The motor turns too much

Original Article ↗ Hacker News Discussion ↗

Integrated EV Drivetrains and Chinese Cost Advantage

  • BYD’s “e-axle” (motor, inverter, diff, charger in one CAN-controlled module) seen as a major reason they can reuse hardware across models and undercut Western OEMs.
  • Debate over why Chinese EVs are cheaper:
    • One side: low Chinese wages, lax regulations, subsidies, tightly protected domestic market, and long-running state backing of EVs and batteries.
    • Other side: labor is a small share (often cited 5–15%) of car cost; key edge is early national push into EVs and LFP batteries, vertical integration, and faster innovation.
  • Disagreement on how much current per-car subsidies in China vs. US still matter; some argue US tax credits are now larger, others say true support levels are opaque.

Complexity of Modern EVs

  • Hyundai Kona example: many CAN buses, ~100+ ECUs, 10+ kg of low-voltage wiring; some find this “sad” given EVs could be simpler.
  • Counterpoint: similar complexity exists in ICE vehicles due to safety, infotainment, and comfort systems; not just the powertrain.
  • Some argue Tesla and Chinese newcomers started with cleaner-sheet EV designs but are now accumulating legacy complexity too.

Control Logic, Safety, and “Runaway” Behavior

  • Bench tests show Kona motor will spin to high RPM under tiny constant torque with no load or brake, including in “Neutral”.
  • Engineers in thread note:
    • Torque is very low (~5 Nm), easy to stop with brakes in a real car.
    • Under no-load, vector-controlled motors naturally ramp RPM if any nonzero torque is applied.
    • ABS sensors and safety standards (e.g., ISO 26262) are meant to make dangerous wheel-speed-sensor failures vanishingly rare.
  • Some remain uneasy that ECUs don’t explicitly detect “no vehicle inertia” cases; others say extra checks add complexity and new failure modes.

Human Factors and Unintended Acceleration

  • Long subthread on past ICE unintended-acceleration incidents:
    • Many cases attributed to driver error and panic, especially with automatics and older drivers.
    • Suggestions: shift to neutral, stand hard on brakes, or kill ignition—but several argue most drivers won’t think of this under stress.
  • Concern that increasing “drive-by-wire” (throttle, shift, sometimes brake/steer assist) moves more risk into software and human-interface design.

EV Conversions and Modularity

  • Converting ICE cars to EVs seen as technically difficult and often uneconomic:
    • Battery packaging, weight and suspension changes, torque vs. transmissions, accessory drives, heating, and regulatory approval are major hurdles.
  • Some niche success exists (classic cars, Tesla-salvage builds, open-source inverter projects), but it’s labor- and skill-intensive.
  • Several note that modern EVs are more like tightly coupled “eggs” than modular “onions,” making partial reuse of OEM drivetrains harder than expected.