Tesla Motors current and future battery degradation warranty...

[bonnie]

No, it wasn't directed at any specific person. It was directed at general discussion throughout the thread that the general public was not aware that batteries would degrade and there was a responsibility to make sure they knew this fact.

 

[Kevin Sharpe]

I am constantly seeing people say in reaction to discussions about battery degradation "Ohh well the 'Infinite Mile Warranty' means you don't have to worry about that."

That is my experience in the UK.

 

[breser]

No, it wasn't directed at any specific person. It was directed at general discussion throughout the thread that the general public was not aware that batteries would degrade and there was a responsibility to make sure they knew this fact.

I just reread this thread. I don't see anyone saying that at all. Kevin has implied that he didn't know about it over on his thread, perhaps your reply was intended for that thread (which certainly has had that line of discussion).

 

[bonnie]

Yep, sorry. The thread has split into two discussions.

 

[smac]

TBH I foolishly expected the warranty to be for 120,000 miles (I have a 60), and didn't give the range degradation a second thought, assuming the thermal management of the batteries made the range losses minimal.

Am I subsequently worried about my car's range whilst I own it ? Not at all, one of the reasons I bought a 60 is I really don't do many miles. I just liked the S as a nice place to be and a handsome looking car to do my daily commute.

Am I more worried about future resale values now? Yes, of course! As I'm unlikely to do 25K miles in mine over 3 years, if mine is a "good one", like some examples I've already seen losing 3 miles over that distance, I should still have a standard range of over 160+ miles.
If I'm unlucky enough for my standard charge to drop below 150 range it crosses a perception threshold, I suspect it will have a disproportionate drop in value.

Of these two theoretical cars which would you buy on the second hand market for the same price?

 

[Doug_G]

Should Tesla cover range degradation? I don't know. I think it might be hard to define what they would cover and not cover due to the variety of ways the battery can be used. Being more up front about the warranty might force them to do something if it hurt sales. But I think in the end the company would be stronger for it. I would no longer have to tell people they should realize that the range is not warrantied.

There are basically three ways the range of your pack can go down:

1. Normal deterioration of Lithium Ion batteries. As we've seen from the Roadster and Model S studies from Plug-in America, for Tesla packs this is pretty consistent as a function of usage (Range is a very useful measure, but cycles is more precise). There are cars that are higher and lower than normal, but the scatter isn't huge. I don't see this as a warranty issue; it's simply a usage issue. (ICE cars also have gradual reductions in performance over time; most drivers simply don't notice because they don't have a nice clear readout showing them what is going on.)

2. One portion of the pack (e.g. sheet) can prematurely hard-fail. This may not be immediately apparent to the driver, aside from the loss of capacity caused by the defective sheet being disconnected by the BMS. To my knowledge Tesla has always repaired packs under warranty when this happens. Clearly the warranty should (and does) cover this.

3. One portion of the pack (e.g. sheet) can degrade prematurely. This effectively limits the capacity of the rest of the entire pack, due to the strings all being connected in parallel and min/max voltage levels. This is more of a judgement call - when is the degradation so great that the sheet can be considered "defective".

I would imagine the complete failure of an individual cell would be a failure. Or perhaps given the large number of parallel strings, Tesla may allow for a certain number of strings to be switched out due to failed cells. In that case a certain minimum number of disabled strings would be deemed a failure.

Given the Plug-In America statistics I find it hard to believe that a sheet would otherwise degrade at a significantly different rate than the other sheets. The exception would be when a single sheet was replaced. Tesla replaces sheets with ones that have similar usage. But they might not be able to get a perfect match; if they selected one that was much more "used" than the others it would ultimately end up limiting the capacity of the entire pack. (Maybe this is Kevin's issue?) At this point we are definitely in a grey area.

 

[omarsultan]

That is a very interesting data point. Impressive. Based on my TMC reading over the past year I suspect a lot of the range "loss" some are reporting is because the algorithm cannot accurately calculate range when the car is not regularly charged to over 90%. But many owners worry about how consistently charging the battery to a high level will effect the longevity of the battery. At this point no one knows the answer.

I would agree. The two things I got out of the Tom Sexton (the guy who runs the aforementioned survey):

1) At the end of the day, degradation is tied to number of full cycles you put your battery through, regardless of how you drive/charge (which actually made me a bit more aware of my efficiency, since better efficiency = fewer cycles)
2) If you BMS does not get to see the full range of your battery pack on occasion, its going to lose track of capacity and the its calculations are going to become less accurate.

