Electric Shifter Kart


The goal of this project is to turn used EV parts into something fun to drive. It owes a lot to what we had learned a few years ago on the Bremsthesis, which had a ton of power but very little of anything else. The other objective is to document the process of tuning an interior PM motor. These motors have a ton of advantages, including easier drive, better high speed performance, and unlimited top speed*, but also come with their own set of nuances.

It is one of the first vehicles built out of used EV parts that has done anything interesting (most other attempts have not gotten past the 'it moves' stage). We've seen 0.9g peak acceleration; the theoretical peak acceleration of the vehicle is an absurdly high 2.5g with a 70 kg driver, which we cannot achieve with the current weight distribution and tires. Characterizing top speed is a little trickier - we have achieved 60 mph, but because IPM's field weaken well, on the current pack the top speed is probably closer to 75-80 mph (power limited). At the rated motor top speed (16,000 RPM) the vehicle speed is around 120 mph, which is entirely achievable on elevated voltages (the whole power system is good for 400V), but probably not a good idea in Cambridge.

The specs are:
  • Motor: 2x Hyundai Sonata HSG, total 85 ft-lbs (115 Nm) @ 0-2,500 RPM, 40 HP (30 kW) @2,500-10,000 RPM on 160V nominal.
  • Traction pack: 42S 2P lithium polymer, total 168 V peak 8.0Ah.
  • Transmission: 4:1 (80t/20t) 15mm Gates Polychain GT Carbon.
  • Motor controller: custom field-oriented control; control stage: STM32F446RE, power stage: 2nd-gen Prius power module + capacitor. 
*not actually true, but explaining this in detail requires math

The documentation is split into a series of posts, currently consisting of:

Hardware
Theory

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