BMW using brushed motors
- Thread starter Vercingetorix
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OVERKILL
$100 Site Donor 2021
Interesting. Gives a "service" component of course, as those will need to be replaced at some point.
JHZR2
Staff member
Good for them. Permanent magnets are going to be another supply chain issue. Using an induction machine allows for them to actively manage their fields and thus their regen power for different coasting/braking scenarios.
I too question the cleanliness of a brushed motor, but I’m sure everyone is thinking the same so there are eyes on the problem…
I too question the cleanliness of a brushed motor, but I’m sure everyone is thinking the same so there are eyes on the problem…
I wonder why they have to go brushed motor instead of brushless. If anything they could just use AC motor like many other EVs out there. Sure you need to spend some money on the power electronics and various sensors to control your AC motor, but that's pretty much a given even if you use a brushed motor. Is it just a shortcut for BMW to get the power they need without massive R&D? or is it a "German Engineering" thing overcomplicating a problem?
Without the cutout of their designs I can't tell what they are doing, maybe a brush to excite the inner coil as a "permanent motor" then decouple the "brush" at high rpm so they act more like an AC motor?
Without the cutout of their designs I can't tell what they are doing, maybe a brush to excite the inner coil as a "permanent motor" then decouple the "brush" at high rpm so they act more like an AC motor?
I still remember the shortcut they took on i3.
Brushes and slip rings rather than brushes and commutators if I understand correctly, just like an alternator being used as a motor.
Commutation is still done in the field as with a PM motor.
Commutation is still done in the field as with a PM motor.
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Very nice article. I won’t question bmw they know what they’re doing.
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Wonder if they’ll design a removable housing for containing the brush particles. Maybe another filter for the market. 
edyvw
$50 site donor 2025
Most didn’t read article. That is what I am getting out of this thread.
I did read the article before posting my comment to see their reasoning. Most of it is just hogwash. Having brushes in there means they'll be limited and "life of the vehicle" in their words means many things. I doubt they'll make the brushes last 300k+ and if they don't It won't be cheap and easy to replace.
OVERKILL
$100 Site Donor 2021
German cars are notorious for having things replaced on schedules. Usually those things are actually pretty easy to replace. I suspect that will be the case with these, there will be a brush "kit" that perhaps includes a new housing, that you'll be required to have replaced at a specific interval.
Read the article. Basically they said they can get better power/performance vs brushless. They also mention the technology is "greener" because it doesn't rely on rare-earth magnets. I'm calling BS on that one because the biggest elephant in the room regarding rare earth elements is the battery pack. From my experience with the brand (20 yrs) they've probably managed to gain better performance along with the required planned obsolescence. Who knows how long the motors will last. 150k miles? 200k miles? BMW is a "luxury performance brand" so it'll be interesting to see how their motor technology compares to the rest of the industry (Tesla, VW, Hyundai, Ford, etc).
As long as its diy-able and hopefully no more than a couple hundred i wouldn't be upset myself. ill just chalk it up as brake pads. but if they last 60k and cost near a thousand since the dealer has to do it then its a problem.
That's what i was thinking. The battery pack itself is nasty. And i know that cobalt free chemistries exist and tesla is beginning to use it but the lithium is still a huge environmental issue and on top of that you cant go to any shop outside the dealer to rebuild a pack. Ev packs are not easily recyclable either.
But the most important thing is the efficiency. Power is not an issue and i call bs on this. Ev's suffer from efficiency too and need to milk every percent. I wanted to see the efficiency of this motor compared to Teslas synchronous reluctance motor which is the most efficient yet. As if regular ev motors weren't fast enough. They're just making excuses as to why they chose this tech.
Remember that all mining/extraction activities are huge issues at the local level. This includes, oil, natgas, uranium, coal, etc. Battery packs will be repurposed or recycled rather than landfilled. The EU is way ahead of the US in this regard.
yeah the Eu is doing a good job with pack recyclability but right to repair is important for the environment. Having to chuck a pack and put a new one in instead of fixing the existing one is not better for the environment. But the automakers clearly don't want that. They paint it as a safety hazard and dangerous but that's the case in any vehicle if you're dumb. Mercedes is now basically shaming you for opening the hood on their new eqs.
Cant speak for most.
BMW made their choices, and customers get to pick and choose.
The upside is that the unit is more tunable, can freewheel when needed and can avoid potential material sourcing issues - all good upsides.
Skipping potential sourcing issues for the motor means little if you have equal issue elsewhere like say the battery.
Having dealt with brushes on gensets and specific equipment most of my life I chose to avoid that maintenance item whenever possible, not specifying an interval doesn't give me good feeling about this.
What you can send to the motors doenst equal what you ultimately do send to the motors because the battery is another gate in the system - see mustang mach-e gt with its 5 second max to "protect the battery" .
