Electric Motor Warranty - Long Enough Coverage?

Electric Motor Warranty - Long Enough Coverage?

The current M3 warranty for the drivetrain/electric motor for my 2018 M3 LR RWD is 8 years/120k miles.

How long do engineers think the drivetrain/electric motor will last? (Note: Edited to correct info on warranty).

stingray.don | May 23, 2020
geedub1023 | May 23, 2020

+1 stingray.don Thanks....good info!

zerogravitydrgn | May 23, 2020

My understanding is that the 8 year/120k warranty covers the battery and drive unit. The drive unit being the electric motor.

M-A-B-MCMLXXX | May 23, 2020

^ agreed

vmulla | May 23, 2020

I believe the motor will outlast me.

geedub1023 | May 23, 2020

@zerogravitydrgn You are correct. Drive unit, to include motor, are warrantied for 8yr/120k.

Lonestar10_1999 | May 23, 2020

My SR+ was originally shown to have an 8yr/120k warranty on my order page. A few months back it got “corrected” to a 8yr/100k warranty. I am not happy that Tesla isn’t honoring the original warranty but I am hoping I won’t need warranty service on the motor.

Say what you want about the car, but the customer communication and information accuracy has a lot of room for improvement.

vmulla | May 23, 2020

“ Say what you want about the car, but the customer communication and information accuracy has a lot of room for improvement.” @Lonestar10_1999


However, it’s worth mentioning that messaging has improved quite a bit in the past year.

rehutton777 | May 23, 2020

We/ve been through this before. The Tesla Model S, Model 3 and Model X warranty booklet dated February 1, 2019 clearly states "Model 3 with Standard or Mid-Range Battery - 8 years or 100,000 miles (160,000 km),
whichever comes first, with minimum 70% retention of Battery capacity over the warranty period". If you purchased your vehicle after February 2019, the battery and drive unit warranty has ALWAYS been 100,000 miles, irrespective of what any salesman may have told you. Read the published literature.

fazman | May 23, 2020

Performance model 3 and LR i believe offer a longer mileage drive unit/battery warranty but not additional time?

geedub1023 | May 24, 2020

@rehutton777 You missed the main point of my post. It wasn't about the length of the warranty coverage, it was about how long the engineers/experts think the drive unit/motor will last in comparison to the warranty.

M3phan | May 24, 2020

I remember reading that same article @stingray posted. Instilled great confidence, I have to say. Add that to a soon to come million mile battery and wow!

JAD | May 24, 2020

Also changing an electric motor is cheap and easy compared to an ice.

lbowroom | May 24, 2020

Hour long do engineers think ICE drivetrains last? | May 24, 2020

@lbowroom - Hopefully more than an hour?

JAD | May 24, 2020

Well, top drag race engines last ~5 seconds, old F1 engines about an hour, new F1 engines about 10 hours.

Formula E engines are expected to last 2 seasons....

Not really comparable, but ....

Magic 8 Ball | May 24, 2020

When is the last time you had an electric motor fail on anything?

lbowroom | May 24, 2020

About two years ago a bought a new shopvac and the motor seized in the first minute of use.

Sorry for the literal answer... I found humor in it

vmulla | May 24, 2020

geedub1023 | May 24, 2020
@rehutton777 You missed the main point of my post. It wasn't about the length of the warranty coverage, it was about how long the engineers/experts think the drive unit/motor will last in comparison to the warranty.

I don't consider myself an engineer* or an expert, but my original answer was based off my experience across my Teslas. My Model 3 is approaching 70K miles now, and I believe that the mileage based warranty on Teslas is meaningless, the drivetrain is far more resilient than the warranty numbers suggest.

*I have a master's degree in electrical engineering, but I never used those skills professionally - life had something else in store for me :)

lbowroom | May 24, 2020

Anyone feel like explaining mean time between failure?

Frank99 | May 24, 2020

Well, I've also had Shopvac motors fail, but that's because they don't use sealed bearings in the motor . Use it just once vacuuming up dust from cutting concrete, and it's toast. Why they don't spend an extra $0.50 in build costs so they'll last forever...wait, I think I just answered my own question.

Magic 8 Ball | May 24, 2020

Yikes, probably should have qualified with "quality" electric motor.

Magic 8 Ball | May 24, 2020

Never had my craftsman wet/dry shopvac go on me (20+ years old) and it has been through hell. I think it is ready to go tho' since it spent last winter outside without a good cover over it.

lbowroom | May 24, 2020

I did write shopvac but actually whatever brand HD sells. Replacement has been fine.

