[HN Gopher] Renault: Electric motors with no rare earths
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Renault: Electric motors with no rare earths
Author : bestouff
Score : 242 points
Date : 2026-06-12 22:08 UTC (4 hours ago)
HTML web link (www.renaultgroup.com)
TEXT w3m dump (www.renaultgroup.com)
| dmitrygr wrote:
| Seems to be: replace permanent Nd magnet with an electromagnet.
| dyauspitr wrote:
| So does it consume significantly more electricity?
| cyberax wrote:
| Not really. The excitation power is a small fraction of the
| total.
|
| The problem is that it makes the rotor far less mechanically
| robust and also heavier. That's why these motors are less
| powerful.
| cyberax wrote:
| They even use regular carbon brushes to supply power to the
| magnet. Munro has a teardown video for a similar motor for
| Nissan: https://www.youtube.com/watch?v=BFmp9ODkCA8
| somat wrote:
| There is something... weird about this. this tech has
| existed.... a long time. And I am not familiar with what is
| common in electric cars so may be missing something obvious but
| thought this was already how it was done. let me explain my
| limited understanding.
|
| With ac motors electromagnets can be used in the rotor. there
| is even a super clever way to do it where the electromagnet in
| the rotor is driven wirelessly via induction. there are some
| downsides but having no physical sliding electrical connection
| to the rotor is a huge upside. The ac can be dynamically formed
| from DC via high speed switching(transistors, in industry often
| called a VFD).
|
| Due to the upsides of ac induction motors I sort of assumed
| this was already what was found in cars. I am a bit surprised
| to find out there were rare earth magnets in the first place.
| userbinator wrote:
| Permanent magnet motors are simpler and cheaper to make, at
| least in the small (yes, small --- there are electric motors
| in the MW range in industrial applications, which are
| themselves larger than an average car) sizes found in EVs.
| cyberax wrote:
| AC motors are not magic. The core is essentially just a coil
| with one turn, so it can generate only a very limited
| magnetic field. So they have to be bulkier for a given power
| density and generally slightly less efficient.
| Onavo wrote:
| The main difference between this and your typical AC induction
| motors (also magnet free) is that this is a DC motor so you need
| a commutator. Your AC induction magnet free motors are very
| similar to drone motors in that you don't have any electrically
| active moving parts like slip rings and commutators. But for AC
| induction there will be a slight lag (known as slip).
| maxerickson wrote:
| They are electronically commutated. The stator field is more or
| less variable AC.
| bgarbiak wrote:
| BMW also makes rare-earths-free motors for their EVs and - at
| this very moment - theirs are far more advanced. They offer
| almost twice the power (up to 300kW vs 160kW) and are on a 800v
| architecture.
| PedroBatista wrote:
| The cheapest EV model Renault sells is around EUR20K, the
| cheapest BMW EV is around EUR65K.
|
| It's safe to say the companies are not in the market bracket,
| no?
| alephnerd wrote:
| They share the same OEMs, and both are following the same ex-
| China automotive strategy.
|
| Renault has also been thumbing China recently for undermining
| EU manufacturing as well [0] while China has returned to
| using Wolf Warrior diplomacy against Europe [1][2][3][4]
| using the same rhetoric that the Trump admin uses.
|
| Of course, under the Xi admin China's foreign policy has
| always viewed the EU as inferior and a has-been [5] and has
| become an active participant in the Ukraine War [6][7].
|
| Europe might not be able to trust the US, but it can't trust
| China either.
|
| [0] - https://www.reuters.com/world/china/renault-ceo-asks-
| eu-enco...
|
| [1] - https://www.globaltimes.cn/page/202605/1361926.shtml
|
| [2] - https://www.chinausfocus.com/finance-economy/dear-
| brussels-d...
|
| [3] - https://www.globaltimes.cn/page/202605/1362161.shtml
|
| [4] -
| http://news.china.com.cn/2026-06/10/content_118541873.shtml
|
| [5] - https://fddi.fudan.edu.cn/_t2515/57/f8/c21257a743416/pa
| ge.ht...
