Roadster battery warranty terms?

Yggdrasill · May 30, 2012

Does anyone know what criteria Tesla uses to judge if there is a fault in the battery of the Roadster, and replace it under warranty?

I'm sure most of you guys know that there have been some fairly hefty discussions concerning remaining range after X years, and a part of this discussion is what value the battery warranties offered by car manufacturers actually has. Here at least, Nissan for instance does not cover "gradual capacity loss", so in theory, Nissan does not replace the battery under warranty even if the capacity is at 5% after a week, provided the loss was "gradual".

Where does Tesla fit into that? Im sure those of you who've bought a Roadster must have some paperwork outlining the terms of the battery warranty. And I've fruitlessly tried to find this paperwork or references to it online.

Personally, I think car manufacturers should develop a standard concering the warranties, so that if a battery is under something like 70% capacity, it is to be replaced under warranty. And then the car manufacturers can set the number of years the battery is covered based on that figure.

strider · May 30, 2012

There are just too many variables to quantify. If you charge in Range mode very day for 3 years your battery will suffer. Should it be replaced under warranty? No, you abused it. But what if you only charge in Range mode every other day, or once/week? What if you use a supercharger every day, every other day, once/week? Legally it's too difficult to think of all the possible scenarios and that could affect battery longevity and place them into a contract. AFAIK (I can check my paperwork when I get home) there is no language in the Roadster warranty about x% after y years or z miles. It says that if there's a defect that Tesla will replace or repair. To my knowledge Tesla has been willing to replace/repair batteries that were marginal as they are learning too. But again, AFAIK it's a judgement call on Tesla's part. My own personal speculation is that they can pull the logs of the car - the Roadster will always report the "weakest sheet" (there are 11 sheets in a Roadster pack). If one sheet stays the weakest for a very long time then it is bad and should be replaced under warranty. However if the weakest sheet changes over time then the capacity loss is gradual and is not a defect.

stopcrazypp · May 30, 2012

Yggdrasill said:
Personally, I think car manufacturers should develop a standard concering the warranties, so that if a battery is under something like 70% capacity, it is to be replaced under warranty. And then the car manufacturers can set the number of years the battery is covered based on that figure.

Any gradual loss in capacity for a lithium battery pack is expected behavior and can't be described as a defect. Therefore most car companies will not cover for that in a warranty. Only when something is unexpected, like the weak sheet strider described, will they possibly cover it. In many cases, it's up to the technician to decide (I know this is the case for the Volt).

The closest thing you get in warranty coverage is that the battery has to provide enough *power* to meet the specs of the car as it was out of the factory. That means for the Leaf the pack has to be able to provide a bit more than 80kW (to run the motor at full bore, plus a bit more for accessories and heat losses). As the pack capacity falls, the max pack power falls in proportion (because max pack power = pack capacity * max C-rate). So if you get "lucky" it might fall under the power needed to run the car. However, most battery packs will be designed to have plenty of power left to spare.

Renault will replace a pack that falls below 75% capacity if you lease their pack (although it's kind of expected in terms of leasing), but I have not seen the actual written warranty. But I doubt an automaker that sells you a pack will specify a capacity in the warranty.

Yggdrasill · May 30, 2012

strider said:
There are just too many variables to quantify. If you charge in Range mode very day for 3 years your battery will suffer. Should it be replaced under warranty? No, you abused it. But what if you only charge in Range mode every other day, or once/week? What if you use a supercharger every day, every other day, once/week? Legally it's too difficult to think of all the possible scenarios and that could affect battery longevity and place them into a contract.

I think car manufacturers should try, at least. Maybe if they neglect to mention some factors in the warranty, they'll have to replace some batteries, but it wouldn't be the end of the world.

