Quarter completed in 8.168 @ 155.78 MPH -> Getting close to the magic 7’s.
Bill Dube - KillaCycle - April 4, 2007
We learn something new with every race. We made a bunch of spot-on modifications recently that made a huge difference in our performance for our latest runs down the strip at the All Harley Drag Racing Association (AHDRA) event on March 30th through April 1st. We vaporized all the existing EV drag racing records with a series of quicker and quicker record-breaking runs. On the last run of the event, we clocked 8.168 seconds at 155.78 MPH
>>> More Batteries!
We put in another 110 of the most powerful Li-Ion cells in the world to make a total of 990 A123 Systems
M1 cells in the bike. This pushed the power output to over 350 HP. We are now able to draw 1575 amps from the 375 volt, 7.5 kW-hr battery pack. There are just 161 lbs of cells in this pack. We call the A123 Systems
battery pack “Mister Fusion” because it acts like a bottomless pit of power and energy on the track. We could make 7 or 8 runs without recharging if we wanted. It only takes a few minutes to recharge the pack between runs, so we top it off every time. We only use about 700 w-hrs (about $0.10) of electricity for each round. This includes the burn-out and the more than 2 mile round trip back to the pits! Without these powerful A123 Systems
batteries, we would have no hope of setting new world records.
>>> Series/Parallel Shifting
Another change we made was to install a series/parallel contactor. The Zilla Controller
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.
>>> Pack Heaters
Another improvement we made was to build in Kapton heaters into the battery pack. We used these to bring the pack up to optimum temperature, (75 Celsius) and maintain it there for maximum power output. The A123 Systems cells are unique in that you can bring them to very high temperatures without damage. (They age a bit more quickly at high temperature, but that is it.)
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