Have you ever wanted to own an electric car? or have you ever wanted to drive a Porsche 911? I wanted both, so I decided to build one. This blog is here to document my journey as I convert a 2002 Porsche 911/996 Carrera 2 from a gas guzzler to a completely electric vehicle - not a hybrid!

Tuesday, September 18, 2012

Charger high-power testing

I feel the charger is the most dangerous part of the car that I've built so far because it is based on an open source project, I built it from scratch, and I had to debug the software myself.  To build my confidence that things are working like they should, I've been carefully babysitting the charger while in use.  While testing the maximum power delivery of the charger, I wanted to keep a closer eye on the thermals of all the components in the charger box, so I borrowed a thermal imaging camera from the shop.  Here are some images during operation.

Above is the view of the charger box on the floor of the garage with all major components exposed. Below is the thermal data over the top of the charger at the end of a one hour, 18Ah delivered charge cycle.  The numbers shown are in degrees Celsius.  Each picture marks the Minimum and Maximum.

Below is a close up of the hottest part of the inductor during this charge cycle. This indicates to me I need to improve the inductor cooling with additional heat sinks and more airflow.
After I proved the 220VAC operation was OK, I moved the charger box into the car.  I also cranked up the power so the charger had full 220VAC @ 30Amps available to it.  The charger ramped up the duty cycle and peaked at 244VDC @ 27Amps = 6,588 Watts.  Not too shabby.  It ran for a few minutes, then abruptly shut down.  The user interface indicated it hit a thermal limitation and was pausing until it cooled down.  With the thermal camera I could see that the switching mosfet was heating up a lot faster with the higher current.  Below is a picture of the mosfet which is mounted directly to a massive heatsink.  You can make out the heatsink fins in the picture.  So what I learned here is that this area of the design also needs more airflow through the heatsink to maintain the high high current delivery.


  1. Great information. Keep up the good work. I ordered mine per assembled as I too was nervous about this aspect.

  2. You might consider putting the heat sink on the outside of the enclosure...

  3. Hey, I know its been a while but how's your charger doing? and how' the car?!