I don't see why Tesla, Nissan, etc can't say:

The battery will be replaced under warranty if the battery drops below 80% (minus correction factors) in X years or Y miles. For every 50 uses of fastcharger, the 80% figure is reduced by 1 percentage point. For every 50 times the battery is outside 30-80% SOC, the 80% figure is reduced by 1 percentage point. For every 50 times the battery is outside 15-90% SOC, the 80% figure is reduced by 1 additional percentage point.
For every 48 hours the thermal management system is off due to lack of charge, in an environment outside of -5 and 20C, the 80% figure is reduced by 1 percentage point. If the temperature of the environment is outside -15 and +30C, an additional percentage point is deducted for every 48 hours. If the temperature of the environment is outside -25 and +40C, an additional percentage point is deducted for every 48 hours. (Add any other relevant factors.)

This warranty won't be perfect, but it doesn't need to be perfect either. "8 years, unlimited miles" isn't perfect. There are going to be dozens of taxis in Oslo using a Model S or Model X. These cars can easily be driven over 500 000 miles in 8 years. Will Tesla have to replace some of those batteries under warranty? Most probably. A warranty is an insurance, and is about distributing the risk out to as many users as possible. The idea is not to make the terms such that no one gets a replacement battery. The idea is to make the terms as reasonable as possible, so that people who abuse the battery don't get a replacement battery, but people who use the battery as it's supposed to be used and ends up with a crappy battery gets a replacement battery.

Most people want to know what they are insured against, and not let it be up to the people footing the bill to determine. Would you go with an insurance company that said in it's terms: "Any and all insurance settlements will be reduced by an amount to be determined by the insurance company"? Sure, this amount could be 0.1% almost every time, but it opens for the insurance company to screw you.

AFAIK (I can check my paperwork when I get home) there is no language in the Roadster warranty about x% after y years or z miles. It says that if there's a defect that Tesla will replace or repair. To my knowledge Tesla has been willing to replace/repair batteries that were marginal as they are learning too. But again, AFAIK it's a judgement call on Tesla's part. My own personal speculation is that they can pull the logs of the car - the Roadster will always report the "weakest sheet" (there are 11 sheets in a Roadster pack). If one sheet stays the weakest for a very long time then it is bad and should be replaced under warranty. However if the weakest sheet changes over time then the capacity loss is gradual and is not a defect.

Thanks for checking it.

Yggdrasill · May 30, 2012

stopcrazypp said:
Any gradual loss in capacity for a lithium battery pack is expected behavior and can't be described as a defect. Therefore most car companies will not cover for that in a warranty. Only when something is unexpected, like the weak sheet strider described, will they possibly cover it. In many cases, it's up to the technician to decide (I know this is the case for the Volt).

Any gradual loss of capacity that is greater than expected can be describes as a defect.

If people expect 70% capacity after 8 years, with normal useage, and people only have 60%, they will consider that a defect. The way it is here, Nissan is probably obligated to replace the battery if it is at 60% after 8 years, because the expectations given to a customer in the advertizing is to a degree legally binding. Their only way out is if the terms in the warranty actually outlines reasonable assumptions for the 70% figure - and it simply does not.

I'm not sure if Tesla has advertized numbers for the expected capacity after X years, but if they have, they could also be obligated to replace batteries. (I don't believe Tesla has said anything about it.) But if Tesla doesn't say anything about it at some point, sales will probably suffer.

stopcrazypp said:
The closest thing you get in warranty coverage is that the battery has to provide enough *power* to meet the specs of the car as it was out of the factory. That means for the Leaf the pack has to be able to provide a bit more than 80kW (to run the motor at full bore, plus a bit more for accessories and heat losses). As the pack capacity falls, the max pack power falls in proportion (because max pack power = pack capacity * max C-rate). So if you get "lucky" it might fall under the power needed to run the car. However, most battery packs will be designed to have plenty of power left to spare.

Renault will replace a pack that falls below 75% capacity if you lease their pack (although it's kind of expected in terms of leasing), but I have not seen the actual written warranty. But I doubt an automaker that sells you a pack will specify a capacity in the warranty.

I think they are going to have to, if they want to sell to the mass market. People who have hundreds of thousands of dollars to spend on cars might be comfortable being a self-insurer, but people who can only just scrape together $40 000 for a car will not be comfortable with it.

