6 ms·

No Magnets, Big Power: BMW’s Fifth-Generation Electric Motor (2022)

76 points by clouddrover 4y ago

wwalexander 4y ago
Has BMW stopped using plastic parts everywhere? Nothing environmentally friendly about a disposable engine in a luxury car.
- ravenstine 4y ago
  Why couldn't plastic be recycled for this purpose? Engine components seems like a perfect application for recycled plastic, whereas it can be challenging when it comes to food grade packaging, etc. There's nothing particularly environmentally friendly about vehicle production in general, so it kinda seems to me that this point is grasping at straws.
  - slackdog 4y ago
    > Engine components seems like a perfect application for recycled plastic, I would expect the opposite, at least for any component which might get hot when the engine itself is hot, because thermoplastics soften when heated. Thermoset plastics don't soften, but as a general rule thermoset plastics aren't recyclable.
  - wwalexander 4y ago
    The issue isn’t recycling the plastic, the issue is an entire vehicle going to the junkyard when the planned-obsolescence plastic engine parts inevitably fail.
- hyperbovine 4y ago
  Plastic is not environmentally unfriendly. Tossing plastic into the ocean is environmentally unfriendly.
  - JeanMarcS 4y ago
    I have no expertise in that field, so perhaps I'm gonna say something wrong, but isn't plastic comming from oil ? Extraction, transport, refining... That doesn't sound environmentally friendly to me.
    - the_pwner224 4y ago
      What else would you use? Metal? That's not a whole lot better for the environment. "Natural" materials like wood, glass, rubber are not a suitable replacement for many uses of plastic, or would require changes that would overall make it worse. We could make car bumpers out of wood instead of plastic. Then you'd have heavier cars which use more fuel and are less safe (and more expensive). The amount of waste generated by these uses of plastic is negligible and well worth it when you compare to the alternatives. There are many, many bigger sources of plastic usage & waste which we should tackle first before we focus on durable non-disposable plastics.
    - hyperbovine 4y ago
      For a long time I looked at it this way. But let’s be honest with ourselves: plastic is not going anywhere. It’s too useful and too integrated into the global economy. Oil extraction is energy intensive and environmentally harmful, but so are many other industrial processes. As long as the carbon it contains does not end up on the atmosphere or ocean, I don’t see why we should view plastic differently than aluminum, steel, cement, or ammonia.
  - wwalexander 4y ago
    And tossing entire vehicles into the junkyard when the plastic engine inevitably decays and fails is VERY environmentally unfriendly.
- deleted 4y ago
  [deleted]
- pleb_nz 4y ago
  What give you the impression these are disposable motors?
  - wwalexander 4y ago
    https://jalopnik.com/bmw-engines-are-gigantic-pieces-of-shit-1784684330 https://jalopnik.com/bmw-engines-are-gigantic-pieces-of-shit...
    - pleb_nz 4y ago
      While I don't doubt this person's experiences, I've never have a BMW so can't comment. But this has nothing to do with the new motor being designed to be disposable and it seems to mention the brushes are serviceable...
canbus 4y ago
>It's clear that the battle for magnet-less motor supremacy is only just getting started, and BMW is answering a key criticism frequently leveled against EVs: relying on rare, sometimes unethically mined materials makes EVs worse for the planet. We're truly stepping into an interesting time in electric motor development. Right, what about the huge lithium batteries though? they're not exactly ethically sourced either...
- bryanlarsen 4y ago
  Cobalt-free lithium batteries are expected to be the most common EV battery in the near future. LiFePO4 batteries are already the most common EV battery in China. For high future performance applications, Tesla's high nickel chemistry doesn't use cobalt.
  - rootusrootus 4y ago
    > LiFePO4 batteries are already the most common EV battery in China Pretty common in the US as well, in terms of total EVs sold. I wonder if we will see almost all regular EVs switching over to LFP by the end of this decade.
londons_explore 4y ago
Magnetless motors lag behind magnet-ed motors for efficiency. However you design it, a magnet creates a magnetic field with zero power use, whereas any other source of magnetic field generation ends up using electrical power, generating heat (in a part hard to cool), and usually heavier for the same torque. I'm disappointed that BMW doesn't give efficiency figures in their press release, because that is what has been pushing everyone else to the various kinds of BLDC/SynRM machines.
- deleted 4y ago
  [deleted]
- 34679 4y ago
  The article claims the opposite. I haven't looked at BMW's press release, so I don't know where the claim comes from. "It's a big advance in terms of the efficiency of the electric motor, while getting away from the use of rare earth minerals." Their reasoning: "Permanent magnet machines typically rank as the most power-dense electric motors, but there's no turning permanent magnets "off." Their magnetic fields never change, so when they're not being powered by energy in the stator winding, they're generating energy in those windings, which creates drag."
  - zwieback 4y ago
    Yeah, but only by adding a clutch or something to prevent the drag when the motor is coasting. I'm a little confused by this, I thought the motor would turn into a generator in that situation.
    - londons_explore 4y ago