|
| [6] - https://www.reuters.com/business/aerospace-
| defense/russians-...
|
| [7] - https://www.pravda.com.ua/eng/news/2026/06/12/8039041/
| nine_k wrote:
| It's still good to know that SOTA is further, and we can
| expect the more advanced designs to seep into more affordable
| segments.
| lostlogin wrote:
| The bit the gets me more than the sale price is servicing.
|
| BMWs have a terrible record for needing expensive repairs.
|
| I know you shouldn't rely on anecdote, but it seems I do.
| fnord77 wrote:
| same order of magnitude :)
| Quarrel wrote:
| Which is quite the contrast to Mercedes new axial flux electric
| motor, which goes all in on rare earths- the design relies on
| the highest end high-grade permanent magnets.
|
| Still, presumably Mercedes ambitions are for few motors than
| BMW or Renault.
| andwur wrote:
| Vastly different target market and/or features there.
| Mercedes are chasing maximum power density, minimum weight
| for high performance deployments, with seemingly little
| concern for cost or supply chain.
|
| Renault is going after the consumer market with these motors,
| where minimising cost and maximising availability is more
| important than pushing past 95% efficiency or cramming a
| 700kW power output in a motor that is small and light enough
| to fit inside of a wheel hub.
| alephnerd wrote:
| Mentioned in another HN thread [0]:
|
| They're also used by Nissan [1], BMW [2], and Indian EVs [3].
|
| European firms like ZF, Valeo, MAHLE, and Schaffler along with
| British firms like AEM have been working with their Indian JVs as
| well as Indian players like Sona Comstar and Sterling for a
| couple years now to integrate supply chains for mass-producing
| EESMs.
|
| EESMs as well as the larger OEM story played a role in helping
| land the EU-India and the UK-India FTAs because the supply chains
| for French+Italian (Renault, Stellantis), Japanese (Toyota,
| Honda, Suzuki), Korean (Hyundai-Kia), and Indian automotive
| manufacturers merged.
|
| On the other hand, EESM EVs aren't a thing here in North America
| nor China yet as both primarily use PMSMs (edited typo).
|
| [0] - https://news.ycombinator.com/item?id=48510402
|
| [1] - https://leandesign.com/nissan-ariya-magnet-free-motor-
| teardo...
|
| [2] - https://www.bmwblog.com/2025/02/20/bmw-gen6-electric-
| motors-...
|
| [3] - https://www.reuters.com/world/china/india-revs-up-
| alternate-...
|
| ---
|
| Edit: can't reply
|
| > does Nissan still use these motors, the car in the linked
| article has been discontinued
|
| Yes. The Ariya was discontinued in North America (EDIT: USA, TIL
| still sold in Canada) but is still manufactured and sold in Asia.
|
| > European and Indian manufacturers/engineering are definitely
| not in the same category though
|
| It's the same manufacturers and supply chain now.
|
| Renault and their OEMs are the biggest driver for EESM, and
| Renault's largest markets and manufacturing hubs are France,
| India, and Romania. Heck, Renault is now going to start exporting
| it's Made in India cars and parts back to the EU [0] becuase of
| the EU-India FTA.
|
| And the European OEMs have transferred the IP for EESMs to Indian
| JVs as I mentioned. It's the same style of tech transfer as
| Samsung did for BYD and TDK for CATL for battery chemistry in the
| 2000s. Heck, Valeo [1], MAHLE [2], ZF [3], and Schaffler [4] are
| opening and expanding factories and R&D hubs dedicated to EV
| transmission manufacturing in India for domestic and export
| usecases.
|
| Also, if you've ever driven a Japanese (Toyota, Honda, Suzuki) or
| Korean (Hyundai, Kia) make care in the EU, Australia, Middle
| East, Africa, or Asia outside of their home countries their parts
| sourcing and even the entire manufactured car would have come
| from India, such as the Toyota Urban Cruiser EV [5].