VolkerP · May 30, 2012

Yggdrasill said:
Would you go with an insurance company that said in it's terms: "Any and all insurance settlements will be reduced by an amount to be determined by the insurance company"? Sure, this amount could be 0.1% almost every time, but it opens for the insurance company to screw you.

Did you ever encounter a major claim with an insurance company? :biggrin: It's exactly what they do: look into every detail of the event to see if they can reduce payment as much as possible by their legal artwork.
Perhaps what you propose is not a manufacturers warranty but a battery insurance? :tongue:

The points you listed as detrimental to the battery must be in the user manual anyway. Warranty or not, customers must be educated about that pricey asset named battery in their car.

Yggdrasill · May 31, 2012

VolkerP said:
Did you ever encounter a major claim with an insurance company? :biggrin: It's exactly what they do: look into every detail of the event to see if they can reduce payment as much as possible by their legal artwork.
Perhaps what you propose is not a manufacturers warranty but a battery insurance? :tongue:

The warranty is basically an insurance that the manufacturer of a product includes (hopefully at minimal cost) to entice customers.

And yes, I know insurance companies do what they can to reduce the payment, but that doesn't mean one should agree to terms that makes it trivial for an insurance company to reduce the payment to zero. In fact, that makes it all the more important to have a rock solid contract.

VolkerP said:
The points you listed as detrimental to the battery must be in the user manual anyway. Warranty or not, customers must be educated about that pricey asset named battery in their car.

I think the way it's done in many manuals is not good enough. Nissan says that fast charging is detrimental to the battery and shouldn't be done regularly. But how bad is it? What's considered normal useage which would result in 70% capacity after 8 years? Twice a day? Once a day? Twice a week? Once a week? Once a month? Once a year?

ElSupreme · May 31, 2012

We all know that Tesla has tested these batteries extensively. But one thing you can't duplicate is time. Tesla doesn't have enough data to provide a detailed battery warranty disclaimer. They are using degradation data from the cell manufacturer, that were developed in lab conditions on a small scale. And with temperature, and C rates and battery charge level when discharging and charging all being factors contributing to degradation it becomes impossible to really give a good picture.

There is also the problem with providing a 'worst case' scenario where it may be unacceptably low. If I saw a 'worst case' where Tesla only warranties the battery to 60% level after 100,000 miles I would be dissuaded from purchasing the vehicle. Where that may only be a fringe case that 1-2% (or less) of the population would experience. And most people would see about 85% battery level after 100,000 miles.

With a warranty you see what is covered, and hope that if it breaks the company providing the warranty doesn't screw you. That is pretty much the way of things.

daniel · May 31, 2012

The root problem, as ELSupreme says, is lack of sufficient real-world data. When manufacturers refuse to provide warranties specifying how much loss of capacity constitutes a defect, what they are really saying (and it would be nice if they said it outright, though perhaps that would hurt sales) is: We don't know how long these batteries will last. They are just too new. I think that if your Leaf battery declined "gradually" to 5% in the first week, Nissan would replace it. These things will be a judgement call, and any manufacturer will rule reasonably in the extreme cases. But in the cases where they can reasonably argue that the loss of capacity was caused by improper treatment (lots of use of high-power charging, or frequent charging to 100% or discharging to near zero) they'll claim it's your fault.

And because the technology is so new, and there's no long-term data, they intentionally keep terms like "frequently" vague, for their own protection.

Bottom line: Do not buy an electric car yet if you cannot accept the risk inherent in a new and untested technology. Do not buy an electric car yet if an out-of-warranty battery replacement in 4 or 5 years would cost more than you can afford. And do not buy an electric car yet if your driving needs would require you to charge to 100% and discharge to near zero on a daily basis and you cannot afford the battery replacement. If this is you, wait five years or 8 years, until there is a statistical history from which to judge battery longevity. I know a man who canceled his Leaf order and bought a plug-in Prius instead for exactly this reason. He decided he did not trust the battery from a company unwilling to provide a concise warranty on battery life.