Omar's Unsubstantiated Theory #1 is that some folks who's battery packs live in a narrow range are faking out their BMS - its losing track of top and bottom since it never sees either. My BMS sees 264 rated miles and 50 rated miles at least once a week so the BMS calculations are more accurate--I am not really convinced my battery pack is actually doing any better than anyone else's pack.

 

[Chickenlittle]

Would like to remind people posting here that the model s battery pack and warrantee are both very different from the roadster battery pack and warrantee the infinite mile warrantee on the model s does not apply to the roadster. The decrease in range that started this issue was in a roadster and not model s. We don't even know which version roadster the decrease was in. I understand that battery management didn't just improve roadster to model s but also roadster ver 1.5 to 2.0. The roadster battery is cooled by a fluid that is changed, topped off by owner there is no comparison between the cars

 

[cpa]

It would seem to me a sensible approach for Tesla to adopt after they have compiled enough data on real degradation would have a "pro-rated" degradation warranty. We see these all the time with ICE cars for tire wear and 12V batteries.

Tesla could create their "accepted" degradation ranges for cars over a certain age and over a certain mileage. For example, a 5-year old Model S with 75,000 miles might have a degradation parameter of up to 12%. Between 12.1% and 15% maybe 80% is paid by the owner and 20% covered by warranty. Between 15.1% and 20%, maybe the repair/replacement is covered 50-50, and so on.

Cap'n Zap correctly pointed out that there is an enormous amount of ignorance and misinformation out there when it comes to BEVs. If we assume that the Gen III car is going to be as popular as we hope and believe, this ignorance will explode in Tesla's face when new owners suddenly "lose" 10 miles of range under normal circumstances after 5 years. It could become a public relations nightmare and a legal headache if Tesla does not clearly spell out "expected" performance in battery health vs. degradation.

Better to lose a few sales at the outset through clear and definitive information and standards than to deal with the problems when/if they arrive by remaining silent.

 

[spaceballs]

We don't even know which version roadster the decrease was in.

It's in his thread, there is a picture that shows 2.0.

 

[Kevin Sharpe]

there is no comparison between the cars

Thats a matter of opinion and only time will tell just how much of an improvement the Model S is.

We have a separate thread (here) if anyone wants the detail but the implication that my 2.0 Roadster has not been cared for, or is in someway sub-standard is ludicrous. Tesla motors have fully serviced and maintained the car from new over a four year period, and no expense has been spared. Indeed the last Tesla technician to drive it described it as the best Roadster he had ever driven.

Lets try and remain on topic by keeping everything realistic and answering the fundamental questions we have about battery degradation warranties for the Model S and all new products.

 

[bonnie]

Lets try and remain on topic by keeping everything realistic and answering the fundamental questions we have about battery degradation warranties for the Model S and all new products.

He was on topic, imo. It is extremely relevant to point out that there is different battery chemistry between the two cars, not just a matter of opinion. You've been known to throw out plenty of smoke and mirrors. So why don't you just worry about your own posts and not try to control everyone else?

 

[Kevin Sharpe]

So why don't you just worry about your own posts and not try to control everyone else?

I'm posting because some members may be fooled into thinking that the Roadster is in someway substandard. It isn't and we should all try to understand that we need battery degradation warranties for Tesla to be successful in the future.

 

[bonnie]

I'm posting because some members may be fooled into thinking that the Roadster is in someway substandard. It isn't and we should all try to understand that we need battery degradation warranties for Tesla to be successful in the future.

I see. That intent wasn't at all clear from your previous post. I didn't pick up any tone that implied the Roadster was substandard, but of course, it's subjective. It sounded like you were trying to say something entirely different Thank you for clarifying.

 

[Mitrovic]

I find it hard to believe that people are unaware of EV battery degradation. In the 3+ years of Roadster ownership, I've done countless public events and answered a b'zillion questions. When I first bought the car, I was commonly asked how soon I'd have to replace the battery - and now people register surprise to find that after 30k+ miles, the battery still is in decent shape.

I'm not talking about EV people, but just people off the street. People asking me how I charge the car and does it take a special outlet. And THEY seem to know that batteries degrade.