|
| [0] - https://m.economictimes.com/industry/auto/auto-news/india-
| eu...
|
| [1] - https://www.valeo.com/en/valeo-inaugurates-new-electric-
| powe...
|
| [2] - https://auto.economictimes.indiatimes.com/news/auto-
| technolo...
|
| [3] - https://press.zf.com/press/en/releases/release_66050.html
|
| [4] - https://www.basispointinsight.com/Story/schaeffler-india-
| ope...
|
| [5] - https://newsroom.toyota.eu/the-all-new-toyota-urban-
| cruiser/
| analogpixel wrote:
| Not sure why this was voted down, it was the most useful
| comment here.
|
| does Nissan still use these motors, the car in the linked
| article has been discontinued, and then only real info I can
| find on their site about the leaf is about their ROCKIN' bose
| sound system/s
| IlikeMadison wrote:
| Because it's grossly untrue and backed with propaganda slop
| articles. I suspect this is a bot.
| AtlasBarfed wrote:
| what is a prsm? Do you mean pmsm?
| IlikeMadison wrote:
| European and Indian manufacturers/engineering are definitely
| not in the same category though.
| heresie-dabord wrote:
| > The Ariya was discontinued in North America but is still
| manufactured and sold in Asia.
|
| The Nissan Ariya is NOT discontinued in North America. Nissan
| no longer sells it in the USA because of Trump's tariff war.
|
| The Nissan Ariya is still sold in Canada.
| IlikeMadison wrote:
| No, and it was mentioned by the consortium of European cars
| manufacturers after the joint press release with Der Leyen
| herself: the implementation of factories and research centers
| in India is solely to be able to sell on that market. It is the
| exact same process that happened with China in the past. The
| exact same also happened with Airbus.
|
| You are also wrong on the market importance for Renault. For
| 2024, France was the biggest, followed by Italy, Turkey, Spain,
| Germany, Brazil, UK, Morocco, BENELUX, Romania, Poland,
| Netherlands and... #13 India with 0.9% market share...
|
| Supply chains didn't change at all, in fact it did the
| opposite, and Europeans won't rely on anything Indian made for
| the near future, as local re-industrialization is already acted
| on and even accelerated since the pandemic.
|
| Production numbers across all manufacturers even Volkswagen
| (which was unexpected) show the number of cars manufactured in
| Europe increased in the past 2 years.
|
| Electric cars in Europe mostly come from China, the US and
| European brands. Nothing Indian-made, not even parts.
| delfugal wrote:
| How soon to see rare-earth-free paired with CATL Sodium
| batteries? Seems a price war, range war is imminent.
| alephnerd wrote:
| Unlikely.
|
| EESMs are primarily manufactured by European OEMs (ZF, MAHLE,
| Schaffler, AEM) and their Indian JV partners (Sona Comstar,
| Sterling, and the India branches of the OEMs listed). Both have
| been blocked via export controls from accessing battery tech
| from China over the past few years, and a major reason for the
| push for EESMs was for an ex-China supply chain, especially
| after China began export controlling rare earths to the EU [6].
|
| Additonally, Chinese and American EVs tend to use PMSMs unlike
| European and now Indian EVs. Also, the EU is cracking down on
| automotive exports (cars and OEMs) from non-FTA states as part
| of the EU Industrial Accelerator Act (which btw has made China
| go ballistic [2][3][4][5]).
|
| On the other hand, they will most likely use Japanese or Korean
| solid-state batteries as Idemetsu Kosan is in the process of
| mass producing them [0][1] as is LG [7], and both Japan+SK are
| FTA partners with the EU.
|
| [0] -
| https://www.chiyodacorp.com/en/projects/solidelectrolytefaci...
|
| [1] - https://battery-tech.net/battery-markets-news/idemitsu-
| kosan...
