable (only) which limits the charging power to 1.9kW (single phase on a 10A socket). It takes more than 15 hours to fully charge the 30kWh battery. I decided therefore to make a homemade wall-box which allows to charge the car with a maximum power of 11kW – this reduces the charging time to 3.5 hours. Why homemade? On one hand I wanted to get familiar with the corresponding charging possibilities and on the other hand because wall-boxes are quite expensive (about 800 € – without the installation) compared to the built-in components.

Insides Type2 Charging Station
Built-in Components

The Type 2 is an European specified charging plug/process for electric vehicles (IEC 62196 Typ 2 & SAE J1772). The communication between the charging station (power capability) and vehicle is done through a simple PWM signal and connected resistors on EV and charging -station side. There is no serial bus communication involved (no CAN nor Ethernet, .. …). Small printed circuit boards (EVSE Wall-Box) doing the corresponding PWM can be bought for about 70€ in the internet with the corresponding manuals how to wire the entire box. All you need besides the small print is a suitable contactor (able to switch the max. power), a box and a charging plug with cable. I was able to make the box for about 300€.
The wall-box has a switch which allows to choose between 10A or 16A loading current. The contactor is designed to switch higher loads but the supply in my garage is for a max current of 16A (T25 Swiss socket with 3x400V and 16A which results in 11kW power level).

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