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!

Sunday, July 15, 2012

Blowing fuses

When I changed my battery pack from 2 parallel strings with 54 series cells each to one string of 96 series cells, I had to beef up the battery charging plan.  The charger I was building could not handle the higher output voltage required to charge 96 cells in series.  The solution was to purchase a PFC 1st stage that could boost the DC output voltage to ~380V.  In order to charge 96 cells @ 3.65VDC, I need to reach 350VDC which is now possible.  When the PFC stage arrived, it motivated me to finish up the charger portion.  I was able to complete the wiring and get the Arduino programmed with the latest open source software from EMotorWerks.com.  When I applied 13VDC to the input, I was able to wake up the digital circuits and start setting parameters via the simple user interface on the color LCD.  From there it was time to test the AC input.  I applied 120V AC from the wall outlet, the box started to hum for a few seconds, then I blew a fuse.  I ended up blowing 4 fuses that day while trying to isolate the problem area.  In the end, the dual rectifier + 16 capacitor board does not like its outputs tied together from the separate banks of capacitors.  At the moment I'm stuck on this simple physics problem and will have to debug this further soon.  A side affect of all the brute force testing is one of the current limiting input resistors (20W 1ohm) blew up... So I'll need another one of those.  Below is a picture of the problematic sub-assembly.

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