Power Electronics

The high voltage traction electronics system consists principally of the motor controller. It is supported by a main fuse and circuit breaker, as well as a main contactor (relay) that is a critical safety device to cut-off power at the drivers command in case of malfunction. Also attached to the high voltage system is a DC/DC converter which efficiently steps-down the voltage to 14V to charge the auxiliary battery and power both the motor controller’s computer circuits and all the conventional loads in the car. The motor controller also requires human-interface wiring for ignition and dashboard lights, as well as a throttle sensor. Since the Zilla is water-cooled I installed a reservoir, radiator and pump to circulate coolant through its built-in water-block.

  

  

All the traction system wiring is done in 2/0 welding cable. The long runs connecting the rear batteries to the front is the same 2/0 cable run in plastic corrugated tubing conduit for extra protection. A Heinemann 250A circuit breaker is mounted on the side of the front rack and electrically disconnects the pack in the middle of the series string. It is most often used as a “power switch” for storing or working on the car.

While I have used the same motor controller (Zilla 1KLV) the whole time, I completely rebuilt the HV wiring and supporting systems once incorporating many revisions from the first version.

The first revision used a Kilovac contactor (white plastic, cylindrical) and a IOTA DLS battery charger as DC/DC converter. The charger circuit and DC/DC feed are protected with class J fuses. A hall effect current sensor is placed in the circuit for a PakTrakr meter.

  

The second revision changed to an Albright contactor based on advice that I had gotten that they are more durable. Since the contacts are open, if they weld shut it’s possible to pry them back apart and file the contacts, where the Kilovac is junk. In order for the Kilovac contactor to meet its peak specifications it requires a lot of heat-sinking through the high current terminals as well. I switched the IOTA DC/DC out for a new one from Belktronix as the IOTA was blowing through fuses- as it turns out its inrush limiting went- it still works fine but pulls a huge current spike upon hookup. I switched to “midget size” 10×38 size fuses for a more compact fuseblock- the fuses are Ferraz Shawmut A60Q series which are rated 600V AC/DC. I ditched the PakTrakr which never really worked very well and installed a large shunt for a CycleAnalyst meter. I switched from short lengths of 2/0 cable interconnects to solid copper bars that I bent and twisted to fit- turns out that heavy stranded cable gets very inflexible in short lengths once crimp lugs are attached! Finally I fabricated a clear plastic shield to fit over the whole assembly.

  

  

  

The Zilla is outfitted with the HEPA (hall effect pedal assembly) option- when I was planning the car I decided that I would like to keep the original accelerator pedal though- I ended up cutting the pedal off the HEPA module and attaching the arm to the original accelerator up under the dashboard.