HN Debrief

Renault: Electric motors with no rare earths

  • Hardware
  • Climate
  • Infrastructure
  • Europe
  • Supply Chain

Renault’s post explains its rare-earth-free EV motor as an electrically excited synchronous motor, or EESM. Instead of a permanent magnet rotor, it uses an electromagnet whose field is supplied through slip rings. That lets Renault avoid neodymium and other rare earth materials that dominate many permanent magnet synchronous motor designs. The basic reaction was that this is not some exotic new machine. It is a familiar trade. You remove scarce magnet materials and add control complexity plus some moving electrical hardware.

If you build or source EV hardware in Europe, this is less about a clever motor trick than a strategy to get out from under Chinese rare-earth leverage. Treat rare-earth-free motors as a cost, supply, and industrial-policy choice first, not an across-the-board performance upgrade.

Discussion mood

Mostly positive and pragmatic. People liked the supply-chain logic and recognized the motor as a real industrial choice, but there was little sense that Renault had revealed a breakthrough. The mood was that this is sensible engineering with clear tradeoffs, not magic.

Key insights

  1. 01

    Mass-market EVs change the comparison

    Comparing Renault’s 160 kilowatt motor to BMW’s 300 kilowatt unit misses the product target. Renault is building for roughly €20K vehicles, not luxury EVs, so the right question is whether a rare-earth-free motor can hit acceptable cost and performance in the lower end of the market. That makes BMW less a direct benchmark than a proof that the architecture can improve and trickle down.

    Benchmark this against the price band you sell into, not the flagship spec sheet. If you operate in budget EVs, watch for when higher-end rare-earth-free designs become cheap enough to migrate into entry platforms.

      Attribution:
    • bgarbiak #1
    • PedroBatista #1
    • nine_k #1
  2. 02

    The real penalty is mechanical, not electrical

    Powering the rotor electromagnet does not appear to be a giant efficiency tax. Commenters said the excitation draw is only a small slice of total motor power. The more important cost is added hardware. Slip rings and brushes are wear items, and the rotor becomes heavier and less mechanically robust. That is the trade that limits power density and long-term simplicity.

    When evaluating rare-earth-free motors, focus diligence on durability, maintenance, and packaging rather than assuming the main loss is energy consumption. Ask suppliers for wear data on slip rings and for real-world service expectations.

      Attribution:
    • cyberax #1
    • hnav #1
  3. 03

    This is an ex-China supply-chain move

    Several comments connected EESMs to a wider European and Indian supply-chain strategy built around avoiding Chinese rare-earth dependence. In that view, Renault, BMW, Nissan, and suppliers like ZF, Valeo, MAHLE, Schaeffler, AEM, Sona Comstar, and Sterling are not just picking a motor topology. They are aligning on a manufacturable alternative that fits new trade and sourcing constraints.

    If your roadmap touches automotive components in Europe or India, expect sourcing decisions to increasingly reflect trade policy and export controls. Supplier selection now has to account for political resilience, not just cost and efficiency.

      Attribution:
    • alephnerd #1 #2
  4. 04

    Sodium-ion looks better for storage first

    The idea of pairing rare-earth-free motors with sodium-ion batteries sounded appealing on cost and materials, but commenters argued the battery side is not ready for mainstream EV adoption. Sodium-ion still lags lithium iron phosphate on energy density, which hurts vehicle range and weight. Its better temperature tolerance and safety make it look more compelling for home storage, grid use, or charging buffers before it becomes common in cars.

    Do not assume every lower-cost battery chemistry is headed first into passenger EVs. For product planning, watch sodium-ion in stationary systems and cold-weather niches before treating it as a near-term default for mass-market vehicles.

      Attribution:
    • cogman10 #1
    • Manuel_D #1
    • cromka #1
    • MaKey #1
    • nine_k #1

Against the grain

  1. 01

    The hybrid motor pitch still feels hand-wavy

    A commenter who watched the Munro explainer came away unconvinced by the argument for combining motor types. The criticism was not about rare-earth-free motors themselves, but about unclear system-level justification. If the permanent-magnet machine is still used in cases where the other motor should shine, then the added complexity needs a much sharper explanation than “use the best of both.” That pushes attention back to drivetrain architecture, not just motor internals.

    If you are pitching a multi-motor or mixed-topology drivetrain, be ready to show the control strategy and operating map. Buyers and partners will want proof that the extra hardware earns its keep across real drive cycles.

      Attribution:
    • lowbloodsugar #1

In plain english

bill of materials ↩
The full list of parts and materials needed to build a product, often used as a shorthand for hardware cost structure.
EESM ↩
Electrically excited synchronous motor, a motor that creates its rotor magnetic field with electricity instead of permanent magnets.
EV ↩
Electric vehicle, a car or other vehicle powered partly or entirely by electric motors and batteries.
neodymium ↩
A rare earth element commonly used in high-strength permanent magnets for motors.
PMSM ↩
Permanent magnet synchronous motor, an electric motor that uses permanent magnets on the rotor to create its magnetic field.
power density ↩
How much power a motor or other device delivers relative to its size or weight.
slip rings ↩
Electrical contacts that transfer power to a rotating part, allowing current to reach a spinning rotor.
sodium-ion ↩
A battery chemistry that uses sodium ions instead of lithium ions to store and release energy.

Reference links

Motor explainers and teardowns

Comparable automaker implementations

Supply chain and trade policy

Battery chemistry and future powertrains