"Fixing E-Motors is all about changing out ball bearings"

[cashcow]

I keep hearing this talk about bad electric motors only needing ball bearings changed out to work as good as new over at tesla reddit. Mainly in the new EXTENDED CPO PROGRAM topic that came up. Its about high millage Tesla Model S getting only 2 years extended warranty instead of 4 I believe. New program. Anyway, someone there keeps saying that when our E-Motors go bad we just have to change the ball bearings. Makes it sound so easy. Is this true and as easy as it sounds? I have read a little on the topic before... but really don't know much. What do you guys think?

Also, he said that when your motor gets swapped on your tesla model s that you get refurbished motors (Ball bearings changed) instead of brand new motors. is this true too?! Does this apply to us also?!

 

[miimura]

There are no new RAV4 EV drive units. If you get yours swapped under warranty, it will be a rebuilt one. What they actually do when they rebuild it is not known.

 

[hbrav]

The problem with the motors apparently was the fact that the induction style motor during operation develops large induced currents in rotor and voltage difference between rotor and motor case causing currents to move towards ground via the bearings opposite the gearbox side (splined end) of the motor. This current through the bearing heats and damages the bearing prematurely leading to the groaning sound that is apparent in bad motors. The fix is to remove the motor and replace the bearing. The Tesla modification to prevent this reoccurring was to place a wiper system on the gearbox side of the motor which provides a path to vehicle ground for the current instead of the bearing. This is the upgrade part of a motor rebuild. Not all motors suffer from this so there are plenty of old motors still running fine at quite high mileages. Another preventative measure would be to place a conductive lube in the gearbox to allow the currents another path. Problems like these are not seen in permanent magnet motors like a UQM or Leaf drivetrain.

This is just a theory but the problem motors do have a bad bearing and its almost always opposite side of the gearbox and replaced units are rebuilt with new bearings and a rotor "brush".

Steve
2012 Rav4 EV "Pearl White"
All Original working fine 53K

 

[TonyWilliams]

Wow, that is an amazingly detailed and rational explanination. Do you work for Tesla or Toyota?

 

[hbrav]

No but I've messed about with the Tesla drivetrains and Richard over at EVTV pretty well covered this problem. Contacts within Tesla have confirmed that motors are rebuilt by replacing bearings and that the noise heard on "damaged" units is coming from said bearing. As to why they actually fail I doubt that Tesla or Toyota would ever reveal the facts, so these are just end of day theories.

That said these RAV vehicles are very easy to fix, modify and maintain I'm not sure what the concern is with warranties and such, just go on Copart and get a wrecked model S and take out the drivetrain, now you have a spare. Seems like hybrids and EVs most insurance work involves "salvaging" perfectly fine electric vehicles.

My background is electronics and software I have worked with a few of the car OEMs employed as ASIC designer, bit of background in BMS semiconductors used in some popular hybrid/ev packs also chargers even have a few related patents. Funny thing is most of the engineers involved with these cars cannot afford to own them so we make our own or get second hand and broken ones. Sure a few dotcom types drive Teslas but its usually doctors, realtors, lawyers etc so usually hard to get good info on these things unless someone like Richard comes along and is willing to pony up the $$s. I have friends at SpaceX and Tesla both drive old GMCs.

Steve
2012 RAV EV "pearl white"
53K miles

 

[Christopher Castagne]

The problem with the motors apparently was the fact that the induction style motor during operation develops large induced currents in rotor and voltage difference between rotor and motor case causing currents to move towards ground via the bearings opposite the gearbox side (splined end) of the motor. This current through the bearing heats and damages the bearing prematurely leading to the groaning sound that is apparent in bad motors. The fix is to remove the motor and replace the bearing. The Tesla modification to prevent this reoccurring was to place a wiper system on the gearbox side of the motor which provides a path to vehicle ground for the current instead of the bearing. This is the upgrade part of a motor rebuild. Not all motors suffer from this so there are plenty of old motors still running fine at quite high mileages. Another preventative measure would be to place a conductive lube in the gearbox to allow the currents another path. Problems like these are not seen in permanent magnet motors like a UQM or Leaf drivetrain.

This is just a theory but the problem motors do have a bad bearing and its almost always opposite side of the gearbox and replaced units are rebuilt with new bearings and a rotor "brush".

Steve
2012 Rav4 EV "Pearl White"
All Original working fine 53K

Two questions:

Is there generally a certain mileage at which this problem manifests in a "bad" motor - in other words is there a mileage at which it is safe to say - if it this hasn't happened yet, it probably wont, or is it that the motors prone to this failure can show it at any time.

