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Borrowing from : KillaCycle - World’s quickest Electric bike while running A123System's M1 Cel's. [Archive] - CleanMPG Forums

>>> Series/Parallel Shifting < <<

Another change we made was to install a series/parallel contactor. The Zilla Controller (Cafe Electric llc) has the ability to operate a series/parallel motor contactor automatically. The motors are initially configured in series. Thus, the full controller output current travels through both motors. This gives maximum starting torque. As the motors spin up, the voltage across each of them increases. When that voltage matches the battery voltage, the current will decrease as motor rpm continues to increase. The Zilla will then switch the motors into parallel connection. This will double to voltage available to each motor, but will divide the current. The motors can turn much faster, but with half the torque. It result is just like shifting a transmission from low to high.

We could not get the contactor to shift automatically during the two runs we had on Friday test and tune session. The 60 ft times were fantastic, (1.169 seconds) but we were not getting the top-end performance we needed. We re-wired the launch button to be a manual shift button and this proved to work quite well for the rest of the weekend. We plan to upgrade the Zilla firmware and we believe this will solve the auto-shift problem.