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BMW using a brushed motor
- Thread starter andy92782
- Start date
I've owned two BMWs: an E39 540i and an E90 335i. Both fantastic driving cars, both impeccably assembled, both ridiculously unreliable after the 4 year warranty expired. I have zero faith that these new EV models will be any different, particularly when the motors themselves have wear items (brushes) buried deep inside.
BMW's Magnet-Less Motor: How Does It Work?
Here's why this old-school technology is back in BMW's newest high-performance EV.www.motortrend.com
My first thought is, "Ah, well of course the Germans would put a wear item deep inside the powertrain that will eventually cost a fortune to replace." Curious to know what others think of this choice of technology.
The BMW motors use 'slip rings' not old school brushes fortunately, and it isn't mechanically commutated (meaning mechanically switched). Unlike traditional brushes there isn't sparking (which is bad with DC).
It's an OK option and has advantage of lowering materials costs for rare earth permanent magnets. Neodymium prices are shooting up and mostly made in China. Also by turning off the rotor magnetization the motor can operate free-wheeling with no-regen like an induction motor, but it's more efficient than induction.
No bashing. I came upon this thread while performing research and felt that I needed to post the actual facts for the record. Otherwise someone else doing research like myself might believe the inaccurate narrative being promoted here. I owned my model S for over 8 years and have a lot of experience with the Tesla community. It is my belief (opinion, generalization, whatever) that most Tesla owners get swept up in spec wars, seek out confirmation bias to dismiss all things non-Tesla, and in the process forget what a quality driving experience feels like. I imagine having Stockholm Syndrome must be a lot like owning a Tesla. Take that for what it's worth—an opinion from someone who once drank the KoolAid.
The xDrive 50 variant has a 6-9 month wait similar to the Ford Mach-e. Seems there are quite a few who want an alternative to Tesla's Model Y and Model X. After test driving the iX I can confidently say that the quality of build, materials, suspension and interior silence blows Tesla out of the water. That's simply a statement about why this Tesla owner of 8+ years decided that car ownership shouldn't be about "death by a thousand cuts" (my catchphrase for the Tesla ownership experience). The M60 is every bit as fast 0-60 as a Model X LR, real-world range is within 10% of the Model X, and the quality is so much higher for a lower price. The supercharger network is meaningless to me for the few and far between road trips that we take.
And before anyone says "but the Plaid is faster", yes it most certainly is. The Plaid destroys the iX in 0-60 acceleration and 1/4 mile time. But the Plaid is also $42,000 more expensive (factoring tax credit) and not an apples-to-apples comparison. In fact, the price is not even in the same league. I can buy an iX AND a Model 3 for close to the same price as a Plaid. My top-of-the-line iX M60 is going to be $110k—less than a LR and I get a $7,500 tax credit, making it overall $12,000 cheaper than the Model X after Tesla's recent and ridiculous price increases. Funny the other brands aren't hiking their prices anywhere near as much.
Judging by the waitlist for this car, BMW is going to have very good sales.
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Coasting is more efficient than regen for longest range. Using regen is only 64% efficient accounting for conversion losses going into the battery and then back out of the battery. In situations when you don't need to stop the car or slow it down, the BMW motor is more efficient. Keeping Tesla's motor in a state where it appears to be coasting—for example, putting the drive selector into neutral or feathering the pedal so energy consumption appears to be zero—actually requires current from the battery to overcome frictional losses due to the magnets interacting with each other.bouba said:
Since you like strong regen you will love the iX. Its regen strength is up to 200 kW compared to the Model 3 Performance's relatively low 75 kW of regen strength. I don't know what the number is for Model X. When you put the iX into D(rive), it defaults to automatic regen. The car will use its cameras, sensors, and GPS location to determine whether the car should coast or use regen, and how much. There is also a one-pedal driving mode (B) that can be used if you want to behave like a Tesla.
Simply pointing this out as an advantage to BMW's implementation. Whether it results in any real-world difference remains to be seen.
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finman100
Member
ya know, when the Supercharger network is poo-pooed, that's all i need to know about one person's use versus hundreds of thousands of other drivers. good on you.
JustJohn
Member
I have personally never used a SC because I charge at home as well. Probably, there are more than 2 people in the same situation.
I'd certainly like to see a better charging network for the East coast in general but I would have very infrequent cause to use it.
thesmokingman
Active Member
Coasting is also illegal downhill. You'll also fail a license test if caught coasting. Going brushless for something of this purpose is not the way to go about it, And they won't answer the question to maintenance, which tells me all I need to know.
The Tesla network on the east coast is pretty good. Do you have a specific location in mind, or are you talking about the CCS network?
No - it's not. Coasting in Neutral, in California, is an infraction. But "Coasting" is not illegal.
thesmokingman
Active Member
It's implied in neutral which is one of the tenets of their move to brushed motors.
finman100
Member
have you seen plugshare comments on other non-Supercharger EV charging stations? it's...er...not good. and hasn't been since forever.
but yes 2 drivers indicates a trend. okay then.
but yes 2 drivers indicates a trend. okay then.
Brando
Active Member
BMW i3 just plain ungly IMHO. BUT it was very advanced for carbon fiber manufacturing.
Sadly BMW dropped all these carbon fiber advancements. Constant improvements? NO.
side note: BMW i3 Archives - Munro & Associates, Inc. ~27,000 pages of reports from Sandy Munro group PDF download only $10. Any auto engineer or anyone wanting to explore vehicle (and carbon fiber) manufacturing should get.