FWIW, Tesla offered Roadster owners a battery replacement contract at the time of purchase. Offer was good for 90 days after purchase IIRC. $12,000 today gets you a replacement battery in seven years. Not a warranty. A pre-purchase. You pay today, you get the replacement in 7 years. And there was a pro-rated system if you wanted the battery a few years sooner or later. I did not buy it, because I expect my pack to last far longer than that. It's a chance I was willing to take. I'd have been willing to take a chance on the Leaf pack as well, though the Roadster, with its bigger pack, has lots more buffer.

In a decade, when the stats are in, manufacturers might offer the kind of warranty you are asking for.

VolkerP · May 31, 2012

daniel said:
The root problem is lack of sufficient real-world data. When manufacturers refuse to provide warranties specifying how much loss of capacity constitutes a defect, what they are really saying (and it would be nice if they said it outright, though perhaps that would hurt sales) is: We don't know how long these batteries will last. They are just too new.

As Tesla continues to use the second-to-latest cells in its battery packs, they will always have this problem. They cannot rely on 10 year old, well tested cells because the competition would outperform them with state-of-the-art battery chemistry. There is a sweet spot between running bleeding edge (with higher potential of warranty hassles) and lagging behind (with low risk, but low performance) and I am sure Tesla is spending big efforts on continually adjusting their technology towards it. I mean, if a manufacturer expects x% of all packs degrade below warranty threshold without detrimental treatment, he can swallow the warranty replacement cost by raising the initial cost by x%. Choose x wisely.

stopcrazypp · May 31, 2012

Yggdrasill said:
Any gradual loss of capacity that is greater than expected can be describes as a defect.

If people expect 70% capacity after 8 years, with normal useage, and people only have 60%, they will consider that a defect.

Warranties are not about what the "people" expect. It's what the manufacturer expects and is willing to cover. And the problem is there's a huge variance depending on the battery cell; plus none of the cells being sold right now have been tested for 8 or 10 years (as they are warrantied). Calendar life testing can't be accelerated unfortunately (without a time machine).

So the manufacturer itself can't say what kind of life to expect from the cell. Plus the life will vary significantly with the way the pack is used (60% capacity is possible after 8 years or even shorter depending on how you use it, that's not a defect then!). Even with the formula you suggested (which most people won't be able to comprehend), there's no one out there that can tell you if it's accurate. So the only thing manufacturers can say for sure is that "gradual loss" is expected behavior and it's up to the descretion of the technician if a battery needs to be replaced.

There's also the PR problem where if they are conservative, they push away potential customers. If they are optimistic, they risk dealing with a warranty claim nightmare 8-10 years down the road. I don't expect manufacturers to put a hard capacity number in the warranty for this reason.

Like daniel suggest, what you want seems to fall more under insurance (which is about what the consumer expects). Maybe something similar to the Roadster replacement battery. You pay extra to have a peace of mind.

Yggdrasill · May 31, 2012

stopcrazypp said:
Warranties are not about what the "people" expect. It's what the manufacturer expects and is willing to cover. And the problem is there's a huge variance depending on the battery cell; plus none of the cells being sold right now have been tested for 8 or 10 years (as they are warrantied). Calendar life testing can't be accelerated unfortunately (without a time machine).

Well, it is to an extent about what the people are expecting. At least here. When it comes to the Nissan Leaf, people are expecting at least 70% range after 5 years/100 000 km. This is due to information provided by Nissan, and as long as the warranty information is vague as to the conditions of this figure, that doubt goes in the favour of the consumer. Nissan is in all proability required to replace any battery packs with less than 70% capacity after 5 years/100 000 km. (A court case may be required to set it in stone by creating a precedent.)

stopcrazypp said:
So the manufacturer itself can't say what kind of life to expect from the cell. Plus the life will vary significantly with the way the pack is used (60% capacity is possible after 8 years or even shorter depending on how you use it, that's not a defect then!). Even with the formula you suggested (which most people won't be able to comprehend), there's no one out there that can tell you if it's accurate. So the only thing manufacturers can say for sure is that "gradual loss" is expected behavior and it's up to the descretion of the technician if a battery needs to be replaced.

