Electric Car Conversion

In November 2008 I picked up the idea of converting a regular ICE car to an electric car. The main reason was back then (and still is) a strong interest in the underlying technology. Therefor I didn't want to use existing products but roll my own. For propulsion I chose an industrial ACIM for its simplicity and availability. To drive such a motor from a battery pack, an inverter is needed. It converts DC current to a rotating 3-phase current which makes the motor spin.

I chose the LiFePo4 battery technology for it is currently the best compromise between cost, weight and power density and offers the best cycle life.

Like all lithium cells they need to be monitored for over and under-voltage. Therefor I developed a monitoring system that measures the voltage of every single cell and transmits that information wireless using infrared light pulses.

Over a timespan of 6 years I "built my dream" and got it approved by the German TÜV Nord. That means it also passed the EMC test i.e. a test that ensures that no other electronic equipment is disturbed by the car.

3 of those 6 years (part time, while attending a normal day job) I spent developing the inverter. Read up on the history on the diyelectriccar forum. I spent another year and a half building a prototype car and another year and a half building the actual car (VW Polo 86C) and developing the BMS. All that included the help of many others.

With all the materials ready and all the development done I'd estimate a conversion time of 2 weeks when converting the same or a very similar car. It's the unexpected and unknown that uses a lot of time: taking stuff apart again and again, waiting for parts to arrive etc.

I decided to make the inverter design available to everyone. AC inverters are considered complicated and mysterious. For that reason many people are scared away from the beautiful AC technology. I'm hoping that I can contribute a tiny bit to making inverters less mysterious.

You can build your own 3-phase motor controller with the material presented here. I'm also offering hardware kits that save you the trouble of ordering parts from different suppliers. You also support the development of the project by ordering a kit.