|
| [2] - https://www.globaltimes.cn/page/202605/1361926.shtml
|
| [3] - https://www.globaltimes.cn/page/202605/1362200.shtml
|
| [4] - https://www.globaltimes.cn/page/202605/1362161.shtml
|
| [5] -
| https://www.ft.com/content/5903318c-319b-426e-b05d-062f7620f...
|
| [6] - https://www.reuters.com/world/china/eu-lawmakers-rebuke-
| chin...
|
| [7] -
| https://blog.lgchem.com/en/2026/03/25_solid_state_battery/
| cogman10 wrote:
| Could be wrong, but AFAIK the CATL Sodium batteries haven't yet
| hit LFP pricing.
|
| You are unlikely to see a vehicle with sodium batteries until
| after that happens, and it needs to be significantly less than
| LFPs as you Na batteries have more weight per Wh. I believe
| they also have a shorter lifespan (but not NMC short). _Edit_
| correction, looks like CATL is promising 15000 cycles, which is
| much longer than LFPs which usually come in at 7000 to 10000.
|
| It seems far more likely to me that if the Na prices tank,
| you'll probably first see them deployed as grid and home
| battery solutions.
| MaKey wrote:
| One of the most interesting features of sodium batteries is
| that they still perform good in cold temperatures.
| cromka wrote:
| And high temperatures, too. Meaning they don't require
| cooling nor heating, basically matching the per kg capacity
| of ready modules with LFP while being significantly safer
| and less complex.
| nine_k wrote:
| Looks ideal for a power wall at home.
| AtlasBarfed wrote:
| Superior temperature range in cold weather as well IIRC.
| Manuel_D wrote:
| The energy density of LFP batteries are also 30-50% higher
| than sodium based battery chemistries. Even if sodium battery
| prices drop, the lower energy density is a big disadvantage.
| My understanding is that sodium batteries are aimed at
| stationary use-cases, like battery buffers for fast charging.
| gpm wrote:
| They're promising to start selling a Qiyuan A06 variant with
| Sodium batteries sometime this year... so if you went looking
| you could probably see one... or will be able to soon.
| willXare wrote:
| "Replace the magnet with a controllable magnet" is probably the
| most automotive-engineering sentence possible.
| pfannl wrote:
| Also known as: "we removed the rare earths and added software."
| Jblx2 wrote:
| Synchronous motors: running on software since the 1880s.
| Nikola really was ahead of his time!
| hnav wrote:
| He invented the induction motor which runs right off the
| grid.
| derac wrote:
| https://youtu.be/FHufjrP0xDI?is=xmFQrXGa1dBHM67I
|
| This is a helpful explanation of what this technology is and
| looks like. (Munro)
| lowbloodsugar wrote:
| It was a dude with motors on a table with a flip board. No
| animations. No diagrams. When it got to the point about having
| one of each motor, and using the best, he then said that you
| use the permanent motor even when the other makes sense. Ok,
| well then why have the two different kinds of motors? No
| answer. Just handwaved. If you can't use the induction motor
| when its most efficient, because thats when the permanent motor
| is causing spin loss, why have the induction motor at all? No
| answer.
|
| So. Analog presentation. Actual motors on a desk with a flip
| chart. No animations. No internal visualizations. One page had
| diagrams that would have been better super-imposed (or hey,
| animated). Then one page the begs questions with no answers
| given.
| hijinks wrote:
| let me guess.. but its 2x the price?
| hnav wrote:
| no, but requires introduces brushes (slip-rings really) which
| is a wear item
| themafia wrote:
| Cars already have lots of wear items and a mature service
| industry for them. If I can reliably get at least 50k miles
| out of it, then I wouldn't be all that bothered, as this is
| not likely to be an expensive part or service.
| drnick1 wrote:
| > mature service industry for them
|
| The car service industry is a scam, and I am glad that EVs
| require minimal to no servicing that cannot be easily DIY
| like tires and brakes.
| hnav wrote:
| so apparently on the BMW i4s it requires a rear subframe
| drop which isn't going to be cheap (10s of hours).
