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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 commuta

by 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.
  - sandworm101 4y ago
    >> making combustion engines which aren't reliable in the long term. Who? Which engines are not reliable over 5/7/10+ years? Fiat? Some custom thing built in a German garage? All the big manufacturers are churning out amazingly reliable IC engines. Almost anything from Honda/Toyota/BMW/Merc will last decades. Maybe some sensor needs replacing or an electrical circuit has an issue, but with normal maintenance modern IC engines go forever, far longer than most new car buyer ever keeps the vehicle. The air conditioning, cruise control, radio, suspension, transmission and seat cushions will all be dead long before the engine gives up the ghost. What breaks are things like sensors and control systems, little inexpensive parts that are generally worthless compared to the effort needed to diagnose and replace them. And that isn't going away with EVs. They have basically the same number of drivetrain sensors and systems as any IC car. Taking the car into the mechanic because of an engine light will still be a thing.
    - nuancebydefault 4y ago
      Maybe you will call the following anecdotal but my car has 280000 km and is completely worn out. Lots of expensive parts already have been replaced, including engine wiring. It's not a cheap Fiat but a more expensive Mazda. No, cars in general (the medium price segment, family cars) are not made to last much more than 10 years. One good reason for that fact is that the used technology becomes obsolete after that time. Another reason is fashion, people don't want to be related to an old car. Another one: they need to be as light as possible, hence sturdy enough but not military grade. Another, labour is expensive, so preferrably maintainance every 20k km or once a year. Cars have lots of pieces that don't need maintenance, e.g. ball bearings, but instead need replacement every x years. Same with the engine, nobody wants to bother with an expensive revise of that part. Electronics, the PCB boards/components are not produced anymore beyond 10 years. The list goes on. ICE or electric, the same arguments apply. Thinking of it, the same life expectancy holds for many appliances.
- iSnow 4y ago
  That begs the question why cars up until roughly the early 90's had an expected life time of 10-15y and have increased life expectancy now. Surely, it can't be hard to engineer parts of the engine or the chassis in a way that it breaks/corrodes after 10y. In fact, before zinc was used to protect the metal, that was one of the limiting factors. I think the answer is competition, and I don't see why there should be less competition for BEVs which are simpler to construct than ICE cars. Additionally, some managers claim that real-world battery life is much longer than expected, see https://www.forbes.com/sites/carltonreid/2022/08/01/electric-car-batteries-lasting-longer-than-predicted-delays-recycling-programs/ https://www.forbes.com/sites/carltonreid/2022/08/01/electric...
- greenthrow 4y ago
  This is nonsense. BMW has said the brushes in the motors should last roughly 15 years and the motors have been engineered to make replacing the brushes a fairly simple service.
sandworm101 4y ago
Unlike bake pads, these brushes are conductive. So their dust should react to magnetic fields, which are everywhere in these motors. I would expect the dust to settle or cake onto any number of other metal surfaces rather than drift through the air like brake pad dust.
- mkj 4y ago
  Or add magnetic plugs to capture the dust. https://www.lislecorp.com/oem-products-division/magnetic-plugs/ https://www.lislecorp.com/oem-products-division/magnetic-plu...
- cpuguy83 4y ago
  Even the title says "No magnets"
  - sandworm101 4y ago
    No magnets doesn't mean no magnetic fields. I believe they were referring to permanent magnets. An electric motor without any magnetic fields would be a very odd device.
    - sbaiddn 4y ago
      And a motor with a static magnetic field is just as weird.
      - sandworm101 4y ago
        Ion drive thrusters. Not sure how one would translate them into a car, although there have been some on model aircraft, but they are a type of motor with a static magnetic field.
    - cpuguy83 4y ago
      Thanks for the clarification!
- entropicgravity 4y ago
oakwhiz 4y ago
Makes me wonder how "enclosed and sealed" this compartment is. On various types of motors there is actually an access hole that allows you to change out the brushes. If I was evil I would just seal up that huge motor, weld it shut and never allow the brushes to be swapped out, but I'd put a check engine light when the brushes start to wear down so that the customer has to buy a whole new motor.
dhosek 4y ago
There’s a brushed electric motor in your refrigerator. How often does that need to get serviced?
- GeorgeTirebiter 4y ago
  Yes, and that motor operates in a practically constant external temperature and likely fairly constant humidity, with very few shakings of the environment in which it operates - it's about as optimal for electric motor use case that could be imagined. A car's motor is in the elements, and gets bumped around and otherwise has to keep working in a non-optimal environment. I'd say if motor survives 15 years, that's plenty, as the kinds of folks who buy BMWs tend to buy new at least every 10 years, I suspect. The OTHER thing people I think are missing in this discussion is: how much OTHER car tech is going to improve over, say, that 15 year time? Advanced driver safety tech alone may make buying a new car a wise choice, vs servicing an older, less-tech-capable vehicle, for certain market segments.
mndgs 4y ago
While true, there's other stuff that generates much more tiny dust particles - tires. Heavy vehicle tire rub is cause to roughly 1/3 PM2.5+ air polution, considering all sources. (Used to work for a exhaust emissions systems manufacturer, I remember reading studies about this, can't give you source now). So, the small particle dust from such motors, I imagine, is a minuscule source to air polution, compared to tire abrasion.

