DC or AC?

Most electric cars built by hobbyists (see http://www.austinev.org/evalbum/ for a nice collection of home-built and other electric vehicles) run on DC - direct current. It's pretty simple - get a bunch (4-15) of batteries, hook them together, and run a motor with it. Speed/torque control is done by limiting the current through the motor by an electronic chopper (Pulse Width Modulation). AC systems, on the other hand, need higher voltage (300 Volts DC for a 240 Volt motor, or around 600 Volts DC for a 480 Volt motor) This means a string of 26 batteries to run a 240 Volt motor. Also, instead of a single switch to control current, as in the DC case, AC motor drives need to have 6 switching transistors and a bunch of digital signal processing logic to produce the three sine waves needed to run a 3 phase motor. AC Propulsion and Siemens and a few others make automotive-type AC drives. See http://acpropulsion.com/ and http://metricmind.com/for examples. These go for about $20k, so they're quite out of most hobbyists' reach. So why bother with an AC conversion?

• Pure snobbery
• Simpler, more efficient motors
• Regenerative braking
• Higher voltage means lower current, which means lighter wires and other components

An interesting industrial-component AC system from Australia is here:
http://www.austinev.org/evalbum/1149