| giobox wrote:
| It's interesting that this is a brushed design. In the RC car
| community, brushless motors are generally regarded as superior,
| but those of course have the rare earth magnet problem.
|
| Technically the brushes can wear out, although there are claims
| they are good for 150,000-250,000 miles it seems.
| hnav wrote:
| It's technically not a brush but a slip-ring. The design of
| these motors is very similar to automotive alternators, just
| scaled up 100x (in terms of power).
| dheera wrote:
| Slip rings have brushes.
| raverbashing wrote:
| Yes but they wear less than DC brushed motors exactly
| because it's a slip ring and not a commutator
| ahartmetz wrote:
| Because it's the discontinuities in the commutator where
| the sparks fly (with much help from self-induction of the
| motor's coils) and erode the ring and brushes.
| genter wrote:
| I've probably taken apart 10 automotive alternators. Every
| single one had brushes.
| hnav wrote:
| yeah I misspoke, I meant to say that it's a brush riding on
| a slip-ring (continuous contact, no arcing, lasts long)
| rather than a bunch of contacts in a cylinder (commutator,
| arcing, wears out).
| ipbrown wrote:
| Electrically excited synchronous machines (EESMs), also known as
| wound field synchronous machines (WFSMs) have a number of
| potential advantages and disadvantages compared to interior
| permanent magnet synchronous machines (IPMSMs). IPMSMs are the
| dominant motor topology currently in use for North American
| electric vehicles.
|
| Advantages:
|
| - Not subject to the price and supply chain volatility of rare
| earth permanent magnets.
|
| - For highway dominant drive cycles, the cycle efficiency of
| EESMs can be higher than state of the art IPMSMs. EESMs tend to
| have their best efficiency at moderate torques and high speeds
| because of their excellent field weakening characteristics. I
| tend to think that they would be a good fit for application in
| class 8 trucks or as auxiliary motors in automobiles with two
| powered axles.
|
| - The output torque doesn't necessarily decrease with rotor
| temperature. In IPMSMs the permanent magnet flux linkage
| decreases with rotor temperature.
|
| - At least theoretically, with proper control, it is possible to
| operate EESMs with unity power factor and decrease the kVA rating
| of the stator inverter.
|
| - If there is a stator inverter fault, there are schemes to
| denergize the rotor which have some safety implications.
|
| Disadvantages:
|
| - DC current needs to be transferred to the rotating field
| winding. For automotive applications this tends to be done either
| with brushes and slip rings or brushlessly using a high frequency
| transformer with a rotating rectifier. In either case additional
| power electronics and other components are needed for the field
| power transfer and control which reduces some of the potential
| cost savings of the elimination of the permanent magnets. If
| brushes and slip rings are used with oil spray/oil jet cooling of
| the rotor they need to be sealed in a separate compartment. I am
| a little surprised that Renault has stuck with brushes and slip
| rings versus an inductive high frequency transformer solution. I
| think this has limited their power density.
|
| - For very torque dense machines, cooling the rotor field winding
| is challenging, and in my opinion is best accomplished by oil
| spray/oil jet cooling.
|
| - It is difficult to reach the same maximum speeds as IPMSMs in
| an automotive package size. The rotor field winding retention
| system to keep the field turns from moving into the airgap at
| high speeds needs considerable attention during the design.
|
| - The overall axial length of the non-active region of EESMs is
| typically longer than IPMSMs because of the field winding end
| turns and field excitation system.
|
| - EESM efficiency is dominated by the manufacturable slot fill of
| the field winding.
|
| - High performance current/torque regulation is considerably more
| difficult.
|
| High performance EESMs have been used in aerospace generator
| applications for decades, albeit with a different rotor
| excitation system than what is used in automotive applications.
| Renault (and their supplier Continental) really led the
| commercialization of EESMs into automotive mass production. Now
| BMW has followed suit and multiple suppliers have EESM designs
| (Mahle, ZF, etc.) GM had a really nice EESM design and high
| frequency transformer excitation which they published back in
| 2014. My colleagues and I built several generations of EESMs as
| part of U.S. Dept. of Energy projects
| (https://www.osti.gov/servlets/purl/1837809) and I think they
| have their place as EV traction motors for certain applications.
