The way the motor controller is currently hooked up, I have the throttle position sensor supplying a voltage to the speed control input of the inverter. The problem with this is that in all other cars, pressing on the accelerator gives more torque, not more speed. Some inverters will allow a torque input, but with my motor/inverter combination, that isn't possible. What my inverter does have, however, is an analog output that represents the current being given to the motor at any instant. If I connect an opamp with the positive input to the throttle position sensor and the negative input to the current output from the inverter, and feed the output of the opamp in to the speed control input, the throttle position sensor should control the current supplied to the motor. Current is related to torque, so this hack should make the car a lot more drivable.
I'll wait until it gets around the block under its own power to try this, though.
Sunday, August 10, 2008
I took a couple of days off of work to make a final push on getting the car rolling, and it paid off. I finished all the sheet metal work around the battery box, and gave it a shot of primer gray. I also finished up all the wiring. I used 3/4" flexible waterproof conduit run in the tunnel above the driveshaft and transmission from the battery box to the front of the car where the inverter lives. I got 70 cells (the remaining 28 are still being conditioned) and installed them:I was hoping to take it for a little spin with this partial pack, but 244 volts from these 70 cells was not enough to start up the DC-DC converters for the 12 volt system, and without 12 volts, the main contactor would not close, so no joyriding yet. I should get the remaining cells put in sometime this week.