      It would be theoretically possible to have a magnetic 'switch' which turned the permanent magnets off when not needed. Sounds impossible but it's possible[1]. [1]: https://www.goudsmitmagnets.com/en/solutions/magnetic-handling/switchable-welding-magnets https://www.goudsmitmagnets.com/en/solutions/magnetic-handli...
tromp 4y ago
These brushed motors generate fine dust like a brake pad in very slight but constant use: > We asked BMW about the life expectancy of those brushes and commutators, and what happens to the dust as they wear. While they couldn't give us a lifetime estimate for the brushes, they did reassure us that the brush modules are "in an enclosed and sealed compartment, eliminating dust contamination inside the stator/rotor wiring." Anyone who has worked with brakes or even brushed DC motors knows just how fine those dust particles are. It will be interesting to see both how long they last and just how much dust those modules will actually contain (or release).
- throwaway4PP 4y ago
  Interesting. I cynically view this (brushed motors with reduced lifetime as compared to brushless, sold as a benefit b/c free of rare earth) as just another self-serving decision automakers can make in the push to reduce the usable lifetime of EVs. The longevity of ICE/hybrid vehicles has long been a bugbear for auto manufacturers. One of the convenient things for them in the push for EVs is that EVs will inherently have less utility at 10 - 15 years than ICE vehicles. With manufacturers' standard EV warranty including 70% bat capacity at 10 years or XYZ miles, it's almost like an ICE manufacturer saying your gas tank will get 30% smaller after a decade. Except that an aging battery also has reduced current draw and thermal allowances, so there is also less instantaneous power available as the battery pack ages. This is an engineering reality of battery EVs, to keep them safe as their packs age. The power limit could be viewed as consistent with older ICE's not performing at nameplate HP, which none of them will without significant maintenance. But this is why I'm cynical about automakers and EVs: EVs lower their cost burden in the medium to long term with simplified production, and "enhanced" planned obsolence via wear components that are much more expensive and can significantly limit the utility of the vehicle in the 10 - 20 year time horizon, as compared to ICEs and maybe hybrids.
  - the_pwner224 4y ago
    This doesn't pass the smell test. They can already do that - they arguably are already doing that (*) - by making combustion engines which aren't reliable in the long term. And there are so many other things that you can design to be unreliable in the long term, especially in modern cars which have lots of features. They're warrantied at 70% for 10 years because that's what the law requires. It doesn't mean you're going to lose 30% over 10 years. We could also see manufacturers put a better warranty on their vehicles as a selling point. I haven't done much research into this, but I believe the existing EVs from various manufacturers have had very good battery degradation characteristics over time and over mileage. Not anything remotely like 70% over 10 years. If you look at technical documents and presentations that manufacturers create for industry trade shows, training their technicians, and in press releases for new models, they seem to genuinely care about battery degradation and mention all the things they're doing to ensure a long battery life. Obviously the situation might change in the future and companies may decide to become greedy, but for now this doesn't appear to be an issue. And as battery technology (& capacity) advances over time, this is going to be less of a problem in the future. (*) Edit: That was poorly worded. I'm not saying it's common practice to intentionally design things to break, but that manufacturers who get greedy and cut costs are naturally going to end up making drivetrains that don't last 10+ years. Nissan's CVT debacle is a perfect example. The companies who would skimp on spending $$$ for battery management are already doing the same things right now with their ICE products. But what we've seen as an industry trend is that manufacturers for the most part don't intentionally sabotage their products; in fact cars have been slowly but steadily getting more reliable over time. Going from ICEs to EVs doesn't change this situation at all. Another example is anti-corrosion coatings on the frame and underbody. They could easily save $$$ here with no noticeable effect to the customer until 10 years down the line. But across the industry, we see that luxury brands choose to spend extra $ on advanced coatings (when they could use the cheaper value coatings which the economy brands use), and the economy brands have also been upgrading to the newer coatings as cost comes down (rather than sticking with the older cheaper coatings). Just like how engines have become more reliable over time, the frames of modern cars last much longer than older cars. The industry in general is not sabotaging their products, they are genuinely trying to make good quality products.
boringg 4y ago
Is one of the big advantages of these no magnet motors that they have a reduced need on rare earth metals? I thought this was a big advantage for Tesla's announcement recently - which has implications for relying on foreign miners / allows for cost reductions over time as supplies decrease. Can someone confirm my understanding - thanks!
- Tade0 4y ago
  You can achieve the same type of independence with AC induction motors - that's even what early Teslas used. Overall efficiency is worse though. There's a lot going on lately in the magnet/motor space - all to wean us off rare earths.
  - boringg 4y ago
