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 A123Systems 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 A123Systems 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. With the latest PFC-50 charger from Manzanita Micro, we can recharge the bike in just 5 minutes! 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 A123Systems 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 serie/parallel motor contactor automatically. The motors are inititally configured in series. Thus, the full contoller 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.
These fantastic 60 ft times translate to a 0 to 60 mph time of 1.04 seconds.
>>> 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 A123Systems 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.)
>>>> Next Event < <<<
We will be displaying the KillaCycle at the Wired Magazine NextFest on September 13th – 16th in Los Angeles
We’ll be running exhibition passes at the NHRA Nationals at Las Vegas Motor Speedway on October 25th – 28th
Here is a link to a video of one of the record-breaking runs at Firebird Raceway:
Here is a link to a fantastic article about the KillaCycle in Designfax On-line