Sunday, August 29, 2010

E-transmission part 2 testing begins

We got the bike back on the road and i did the first test ride and the results are interesting.
The goals of this experiment were two fold
  1. The main goal was to better match the C rate of the batteries to the motor, reducing locked rotor amps. Essentially impedance matching the motor to the batteries, without question this goal was achieved. What this means is from a standstill to about 30 MPH half the current is needed when in 604 mode to achieve the same torque as a 602 two turn motor. Then at 30 MPH I drop the throttle flip a switch and continue in 602 mode. The controller has no problems with the switch from four turn to two turn and back again. 
  2. The second goal was more of a hopeful goal being even better performance, this  is yet to be obtained. Electric motors are interesting animals and very different than there ICE counterparts. While a ICE engine build power with RPM electric engines have most of their torque at the low end of the RPM range. I was Reving out the 604 mode before switching to the 602 mode and from 20 MPH to 30 the performance dropped as the motor became voltage starved. To really test performance I should have switch out of the 604 into the 602 much earlier. To do this fast enough to realize a performance benefit shifting really has to be fast and probably automatic. I believe there is performance to be had as long as no time is wasted shifting. With 100 volts of battery the max top speed in four turn mode is 35 MPH
Actively switching from a four turn motor to a two turn motor works and results in a reduced starting current off the line. An active impedance matched motor reduces the peak current demand on the batteries allowing a peak of 2.5C instead of 5C for the same performance one would get with the standard 602 two turn motor. Also there is less controller switching and less high order harmonics wasting heat in the motor. Performance gains have yet to be measured.


  1. I know it is a long time ago since you investigated this. But why did you choose to switch between two different set of windings instead of switching between star and delta on the same set of windings?