    Got it - so my original supposition is correct that were really trying to reduce (A) dependence on rare earths which will (B) give us more direct control on pricing in the long run. The trade off with that is that we have a lower overall efficiency of use.
frankus 4y ago
I’m pretty sure they’re describing a wound-rotor synchronous motor. In that case it wouldn’t have a commutator per se but constant-contact slip rings. These last a lot longer since they’re not subject to arcing. The advantage is that unlike with permanent magnets it’s possible to reduce the strength of the rotor’s magnetic field at will (although there are some hacks that can be done with field-oriented control that provide the same field-weakening effect).
- HPsquared 4y ago
  The automotive industry is already familiar with slip rings, used for decades in alternators. I wonder if the supplier of this motor also makes alternators...
- danbruc 4y ago
  Is there even a need for commutators, could you not always use slip rings and electronically commutate within the rotor?
  - frankus 4y ago
    Once you have electronic commutation it usually makes sense to just make the magnetic field rotate in the stator and keep it fixed in the rotor. That way you avoid putting hot electronics in an already difficult-to-cool area that may also need to withstand some serious g forces. But you do need some way to magnetize the rotor (setting aside reluctance motors) so that probably means permanent magnets, an induction-powered electromagnet, or a conduction-powered electromagnet (via slip rings). Old-school DC motors use commutators in times and places where electronic commutation is too expensive or hadn’t been invented yet. I’m not aware of any configurations where the commutator creates a field that rotates relative to the stator, probably because you’d need to send the power into and back out of the rotor so there are twice as many parts to wear out.
hristov 4y ago
Using brushed motors in 2023 is really stupid. Yes I know there is a semiconductor shortage, I know Silicon Carbide is expensive and silicon is not very efficient. But seriously. Batteries are also expensive. And brushed motors are very inefficient. This is just another sign that BMW is way behind in electrification.
nerpderp82 4y ago
I think this might validate Neil Saiki's (no longer with the company) view on brushed motors for their electric motorcycles (Zero Motorcycles). https://www.youtube.com/watch?v=0hQ7S3QPSpI https://www.youtube.com/watch?v=0hQ7S3QPSpI They later moved to brushed motors, but I believe that was more for customer demand and not a direct engineering reason. Who knows of the exact solution for brush lifetime in the BMW motor, but one could absolutely have a sweeper, a reservoir and brushes that could last 1M miles or more. Maybe the solution is to have brushes in a cartridge that could be replaced. Only an engineering problem. If the major ingredient into your system is iron, your asymptotic cost is lower than $1/lb. I really appreciate Neil's engineering ascetic, it seems brutally honest.
sandworm101 4y ago
I wonder how much of this is due to legal issues. By switching to brushless, do they avoid and of the recent patents re the brushless motors that have dominated EVs?
DakotaR 4y ago
That's really interesting that they picked brushes; Renault's EESM motors are similar but use wireless power transfer to excite the rotor windings. Maybe brushes can pass more current cheaply?
- creeble 4y ago
  Yes, brushless necessitates more rotating mass plus the loss in the wireless exciter. Longer life (no brush changes or slip ring wear), but lower efficiency. I wonder if a hybrid rotor would pay off? It would still need brushes, but the current could be less to make them last longer. Probably a problem with demagnetizing the fixed magnets or something.
752963e64 4y ago
[dead]
seanhunter 4y ago
BMW are very good at innovations using old/unfashionable tech and are happy to sometimes be a bit eccentric/different from everyone else. I have a BMW motorcycle with a "Boxer"[1] engine which is the product of a process of continuous refinement of an original 1923 design. It's an amazing engine design that is almost completely unknown outside of BMW. On the other hand, my old BMW motorcycles had a design for the indicator controls that everyone in the industry found really weird and ended up being abandoned[2] [1] Horizontally opposed twin cylinder https://www.carolenash.com/news/bike-news/detail/a-brief-history-of-bmws-boxer-engine https://www.carolenash.com/news/bike-news/detail/a-brief-his... [2] I actually liked the old design but w/e
- deleted 4y ago
  [deleted]
WirelessGigabit 4y ago
Replacing the brushes as they wear out: fine. But what about the dust accumulating inside and sticking everywhere, adding additional wear. I guess we'll see how many iXs are still on the road in 5 years.
- darksaints 4y ago
  It uses slip rings like your alternator, not a commutator like a typical brushed DC motor. I’ve had alternators that have lasted more than 20 years, and they don’t have dust problems. There’s no arcing and there is a continuous contact surface, so there isn’t really any dust.
rajnathani 4y ago
> ..there's no turning permanent magnets "off. " Their magnetic fields never change, so when they're not being powered by energy in the stator winding, they're generating energy in those windings, which creates drag. This is why some EVs powered by multiple motors either use a clutch to decouple and idle a permanent-magnet motor when it's not needed, or they fit one asynchronous AC induction motor (which suffers no such losses) and one permanent-magnet motor. This part is really interesting from a physics energy (thermodynamics?) standpoint.