I've seen some claims by some here on this forum that people are unaware that batteries degrade. While I have no doubt that there are one or two naive people in every crowd, I'm not buying that battery degradation is a hidden fact. The simple fact is that all the EV fud over the last several years has used battery degradation as one of the reasons NOT to buy an electric car. So people always ask about it.

That said, there's nothing wrong with finding the information easily. Just not buying that people don't know.

100% right!

Me too, I have been an ambassador to the EV cars and have talked to hundreds EV enthusiasts and EV sceptics ( including my wife ). My findings:

- I have never met a human being who does not know that batteries degrade ( I think that even my dog knows it ). In fact it is the main point why people are reluctant to buy an EV.

- Everybody I met did know that the Tesla "Infinite miles" warranty is for the drive train only

- Of course it would be great for the customer ( owner ) to have a warranty for the battery, but is it feasible? I do not know.

- I like the possibility of my Renault Zoe to lease the battery. As Renault says if the capacity decreases to a given percentage, they will put another battery in the car.

- My roadster failed to proceed due to a defective battery. Tesla replaced the battery on warranty without any discussions.

- Currently, after 4 years and 50 000 Km, my battery has about 10 % less capacity then at the start. I would never assume that the manufacturer should replace it under any warranty.

 

[breser]

I'm posting because some members may be fooled into thinking that the Roadster is in someway substandard. It isn't and we should all try to understand that we need battery degradation warranties for Tesla to be successful in the future.

I tend to think that the Roadster does not have as good of a battery as the Model S. I expect the Model 3 to have a better battery than the Model S. That's just the nature of the technology, Tesla is going to get better with every design iteration as they learn more. We're not anywhere close to them peaking on improvements. The battery tear down that's happening over on the Model S forums shows a lot of room for improvement (not to say they have a bad design now).

Regardless of any level of quality in the design there is always the chance of problems with the materials or worksmanship. This is of course why we have warranties.

I do agree that battery degradation due to materials or workmanship that does not result in the complete failure of the battery should be covered. Your Roadster warranty clearly doesn't cover that. The S warranty seems not to cover it but is more ambiguous since it lacks the complete failure language that the Roadster warranty has. As such I think Tesla should clarify their position on this and make more of an effort to be clear about this.

I do not however, think that a battery that degrades due to normal use has to be warrantied. As others have pointed out ICE vehicles lose range, of course the difference is that ICE vehicles losing range is much more hidden by faster refueling and better infrastructure. Additionally, it's much easier to get a sense of how much repairing and ICE is going to cost. We really have no idea how much a battery pack replacement costs out of warranty. This makes the normal degradation risk difficult to quantify. One solution would be for Tesla to provide a warranty.

I think they will be more successful with a warranty, but like I said I don't think they have to do that. I do think they need to make sure that the public and owners know clearly what is or isn't covered under their warranty. Without that necessary step they risk owners being very unhappy when they run into problems that they expected to be covered and are not.

 

[Chickenlittle]

Thats a matter of opinion and only time will tell just how much of an improvement the Model S is.

We have a separate thread (here) if anyone wants the detail but the implication that my 2.0 Roadster has not been cared for, or is in someway sub-standard is ludicrous. Tesla motors have fully serviced and maintained the car from new over a four year period, and no expense has been spared. Indeed the last Tesla technician to drive it described it as the best Roadster he had ever driven.

Lets try and remain on topic by keeping everything realistic and answering the fundamental questions we have about battery degradation warranties for the Model S and all new products.

1. Never implied or stated that roadster sub standard. It is different. I have both and they are different. It is fascinating to me to see the evolution to the model s. Not just in battery. Most people with model s have probably not driven or looked under the hood of a roadster
2. The model s battery is better. There has been continued evolution of the battery pack. Even early model s can't be charged at the new faster rates of the superchargers. My own and others have noted almost no decrease in the range. Even the manuals between the two cars imply the improvements. There are no warning not to range charge as much as you want in the model s. There is no issue in driving the model s hard, manual clearly states battery will be degraded with extended performance mode in roadster. Even the warranties are so different. Roadster 3 years, 36000 miles versus model s.
3. With your telling us you can no longer do your daily commute, it is a fair question to ask whether you were range charging frequently in attempt to use the car. A question you have not yet answered despite three attempts to get a response

 

[richkae]

Can we actually get this thread to discuss the topic?

If your new car has 265 miles of range and after 1 year and 12000 miles you only have 132 miles of range ( 50% ) do you think you should get a new battery via warranty?
I can not imagine anyone disagreeing with that. But nowhere in the warranty does it say you are entitled to a replacement in such a case.