R for Race only runs backward
N for Night and car won't move
D for Day seems to work fine
So I can only drive during the day.
any other Tesla owners having these problems with out of warranty cars? /s
Sadly BMW dropped all these carbon fiber advancements. Constant improvements? NO.
side note: BMW i3 Archives - Munro & Associates, Inc. ~27,000 pages of reports from Sandy Munro group PDF download only $10. Any auto engineer or anyone wanting to explore vehicle (and carbon fiber) manufacturing should get.
R for Race only runs backward
N for Night and car won't move
D for Day seems to work fine
So I can only drive during the day.
any other Tesla owners having these problems with out of warranty cars? /s
That is a mischaracterization of my statement. For those who are interested in having an actual discussion, this was my statement: "The supercharger network is meaningless to me for the few and far between road trips that we take."
Hopefully you can see the difference between hyperbole (yours) and the actual statement (mine), which is about my individual situation.
"Coasting" in the context of my previous post was about how the motors work when there is no current/load applied. It was not stated as a style of driving. I don't think conflating the two is useful here, especially when I'm pretty sure you know the difference.
It's implied in neutral which is one of the tenets of their move to brushed motors.
Is it one of BMW's tenets? I don't see that anywhere. All of my research points to BMW using these particular types of motors in order to be more environmentally friendly and be less dependent on China for neodymium. I am simply pointing out the benefits to this approach (less resistance losses, less current needed to maintain speed) since nobody here, prior to my posting, was willing to engage in factual conversation. The hyperbole is strong.
The iX is made from aluminum space frame and carbon fiber. In fact, you can see the carbon fiber portions of the vehicle frame when you open any of of the doors or the rear lift gate. Here is an illustration that breaks down the different sections of the car's frame. You will also see significant portions that are made from castings.
Your characterization of the transmission reminded me of this Brother Dave Gardner gem:
Look I appreciate a car with good dynamics as much as the next guy. But as much as I agree Tesla could do well to hire some better suspension engineers, I don’t think a 6000 lb SUV is going to be particularly capable around twisties either. Especially since handling hasn’t been modern BMW’s priority either. Asides for the M cars, “Jalopy” is exactly how I’d describe the handling of most newer BMWs.I get that this is a Tesla echo chamber and to expect irrational negativity towards other brands, but the banter here couldn't be more uninformed. BMW's motors are 3-phase AC synchronous motors and the brush is of a slip ring design that only delivers a small DC excitation current to the rotor. It's nothing like the "DC brushed motors" that some here are using as comparison. BMW's radical new design allows for very fine control of power and torque—far more than Tesla's induction motors. BMW's design also allows for true coasting that is impossible with magnet motors.
The part in question is also located on the side of the motor that is accessible for servicing. How serviceable are Tesla's drive units?Model S goes through an average of one motor replacement every 25,000 miles. There is something seriously wrong with Tesla's design and engineering. My impression of Tesla engineering is a room filled with farting teenagers playing video games.
BMW's magnet-free design is more resilient to supply chain issues and less reliant on China. The less anyone depends on China the better. There are no rare earth metals used in the BMW iX. To head off the poorly informed, the lithium and cobalt used in batteries are not rare earth metals. China is the #1 producer of rare earth metals used in magnets, such as neodymium.
The Tesla faithful point to a marginally faster 0-60 time for their favorite brand, but what they neglect to mention is that no Tesla has a properly designed suspension to actually handle that acceleration. The suspensions are identical whether you get the base model or the P. The only difference is the P might be a few tenths of an inch lower, which on its own does not create a performance suspension except in Tesla's imagination.
The car least capable of handling its power output is the Plaid. Try some cornering in that jalopy and you'll know what I'm talking about. It can't even hold a straight line when accelerating due to torque steer. This is due to poorly designed suspension geometry and vehicle dynamics. To get decent braking for a Plaid you have to spend $20k on upgraded brakes that other performance brands already include.
This one-time Tesla owner and fan sold his Model S and ordered a BMW iX M60. I did it over the phone with the local BMW dealer. No markup. No BS. And no reservation fee! I can no longer support a company like Tesla, where a true performance driving experience and vehicle dynamics don't even make it onto Elon's to-do list. The non-existent sound dampening and rough suspensions in Teslas should be embarrassing to all of you. Keep patting yourselves on the back for making misinformed comments.
The car ownership experience and thrill of driving encompasses far more than just a fast 0-60 time. People who value quality materials, fit and finish, build quality, and a refined driving experience will not buy a Tesla. My client dumped his Model S in favor of an Audi e-tron GT and he's never looking back. He said his Tesla was a dumpster fire by comparison. And before you take another swig of koolaid and start quoting the e-tron's EPA range, you probably had no clue that real-world range is closer to 300 miles and significantly higher than EPA rating. Tell me, how many of you have actually hit Tesla's EPA range, ever?
It might behoove some of you to open your minds. Maybe it's been so long since you've driven a properly designed vehicle that you no longer remember how that feels and sounds.
I do agree the performance / plaid teslas should get something akin to the M treatment with more solid suspension, replacing some bushings with ball joints or solid mounts, bespoke shocks / springs etc. But until BMW makes a real M EV, it’s a bit of a moot point.
Tesla owners:
The iX 50 (not even the "real M EV" M60 version) handles far better than any Tesla. I don't know what BMW is doing with the suspension but it's light years ahead of anything Tesla is able to hobble together. You should go drive one if you aren't afraid of falling out of love with your Tesla.
German EVs are less expensive than Teslas. Win win.
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