76 points by clouddrover 4y ago

Has BMW stopped using plastic parts everywhere? Nothing environmentally friendly about a disposable engine in a luxury car.

ravenstine 4y ago
Why couldn't plastic be recycled for this purpose? Engine components seems like a perfect application for recycled plastic, whereas it can be challenging when it comes to food grade packaging, etc. There's nothing particularly environmentally friendly about vehicle production in general, so it kinda seems to me that this point is grasping at straws.
- slackdog 4y ago
  > Engine components seems like a perfect application for recycled plastic, I would expect the opposite, at least for any component which might get hot when the engine itself is hot, because thermoplastics soften when heated. Thermoset plastics don't soften, but as a general rule thermoset plastics aren't recyclable.
- wwalexander 4y ago
  The issue isn’t recycling the plastic, the issue is an entire vehicle going to the junkyard when the planned-obsolescence plastic engine parts inevitably fail.
hyperbovine 4y ago
Plastic is not environmentally unfriendly. Tossing plastic into the ocean is environmentally unfriendly.
- JeanMarcS 4y ago
  I have no expertise in that field, so perhaps I'm gonna say something wrong, but isn't plastic comming from oil ? Extraction, transport, refining... That doesn't sound environmentally friendly to me.
  - the_pwner224 4y ago
    What else would you use? Metal? That's not a whole lot better for the environment. "Natural" materials like wood, glass, rubber are not a suitable replacement for many uses of plastic, or would require changes that would overall make it worse. We could make car bumpers out of wood instead of plastic. Then you'd have heavier cars which use more fuel and are less safe (and more expensive). The amount of waste generated by these uses of plastic is negligible and well worth it when you compare to the alternatives. There are many, many bigger sources of plastic usage & waste which we should tackle first before we focus on durable non-disposable plastics.
  - hyperbovine 4y ago
    For a long time I looked at it this way. But let’s be honest with ourselves: plastic is not going anywhere. It’s too useful and too integrated into the global economy. Oil extraction is energy intensive and environmentally harmful, but so are many other industrial processes. As long as the carbon it contains does not end up on the atmosphere or ocean, I don’t see why we should view plastic differently than aluminum, steel, cement, or ammonia.
- wwalexander 4y ago
  And tossing entire vehicles into the junkyard when the plastic engine inevitably decays and fails is VERY environmentally unfriendly.
deleted 4y ago
[deleted]
pleb_nz 4y ago
What give you the impression these are disposable motors?
- wwalexander 4y ago
  https://jalopnik.com/bmw-engines-are-gigantic-pieces-of-shit-1784684330 https://jalopnik.com/bmw-engines-are-gigantic-pieces-of-shit...
  - pleb_nz 4y ago
    While I don't doubt this person's experiences, I've never have a BMW so can't comment. But this has nothing to do with the new motor being designed to be disposable and it seems to mention the brushes are serviceable...