| userbinator wrote:
| _A historical pioneer in the complex technology of electric
| motors without magnets_
|
| Those who know the history of electric machines will find the
| title and verbiage very amusing. Motors with no permanent magnets
| were the first practical ones, and at this point wound-rotor
| motors are over a century old.
|
| It's worth noting that some of the biggest motors have always
| been designed this way, because the size of magnets required
| would make them both too expensive and dangerous, and still not
| powerful enough for their size; a field coil can generate a field
| that's only limited by the current and resistive heating of the
| winding, but rare earth magnets have fixed limits on field
| strength.
| XorNot wrote:
| Not quite true: you're also limited by the mechanical strength
| of your windings and core (this is the upper limit on
| superconducting magnets like at CERN and in fusion plants).
| Jblx2 wrote:
| And if you also ignore iron saturation.
| xeonmc wrote:
| What advantage do permanent magnets provide that it isn't the
| case that all motors are made without them?
| sitharus wrote:
| A lack of wear components.
|
| A permanent magnet motor uses permanent magnets on the rotor,
| but an electrically excited synchronous motor has an
| electromagnet on the rotor. This requires a rotating
| electrical contact which has normally been made with slip
| rings and carbon brushes. These wear over time and need
| replacement.
|
| Most large electric generators are externally excited
| synchronous generators using carbon slip rings, so it's a
| well understood field.
|
| This can be made contactless using inductive coupling and a
| rectifier - since inductive coupling needs AC but the
| excitation coil needs DC - at the expense of some efficiency.
|
| You can see the efficiency difference - Renault claim 92%
| efficiency but permanent magnet motor EVs have touted
| efficiency over 95% in the motor.
| Rapzid wrote:
| To a layman that seems like a really small efficiency tax
| if you can't get your hands on the magnets for some reason.
| handstitched wrote:
| It's a small difference, but if you had a choice between
| "more efficient AND less maintenance" and "less efficient
| and more maintenance" then it's easy to see why the
| permanent-magnet solution is preferred.
| isopede wrote:
| Does regenerative braking work with a motor like this?
| ahartmetz wrote:
| After watching a Munro video about it, I see your point. In the
| motor shown, the rotor gets its magnetic field simply by
| inducing a current and a field in it in reaction to the
| stator's field. There are no electromagnets in the rotor like I
| expected. In that case, I'm not sure either... I'd say more
| likely than not but it's complicated since the stator basically
| needs to induce a field and at the same time recover energy
| from the field that comes back from the rotor. I would further
| guess that the phase shift between the two components makes it
| possible to treat them separately.
|
| Previous comment: Don't see why not - the "field" coils (the
| ones that replace the permanent magnets) need to be energized,
| which can initially come from the batteries if necessary.
| maxerickson wrote:
| There are electromagnets in the rotor, it is directly
| energized.
| cwillu wrote:
| Yes: IIRC some large generators work exactly like this, as the
| energized rotor gives a lot more flexibility in managing
| frequency and power output.
| fc417fc802 wrote:
| Not just some, approximately all of them. It greatly
| complicates the logistics of a black start. + Of course that
| situation has additional complexity due to the need for
| substantial additional power in order for the various fuel
| supply systems to operate but I digress.
|
| + https://en.wikipedia.org/wiki/Black_start
| MrDrMcCoy wrote:
| It's a bummer they are not really available in the US.
| alephnerd wrote:
| EVs in the US and China tend to use PMSMs, though GM,
| Stellantis, the DoE, and the DoD are funding an EESM startup
| [0]
|
| [0] - https://nironmagnetics.com/
| numpad0 wrote:
| Weren't Tesla ACIM drive unit motors before Model 3 also magnet-
| free? I thought they used passive isolated bundles of copper
| wires and their reluctance as magnets.
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