General Question

LuckyGuy's avatar

For those of you with electric vehicles, do you notice a vibration when you are moving at low speeds?

Asked by LuckyGuy (38415points) 1 month ago

Electric motors using permanent magnets are efficient but do not have perfectly smooth torque at low speeds. This variation is called “cogging torque” and it results in a mild vibration that is felt through the car at very slow speeds.
If you have an EV, do you notice this cogging when you’re driving slowly like creeping in traffic or in a parking lot, or moving in and out of your garage? Do you find it objectionable? Did you even notice it?

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10 Answers

gorillapaws's avatar

I haven’t felt this. My Model 3 is buttery-smooth unless it’s going over rough pavement. You feel the road (by design), but never the motor. I have driven a Model X and haven’t experienced this either. Those are the only EV’s I’ve ever driven.

LuckyGuy's avatar

@gorillapaws Thanks. The Model 3 electric motor does not use permanent magnets so it is slightly less efficient and slightly lower cost. But theoretically it can be made to run as smooth as silk.
If you are creeping (under 5 mph) in traffic you don’t feel anything? The cogging torque pulsations in a permanent magnet design are in the 4 to 5 Hertz range.

gorillapaws's avatar

@LuckyGuy “If you are creeping (under 5 mph) in traffic you don’t feel anything?”

I honestly don’t. I’m usually in Autopilot though when I’m creeping like that, so I might be more disconnected from those kinds of vibrations. My experience though really has been silent and smooth except for the Millennium Falconesque noise it makes when you stomp it. Maybe they’ve isolated the vibrations? or maybe it’s tuned to prevent them somehow? I saw a video of what’s inside a Model S motor and and I was shocked at how many PCB’s were in the casing. It’s like a Bitcoin mining operation. Maybe some of those 1’s and 0’s are being used to address the vibrations?

I’ll creep around sometime this week, paying close attention to vibrations and report back if I feel anything that you’re describing.

LuckyGuy's avatar

@gorillapaws i think you just explained why Tesla stock keeps going up even though they are not making money and have such small production. When the cars are not driving Elon is using the idle processing capability in the transmission to mine bitcoins. Each night the car phones home to the mother ship and downloads the results. How else can you explain the mandatory connectivity requirement?
(I expect to see this on QAnon shortly.)

crazyguy's avatar

@LuckyGuy LOL

I am always in autopilot mode when stick in slow and stop driving. In four years of driving a Model S, and a year or so with the Y and once with a Model 3, I never felt vibrations as you describe, although my old Model S did have some noise issues. Funnily enough, my wife never heard anything in the original Model S even though her hearing is far better than mine.

LuckyGuy's avatar

To be clear, the older electric motors are not permanent magnet type and should not have this kind of issue. Permanent magnet motors are on the horizon due to their higher efficiency which translates to higher power, longer battery life, and extended range. But, they necessarily have the cogging torque issue. There is some serious R&D taking place now to reduce this effect.
i just wondered if anyone with any EV has noticed it.

gorillapaws's avatar

@LuckyGuy I’m pretty sure the Model 3 uses permanent magnet motors unless I’ve got bad info.

This article talks about the motor also.

Brian1946's avatar

@LuckyGuy

Do you drive a Tesla?

LuckyGuy's avatar

@Brian1946 No. i do not. I live in western NY – a cold climate with snow. I have Subaru Forester.

SquirrelEStuff's avatar

I do not notice this in any of my EVS. I have a Volt, Clarity, and I-Pace.

Are you sure you are not feeling the regenerative braking?

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