canbus 4y ago

>It's clear that the battle for magnet-less motor supremacy is only just getting started, and BMW is answering a key criticism frequently leveled against EVs: relying on rare, sometimes unethically mined materials makes EVs worse for the planet. We're truly stepping into an interesting time in electric motor development. Right, what about the huge lithium batteries though? they're not exactly ethically sourced either...

bryanlarsen 4y ago
Cobalt-free lithium batteries are expected to be the most common EV battery in the near future. LiFePO4 batteries are already the most common EV battery in China. For high future performance applications, Tesla's high nickel chemistry doesn't use cobalt.
- rootusrootus 4y ago
  > LiFePO4 batteries are already the most common EV battery in China Pretty common in the US as well, in terms of total EVs sold. I wonder if we will see almost all regular EVs switching over to LFP by the end of this decade.

londons_explore 4y ago

Magnetless motors lag behind magnet-ed motors for efficiency. However you design it, a magnet creates a magnetic field with zero power use, whereas any other source of magnetic field generation ends up using electrical power, generating heat (in a part hard to cool), and usually heavier for the same torque. I'm disappointed that BMW doesn't give efficiency figures in their press release, because that is what has been pushing everyone else to the various kinds of BLDC/SynRM machines.

deleted 4y ago
[deleted]
34679 4y ago
The article claims the opposite. I haven't looked at BMW's press release, so I don't know where the claim comes from. "It's a big advance in terms of the efficiency of the electric motor, while getting away from the use of rare earth minerals." Their reasoning: "Permanent magnet machines typically rank as the most power-dense electric motors, but there's no turning permanent magnets "off." Their magnetic fields never change, so when they're not being powered by energy in the stator winding, they're generating energy in those windings, which creates drag."
- zwieback 4y ago
  Yeah, but only by adding a clutch or something to prevent the drag when the motor is coasting. I'm a little confused by this, I thought the motor would turn into a generator in that situation.
  - londons_explore 4y ago
    It would be theoretically possible to have a magnetic 'switch' which turned the permanent magnets off when not needed. Sounds impossible but it's possible[1]. [1]: https://www.goudsmitmagnets.com/en/solutions/magnetic-handling/switchable-welding-magnets https://www.goudsmitmagnets.com/en/solutions/magnetic-handli...

tromp 4y ago

These brushed motors generate fine dust like a brake pad in very slight but constant use: > We asked BMW about the life expectancy of those brushes and commutators, and what happens to the dust as they wear. While they couldn't give us a lifetime estimate for the brushes, they did reassure us that the brush modules are "in an enclosed and sealed compartment, eliminating dust contamination inside the stator/rotor wiring." Anyone who has worked with brakes or even brushed DC motors knows just how fine those dust particles are. It will be interesting to see both how long they last and just how much dust those modules will actually contain (or release).