Once we agree on that then we are just trying to decide what the exact terms should be.

I am a huge Tesla booster, I own stock and 2 cars, and plan to buy more. But I can not in good faith recommend Tesla to everyone without telling them that they may experience range loss, I have no idea how much it will be, and I have no idea how much it will cost them to replace their battery when it happens. I really hate that.

 

[Doug_G]

That's an exaggeration. Look at the Plug-In America graphs. They tell the story. Given the battery technology being used, there's no way the pack would degrade to 50% after 12,000 miles. It's simply not going to happen unless the pack seriously malfunctions, and that would be covered by Tesla.

 

[ElectricLove]

Here's my idea on this, but it requires a completely different thinking process in terms of predicted range.

Currently Tesla (and Nissan, etc.) advertises their vehicles having a particular range, they determine that range by running tests which take the battery from 100% SOC (State of Charge) down to 10% (maybe even less?) SOC which is a cycle that is very abusive to the batteries themselves, if one were to always run their cars from 100% to 10% their batteries wouldn't last as long as if they went from 90% down to 20%. As a long time EV'er I feel strongly that we need to stop pushing the batteries to their limits, when I've built and driven EVs in the past I learned there is a huge difference in long-term reliability between a 60% duty-cycle (using 60% of the capacity before charging) and a 90% duty-cycle, so much so that it becomes "ignorant" to ever use a 90% duty-cycle, as such we should never even have it in our minds that it is an option, the manufacturer should not allow it. Think about it like this; does the "Rev limiter" on a Honda Civic allow you to go to 9K RPM? The engine could handle it, a few times, it wouldn't last as long but it could do it... No, the rev limiter doesn't allow you to even get close to that high RPM, because proper engineering includes building in proper safety-nets and safety-tolerances. No EV should ever be allowed to drive a 90% duty-cycle on its batteries, its "ignorant" and John Q. Public shouldn't be expected to know that, its a new type of vehicle, the public is completely ignorant and as the "pioneers" into the industry companies like Tesla are responsible for keeping the technology safe and simple for the consumers, therefore they should limit their batteries to using 70% of total capacity (I think a "limp home" mode starting once the SOC hits 20% would be reasonable but it should be so restrictive that no one would want to regularly enter that mode, just there so you don't "have" to get it towed, this mode would be severely "power limited"). So that is what I think the problem is, on the whole...

The other side of this is the warranty, I think the manufacturer should be completely responsible for range-degradation and I also think its not as big of a problem as they might think, if they properly engineer the vehicles they are selling. The warranty should be 80% of range at initial purchase for 8yrs/100K, I'm guessing 70% would be more likely but I'd rather shoot for the stars and land in the trees than shoot for the trees and land on the ground.

To abate the degradation of batteries Tesla should eliminate "Range mode" charging and change "Range" driving mode to be only power reduction and NOT also include greater battery depletion. Their software should also build in a gradually increasing % of total capacity as usable capacity (up to a limit) to eliminate the consumer from experiencing any reduction in range at all. My example to explain this is: On day 1 a 100kwh battery pack is software limited to 70% (70 kwh) "usable (ie. charge to 90% discharge to 20%), every time the 100kwh value decreases the algorithm to determine the usable energy increases, so after 1 year maybe the capacity is 98kwh but the software is now allowing 71.4% of that as "usable" so they maintain exatcly the same usable 70kwh. At 5 years the pack may have degraded down to 90kwh and the software is now allowing 77.7% of that as usable, still 70kwh usable... ETC, ETC... To a point (maybe at 85% of available energy the software will stop allowing it to increase to prevent further long-term break-down acceleration). The main benefit of this system is that the consumer will see the exact same "range" or "usable kwh" every time they use their vehicle (to a point, maybe 8-10 years later...), when their range actually starts to decrease it would signal to them that it is time to replace the pack OR continue to drive until it becomes too low for function...

I think that sort of safety net should be incorporated by all EV manufacturers and with our newer battery technologies (higher energy density, larger packs) I think its completely reasonable to both protect the batteries from any perceived degradation and still provide desirable/usable range!

I don't think people (in general) need an EV that can drive more than ~250 miles on a charge when there are superchargers/ChaDeMo/ETC charging options available more than they want an EV that will drive the exact same 250 miles 8 years from now as it can drive today...