by tromp 4y ago

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.
- sandworm101 4y ago
  >> making combustion engines which aren't reliable in the long term. Who? Which engines are not reliable over 5/7/10+ years? Fiat? Some custom thing built in a German garage? All the big manufacturers are churning out amazingly reliable IC engines. Almost anything from Honda/Toyota/BMW/Merc will last decades. Maybe some sensor needs replacing or an electrical circuit has an issue, but with normal maintenance modern IC engines go forever, far longer than most new car buyer ever keeps the vehicle. The air conditioning, cruise control, radio, suspension, transmission and seat cushions will all be dead long before the engine gives up the ghost. What breaks are things like sensors and control systems, little inexpensive parts that are generally worthless compared to the effort needed to diagnose and replace them. And that isn't going away with EVs. They have basically the same number of drivetrain sensors and systems as any IC car. Taking the car into the mechanic because of an engine light will still be a thing.
  - nuancebydefault 4y ago
    Maybe you will call the following anecdotal but my car has 280000 km and is completely worn out. Lots of expensive parts already have been replaced, including engine wiring. It's not a cheap Fiat but a more expensive Mazda. No, cars in general (the medium price segment, family cars) are not made to last much more than 10 years. One good reason for that fact is that the used technology becomes obsolete after that time. Another reason is fashion, people don't want to be related to an old car. Another one: they need to be as light as possible, hence sturdy enough but not military grade. Another, labour is expensive, so preferrably maintainance every 20k km or once a year. Cars have lots of pieces that don't need maintenance, e.g. ball bearings, but instead need replacement every x years. Same with the engine, nobody wants to bother with an expensive revise of that part. Electronics, the PCB boards/components are not produced anymore beyond 10 years. The list goes on. ICE or electric, the same arguments apply. Thinking of it, the same life expectancy holds for many appliances.
iSnow 4y ago
That begs the question why cars up until roughly the early 90's had an expected life time of 10-15y and have increased life expectancy now. Surely, it can't be hard to engineer parts of the engine or the chassis in a way that it breaks/corrodes after 10y. In fact, before zinc was used to protect the metal, that was one of the limiting factors. I think the answer is competition, and I don't see why there should be less competition for BEVs which are simpler to construct than ICE cars. Additionally, some managers claim that real-world battery life is much longer than expected, see https://www.forbes.com/sites/carltonreid/2022/08/01/electric-car-batteries-lasting-longer-than-predicted-delays-recycling-programs/ https://www.forbes.com/sites/carltonreid/2022/08/01/electric...
greenthrow 4y ago
This is nonsense. BMW has said the brushes in the motors should last roughly 15 years and the motors have been engineered to make replacing the brushes a fairly simple service.

sandworm101 4y ago

Unlike bake pads, these brushes are conductive. So their dust should react to magnetic fields, which are everywhere in these motors. I would expect the dust to settle or cake onto any number of other metal surfaces rather than drift through the air like brake pad dust.

mkj 4y ago
Or add magnetic plugs to capture the dust. https://www.lislecorp.com/oem-products-division/magnetic-plugs/ https://www.lislecorp.com/oem-products-division/magnetic-plu...
cpuguy83 4y ago
Even the title says "No magnets"
- sandworm101 4y ago
  No magnets doesn't mean no magnetic fields. I believe they were referring to permanent magnets. An electric motor without any magnetic fields would be a very odd device.
  - sbaiddn 4y ago
    And a motor with a static magnetic field is just as weird.
    - sandworm101 4y ago
      Ion drive thrusters. Not sure how one would translate them into a car, although there have been some on model aircraft, but they are a type of motor with a static magnetic field.
  - cpuguy83 4y ago
    Thanks for the clarification!
entropicgravity 4y ago

oakwhiz 4y ago

Makes me wonder how "enclosed and sealed" this compartment is. On various types of motors there is actually an access hole that allows you to change out the brushes. If I was evil I would just seal up that huge motor, weld it shut and never allow the brushes to be swapped out, but I'd put a check engine light when the brushes start to wear down so that the customer has to buy a whole new motor.

dhosek 4y ago

There’s a brushed electric motor in your refrigerator. How often does that need to get serviced?

GeorgeTirebiter 4y ago
Yes, and that motor operates in a practically constant external temperature and likely fairly constant humidity, with very few shakings of the environment in which it operates - it's about as optimal for electric motor use case that could be imagined. A car's motor is in the elements, and gets bumped around and otherwise has to keep working in a non-optimal environment. I'd say if motor survives 15 years, that's plenty, as the kinds of folks who buy BMWs tend to buy new at least every 10 years, I suspect. The OTHER thing people I think are missing in this discussion is: how much OTHER car tech is going to improve over, say, that 15 year time? Advanced driver safety tech alone may make buying a new car a wise choice, vs servicing an older, less-tech-capable vehicle, for certain market segments.

mndgs 4y ago

While true, there's other stuff that generates much more tiny dust particles - tires. Heavy vehicle tire rub is cause to roughly 1/3 PM2.5+ air polution, considering all sources. (Used to work for a exhaust emissions systems manufacturer, I remember reading studies about this, can't give you source now). So, the small particle dust from such motors, I imagine, is a minuscule source to air polution, compared to tire abrasion.