throwaway4PP 4y ago
Interesting. I cynically view this (brushed motors with reduced lifetime as compared to brushless, sold as a benefit b/c free of rare earth) as just another self-serving decision automakers can make in the push to reduce the usable lifetime of EVs. The longevity of ICE/hybrid vehicles has long been a bugbear for auto manufacturers. One of the convenient things for them in the push for EVs is that EVs will inherently have less utility at 10 - 15 years than ICE vehicles. With manufacturers' standard EV warranty including 70% bat capacity at 10 years or XYZ miles, it's almost like an ICE manufacturer saying your gas tank will get 30% smaller after a decade. Except that an aging battery also has reduced current draw and thermal allowances, so there is also less instantaneous power available as the battery pack ages. This is an engineering reality of battery EVs, to keep them safe as their packs age. The power limit could be viewed as consistent with older ICE's not performing at nameplate HP, which none of them will without significant maintenance. But this is why I'm cynical about automakers and EVs: EVs lower their cost burden in the medium to long term with simplified production, and "enhanced" planned obsolence via wear components that are much more expensive and can significantly limit the utility of the vehicle in the 10 - 20 year time horizon, as compared to ICEs and maybe hybrids.
- the_pwner224 4y ago
  This doesn't pass the smell test. They can already do that - they arguably are already doing that (*) - by making combustion engines which aren't reliable in the long term. And there are so many other things that you can design to be unreliable in the long term, especially in modern cars which have lots of features. They're warrantied at 70% for 10 years because that's what the law requires. It doesn't mean you're going to lose 30% over 10 years. We could also see manufacturers put a better warranty on their vehicles as a selling point. I haven't done much research into this, but I believe the existing EVs from various manufacturers have had very good battery degradation characteristics over time and over mileage. Not anything remotely like 70% over 10 years. If you look at technical documents and presentations that manufacturers create for industry trade shows, training their technicians, and in press releases for new models, they seem to genuinely care about battery degradation and mention all the things they're doing to ensure a long battery life. Obviously the situation might change in the future and companies may decide to become greedy, but for now this doesn't appear to be an issue. And as battery technology (& capacity) advances over time, this is going to be less of a problem in the future. (*) Edit: That was poorly worded. I'm not saying it's common practice to intentionally design things to break, but that manufacturers who get greedy and cut costs are naturally going to end up making drivetrains that don't last 10+ years. Nissan's CVT debacle is a perfect example. The companies who would skimp on spending $$$ for battery management are already doing the same things right now with their ICE products. But what we've seen as an industry trend is that manufacturers for the most part don't intentionally sabotage their products; in fact cars have been slowly but steadily getting more reliable over time. Going from ICEs to EVs doesn't change this situation at all. Another example is anti-corrosion coatings on the frame and underbody. They could easily save $$$ here with no noticeable effect to the customer until 10 years down the line. But across the industry, we see that luxury brands choose to spend extra $ on advanced coatings (when they could use the cheaper value coatings which the economy brands use), and the economy brands have also been upgrading to the newer coatings as cost comes down (rather than sticking with the older cheaper coatings). Just like how engines have become more reliable over time, the frames of modern cars last much longer than older cars. The industry in general is not sabotaging their products, they are genuinely trying to make good quality products.

boringg 4y ago

Is one of the big advantages of these no magnet motors that they have a reduced need on rare earth metals? I thought this was a big advantage for Tesla's announcement recently - which has implications for relying on foreign miners / allows for cost reductions over time as supplies decrease. Can someone confirm my understanding - thanks!

Tade0 4y ago
You can achieve the same type of independence with AC induction motors - that's even what early Teslas used. Overall efficiency is worse though. There's a lot going on lately in the magnet/motor space - all to wean us off rare earths.
- boringg 4y ago
  Got it - so my original supposition is correct that were really trying to reduce (A) dependence on rare earths which will (B) give us more direct control on pricing in the long run. The trade off with that is that we have a lower overall efficiency of use.

frankus 4y ago

I’m pretty sure they’re describing a wound-rotor synchronous motor. In that case it wouldn’t have a commutator per se but constant-contact slip rings. These last a lot longer since they’re not subject to arcing. The advantage is that unlike with permanent magnets it’s possible to reduce the strength of the rotor’s magnetic field at will (although there are some hacks that can be done with field-oriented control that provide the same field-weakening effect).

