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:


1 comment:

  1. Hey, i read your kart project with the HSG motors and was thinking about making a cheaper version of that EV.
    GM made a system like the HSG in 2007-2009, called BAS. It was simply an alternator that was wired to 36V and used NiMH batteries.
    One of those BAS motors costs around 50-80USD looking in the car-part(dot)com website, but shipping to my country is 4x their own price(200USD), so i would like to see if you and your team could take a look in my idea and maybe test it.
    50USD in the alternator, 50USD in a VESC (3-12S 50A continuous), and since 12-14V standard alternators can run at 48V on stator without problems, maybe those 36V alternators could be ran at 96V or 120V, after installing hall sensors or a sin/cos resolver and checking thermals.