Tronguy | May 24, 2020

Well, there's the bathtub curve. Not everything follows the curve, but enough does that the concepts in it make enough sense to be useful.
The curve is the probability of fault at a particular time. At T=0, when the product leaves the factory, the probability of error is relatively high due to latent manufacturing faults. This is why a lot of stuff that one buys has that 30-day warranty at the Big Box store; there's a lot of returns during that time when some nut-that-didn't-get-screwed-down right backs off and kills the hardware. Or a defect in the metal after it came out of the vat and was forged comes to bear, the piston rod breaks, and one needs a new motor. Early stuff.
As time goes on these failures drop off. One is then left with random failures, evenly distributed over time. This is usually figured as a Poisson distribution. The failure unit is in FITs: Failures in Ten to the Ninth Hours. A single resistor, for example, is usually figured to have a rating of 1 FIT. If one has a billion resistors lying around, then it's expected that, at room temperature, with the things operating, one resistor fails per hour.
So, say that one has a radio with a thousand resistors in it. That means that, just talking about the resistors in that radio, there's 1000 FITs. So, the failure rate would be 1000/1e9 = 1e-6 probability of failure per hour, on average, across all the radios made by this manufacturer. Or, looking at it another way, given that there's 8760 hours per year, the probability of this radio failing in a given year because of a resistor in it going bad is 8760*1e-6 = 8.76e-3, or about 0.87% per year. Not bad.
But, since we're talking about, say, a table radio, let's say that there's 10 ICs in it. FIT rates of IC can vary a lot; especially hot ones, and it's proportional to the number of I/O on the IC. Let's say these are middle-of-the road and there's each 100 FITs. That's 1000 FITs for the ICs, 1000 for the resistors, 1000 for the other passive components, 5000 for any moving parts, and then we got a vague back-of-the-envelope number for a given radio might be 8000 FITs. Probability of failure of said radio in a year would be 8760*8000/1e9 = 7%. And now you know why radios come with a one year warranty.
Mean Time Between Failures is simply 1e9 divided by the FIT rate. So, for our radio with 8000 FITs, the MTBF is 1e9/8000 = 125,000 hours, or about 14 years.
For those who are interested, FIT rates can be actually measured; there's something called the Arrhenius equation which relates failure rate to temperature. So one will take a large batch of components, crank the temperature to some huge number, then record the failures over a month or three. Then, once the failure rate is measured with this statistically significant number of parts, one can mathematically crank the temperature back down to some more sane number and get the FIT rate at 25C.
Where life gets interesting is when one is interested in building reliable hardware that has protection, so that if one thing fails, there's a backup, with a Mean Time To Repair once the original fault's detected. There's standards for telco gear, for example, that mandates 50 microminutes per year expected downtime. And you don't want to even think about the calculations done for NASA-certified long-haul satellites that don't have any repair possibilities; backups on top of backups on top of backups, with fail-safe all over.
Finally, at the end of this Poisson-distributed flat error rate, one runs into the end of the bathtub curve: Wearout, which is what it sounds like.
An example of an object that everybody knows about that's subject to the bathtub curve are incandescent light bulbs. Get a case of 1000 of them, and power 'em up. Likely that in the first few hours a few will die; then, they'll run for the length of time, roughly, stated on the box, with the rare but occasional random failure; then, since there are processes in play that cause the filaments to erode over time, more and more of them will begin to fail. For a bulb rated at, say, 1000 hours of operation, they'll all likely be dead (probability, remember) around 5000 hours.
But there are things that don't have a wearout mechanism. There are low-power transistors, for example, that, if one doesn't run the electrons around too fast, have no known wearout mechanisms. Start one up today and, assuming one can find a reliable power supply (ha!) it might be running 1000 years from now. Fun.
But if any of you were wondering why the Gen 3 computer in Model 3's have two redundant CPUs.. Now you know.

Tronguy | May 24, 2020

The screwiest thing I've ever heard of with respect to reliability engineering is when a couple of EE PhD's in the field decided, for the fun of it, to look at building a reliability model for the human body. The started off with lots of redundant parts, actuarial tables, some basic biology, and came up with a model. The first whack was to make the model fit (numbers of parts, how long they lasted, etc., etc.) over, say, from year 20 to year 50 for people. They then took the model thus generated and looked to see if they could make predictions with it. Scarily, they could make accurate predictions on probability of death for people from sixty on up that matched what's actually seen in the population; further, they could even make predictions over a population for babies up to 20 or so that also fit actual death rates.

lbowroom | May 24, 2020

Yes, but when will the one I buy fail, so I can apply that answer to all? Lol

rehutton777 | May 25, 2020

geedub1023: "@rehutton777 You missed the main point of my post. It wasn't about the length of the warranty coverage, it was about how long the engineers/experts think the drive unit/motor will last in comparison to the warranty."

My comment wasn't addressed to you - - it was addressed to Lonestar10 who persists in complaining that his SR+ warranty was reduced from 8Y/120K down to 8Y/100K. The warranty booklet published in Feb 2019 shows a battery/drive motor warranty of 8Y/100,000 miles. I agree with others - - based on information I have seen, I'd be surprised if the motor doesn't last years longer after the warranty expires.

Lonestar10_1999 | May 25, 2020

@rehutton777 - my beef with the battery/drivetrain warranty was that my order page showed 120k miles from the day I took delivery and for several months thereafter. Clearly this was not Tesla’s intent, but it was their error.

I am hopeful the battery/drivetrain will not need servicing between 100k and 120k miles but you never know. If so, I would think Tesla would recognize their error and stand behind their product. If not, well that’s why there’s arbitration.

lbowroom | May 25, 2020

How have they not stood behind their product?

jordanrichard | May 26, 2020

Lonestar10_1999 did you print that "120k" ?

Manufacturers can not take away anything from the warranty as it was written at the time of purchase. This is why I highly recommend people print on actual paper, a copy of the owners manual and warranty.