Monday, March 3, 2014


Step 36:  Rewire BMS current sensor and test heater.  In step 29 I mentioned that I needed to rewire the new school current sensor so that it would work better.  I did this using proper shielded cable and it no longer gets stuck.  Now I can log some driving and hone my efficiency.  

There are 2 routes I can take to work, one via highway 71 which is mosly 55+ mph, and one via Barton Creek which is mostly 35 mph.  The Barton Creek route is ~1 mile and a few minutes longer but 18% more efficient going to the office and 5% more coming home.  In addition to the speed I think other differences are stop sign or stop light placement with respect to the bottom of hills (bad!).

I was also able to test my heater.  It draws 900W from the battery and appears to increase energy per mile by 12% (reduce range by 12%).  It was in the mid-twenties and the heater kept the car warm enough that I wasn't freezing but there is room for improvement.  It was a strange sensation to smell electric heat in a car.

Notice the peak powers on the heater run are lower than the other runs.  That's because the battery was near freezing and cell resistance goes up with cold.  So its harder to get the amps out and I have to drive in a higher gear to get the same speed.

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