There's also the PR problem where if they are conservative, they push away potential customers. If they are optimistic, they risk dealing with a warranty claim nightmare 8-10 years down the road. I don't expect manufacturers to put a hard capacity number in the warranty for this reason.

As I said earlier, it will be hard to penetrate the mass market if the manufacturers aren't willing to caugh up a warranty. It isn't exactly reassuring that a manufacturer isn't willing to put it into a contract that their product will still work a few years down the line. People are used to being able to buy a car with a warranty that ensures the car will still work a few years down the line.

I've tried to defend EVs when they catch flak over the vague/worthless battery warranties, but it isn't exactly easy. There won't be any improvement until manufacturers are willing to put a number on a piece of paper; a good number. The vague warranty terms in no way help EV adoption.

My best defence of Tesla thus far is that if a 85 kWh battery is at say 60% after 5 years/300 000 miles, and Tesla refuses a replacement, there's nothing preventing the owner from driving the car like it's stolen until the battery gives up, is defective by any standard, and has to replaced by Tesla. That strikes me as a pretty poor solution, for everyone.

stopcrazypp said:
Like daniel suggest, what you want seems to fall more under insurance (which is about what the consumer expects). Maybe something similar to the Roadster replacement battery. You pay extra to have a peace of mind.

Of course you have to pay extra for peace of mind, but this extra cost should be included in the purchase cost. For the Model S, I think peace of mind should come standard on a car that is supposed to be "the best sedan on the planet".

jerry33 · May 31, 2012

Yggdrasill said:
I think the way it's done in many manuals is not good enough. Nissan says that fast charging is detrimental to the battery and shouldn't be done regularly.

They've actually changed their tune on that and now say the manual is incorrect and that you can quick charge as often as you want without harm. However, I can't find the link where Ghosn said that--it could have been in a video interview. The older manual said:NISSAN recommends that quick charging not be performed more than once a day.

stopcrazypp · May 31, 2012

Yggdrasill said:
Well, it is to an extent about what the people are expecting. At least here. When it comes to the Nissan Leaf, people are expecting at least 70% range after 5 years/100 000 km. This is due to information provided by Nissan, and as long as the warranty information is vague as to the conditions of this figure, that doubt goes in the favour of the consumer. Nissan is in all proability required to replace any battery packs with less than 70% capacity after 5 years/100 000 km. (A court case may be required to set it in stone by creating a precedent.)

At most you can only sue them for false advertisement (and PR statements, or like in Nissan's case just spoken answers to the press may not even qualify as advertisement). Nissan will not be liable for anything not written in the warranty (which is why when PR talks about something, I actually read the written warranty instead to see what it really says). I think it's wishful thinking to think otherwise.

People are used to being able to buy a car with a warranty that ensures the car will still work a few years down the line.

Every battery warranty for EVs/PHEVs/HEVs ensures the car works properly (it will be able to be driven at max power with all accessories on by the end of the warranty period). There's no change there from any standard warranty. It does NOT cover capacity in any way. This is true of almost all battery warranties as far as I know (for cell phones, laptops, starter batteries, etc). They only cover capacity by proxy (meaning capacity falling enough to affect proper operation).

I've tried to defend EVs when they catch flak over the vague/worthless battery warranties, but it isn't exactly easy. There won't be any improvement until manufacturers are willing to put a number on a piece of paper; a good number. The vague warranty terms in no way help EV adoption.

They'll be willing to put a number when they are sure what is a "good number". It'll take a while to establish that for the various battery cells they are using (some of them were still in the lab a couple of years ago, much less in cell form and testing already). Here's what Tesla has to say about the Model S battery:
" How many years will the battery last?
Based on testing, Tesla expects the battery to retain approximately 70% of its initial capacity after seven years or 100,000 miles."
http://www.teslamotors.com/en_CA/models/faq
If they put that in the warranty, they'll be the first ones to cover capacity in a warranty. Of course "approximately" probably will have to change for a solid warranty. I think for the most part manufacturers will put out vague statements like that in the meantime.

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