HPsquared 4y ago
The automotive industry is already familiar with slip rings, used for decades in alternators. I wonder if the supplier of this motor also makes alternators...
danbruc 4y ago
Is there even a need for commutators, could you not always use slip rings and electronically commutate within the rotor?
- frankus 4y ago
  Once you have electronic commutation it usually makes sense to just make the magnetic field rotate in the stator and keep it fixed in the rotor. That way you avoid putting hot electronics in an already difficult-to-cool area that may also need to withstand some serious g forces. But you do need some way to magnetize the rotor (setting aside reluctance motors) so that probably means permanent magnets, an induction-powered electromagnet, or a conduction-powered electromagnet (via slip rings). Old-school DC motors use commutators in times and places where electronic commutation is too expensive or hadn’t been invented yet. I’m not aware of any configurations where the commutator creates a field that rotates relative to the stator, probably because you’d need to send the power into and back out of the rotor so there are twice as many parts to wear out.

hristov 4y ago

Using brushed motors in 2023 is really stupid. Yes I know there is a semiconductor shortage, I know Silicon Carbide is expensive and silicon is not very efficient. But seriously. Batteries are also expensive. And brushed motors are very inefficient. This is just another sign that BMW is way behind in electrification.

nerpderp82 4y ago

I think this might validate Neil Saiki's (no longer with the company) view on brushed motors for their electric motorcycles (Zero Motorcycles). https://www.youtube.com/watch?v=0hQ7S3QPSpI https://www.youtube.com/watch?v=0hQ7S3QPSpI They later moved to brushed motors, but I believe that was more for customer demand and not a direct engineering reason. Who knows of the exact solution for brush lifetime in the BMW motor, but one could absolutely have a sweeper, a reservoir and brushes that could last 1M miles or more. Maybe the solution is to have brushes in a cartridge that could be replaced. Only an engineering problem. If the major ingredient into your system is iron, your asymptotic cost is lower than $1/lb. I really appreciate Neil's engineering ascetic, it seems brutally honest.

sandworm101 4y ago

I wonder how much of this is due to legal issues. By switching to brushless, do they avoid and of the recent patents re the brushless motors that have dominated EVs?

DakotaR 4y ago

That's really interesting that they picked brushes; Renault's EESM motors are similar but use wireless power transfer to excite the rotor windings. Maybe brushes can pass more current cheaply?

creeble 4y ago
Yes, brushless necessitates more rotating mass plus the loss in the wireless exciter. Longer life (no brush changes or slip ring wear), but lower efficiency. I wonder if a hybrid rotor would pay off? It would still need brushes, but the current could be less to make them last longer. Probably a problem with demagnetizing the fixed magnets or something.

752963e64 4y ago

[dead]

seanhunter 4y ago

BMW are very good at innovations using old/unfashionable tech and are happy to sometimes be a bit eccentric/different from everyone else. I have a BMW motorcycle with a "Boxer"[1] engine which is the product of a process of continuous refinement of an original 1923 design. It's an amazing engine design that is almost completely unknown outside of BMW. On the other hand, my old BMW motorcycles had a design for the indicator controls that everyone in the industry found really weird and ended up being abandoned[2] [1] Horizontally opposed twin cylinder https://www.carolenash.com/news/bike-news/detail/a-brief-history-of-bmws-boxer-engine https://www.carolenash.com/news/bike-news/detail/a-brief-his... [2] I actually liked the old design but w/e

deleted 4y ago
[deleted]

WirelessGigabit 4y ago

Replacing the brushes as they wear out: fine. But what about the dust accumulating inside and sticking everywhere, adding additional wear. I guess we'll see how many iXs are still on the road in 5 years.

darksaints 4y ago
It uses slip rings like your alternator, not a commutator like a typical brushed DC motor. I’ve had alternators that have lasted more than 20 years, and they don’t have dust problems. There’s no arcing and there is a continuous contact surface, so there isn’t really any dust.

rajnathani 4y ago

> ..there's no turning permanent magnets "off. " Their magnetic fields never change, so when they're not being powered by energy in the stator winding, they're generating energy in those windings, which creates drag. This is why some EVs powered by multiple motors either use a clutch to decouple and idle a permanent-magnet motor when it's not needed, or they fit one asynchronous AC induction motor (which suffers no such losses) and one permanent-magnet motor. This part is really interesting from a physics energy (thermodynamics?) standpoint.