Also: How would one go about placing a conductive lube in the gearbox - is this something a technician job and howmuch would it cost?

thanks for the amazingly helpful info

 

[SeattleRav4]

If this analysis is correct, and it makes technical sense and seems to fit the available data, then the answer to "is there a mileage after which you can say, this one is good" is no.
The initial assumption was that the drive units failed due to infant mortality. This thread argues it has always been infant abuse. The sport mode, coupled with the "no alternate electrical path" design would kill the bearings on any vehicle pressed hard in sport mode. It appeared to be infant mortality because sport mode is used most when you first get the car. It is just fun to try out, and with no data to say it was bad, why not.

Since I had my drive unit replaced, I really haven't needed or wanted to use sport mode, so far there is no motor whine. Anecdotal evidence, yes.
The point is if the high induced currents is what kills the bearings, then anyone wanting long bearing life need only not drive with high currents, i.e sport mode.

We will have to hope for more data to see if the new wiper design completely solves the bearing problem.

Anyone will to drive aggressively in sport mode with the new drive unit and see how it holds up?

 

[TonyWilliams]

I very seriously doubt that the relative low load of "Sport" (compared to the load of the same rear motor in a Tesla P100D) has much to do with bearings wearing out / being damaged.

If the drive motor was properly designed, we wouldn't have this thread at all.

Elon Musk had suggested years ago that the problem was some $2 plastic part, which of course was complete BS. It very clearly was bearings, and knowing that the bearings are not metal, it only amplifies the issues.

 

[smkettner]

Electric motors have been around a long time and at far higher voltages and power etc.
Suddenly Tesla invents a new issue? BS meter is off the scale.
Poor design, plain and simple.

This is the #1 reason I did not put a deposit on Model 3. Going to need proof of resolution.

 

[TonyWilliams]

Electric motors have been around a long time and at far higher voltages and power etc.
Suddenly Tesla invents a new issue? BS meter is off the scale.
Poor design, plain and simple.

This is the #1 reason I did not put a deposit on Model 3. Going to need proof of resolution.

There is a combination of a set of relatively new design parameters that probably affect the bearing deterioration:

1) Lightweight, low cost, small

2) Very high power output to weight

3) Inductive motor

4) Non-conductive ceramic bearings

All that power is going through a small bearing(s)

 

[Ev_Bob]

That said these RAV vehicles are very easy to fix, modify and maintain I'm not sure what the concern is with warranties and such, just go on Copart and get a wrecked model S and take out the drivetrain, now you have a spare...

Drivetrain failure is a big sticking point for me when considering purchasing a Rav EV.

Would there be a guide on what it takes to swap out drive train online somewhere? Is it a particular model S drivetrain that is a direct swap? No need to update anything in the software?

thanks!

 

[TonyWilliams]

That said these RAV vehicles are very easy to fix, modify and maintain I'm not sure what the concern is with warranties and such, just go on Copart and get a wrecked model S and take out the drivetrain, now you have a spare...

Drivetrain failure is a big sticking point for me when considering purchasing a Rav EV.

Would there be a guide on what it takes to swap out drive train online somewhere? Is it a particular model S drivetrain that is a direct swap? No need to update anything in the software?

thanks!

What drivetrain "failure" are you referring to? They don't fail... they just get noisy.

 

[Alex UA]

That said these RAV vehicles are very easy to fix, modify and maintain I'm not sure what the concern is with warranties and such, just go on Copart and get a wrecked model S and take out the drivetrain, now you have a spare...

Drivetrain failure is a big sticking point for me when considering purchasing a Rav EV.

Would there be a guide on what it takes to swap out drive train online somewhere? Is it a particular model S drivetrain that is a direct swap? No need to update anything in the software?

thanks!

What drivetrain "failure" are you referring to? They don't fail... they just get noisy.

The input shaft of the gearbox rotates at exactly the same speed as the rotor up to 16,000 rpm, but the usual bearings 6207 / C3 and 6208 / C3 are installed there so they die the fastest.
In addition to replacing bearings on the 6007 rotor with ceramic, we also install on the input shaft during repair
And on the input shaft ceramics: 6207-2RZTN9 / HC5C3WT + 6208-2RZTN9 / HC5C3WT.

the bearings that are mounted on the RAV4 EV and Tesla model S are SKF BB1-3793 they are also ceramic, and they come out not only due to the ingress of the G48 through a worn oil seal, but due to their overheating, in other words, the bearing lubrication loses its properties, which leads to premature wear. and indeed, on the RAV4 EV and Mercedes Benz electric engines they put the most ordinary bearings, then they fit in size and they didn’t bother. this is why we have these problems.

 

[asavage]

See this post on my reasoning why I do not think installing ceramic (electrically isolated) ball bearings on the gearbox input is a good idea.

 

[Promedic]

@ALEX UA:

Why do you use sealed hybrid bearings for the gear?
Original they are without sealing (6207 and 6208)