Standard Warranty Revealed

[stopcrazypp]

I investigated the issue a bit further, and here, at least, the following producers hava a warrantied minimum capacity:

Citroen C-Zero: A minimum of 80% at 5 years / 50,000 km.
Mitsubishi i-MiEV: A minimum of 80% at 5 years/ 100,000 km.
Buddy, lead-acid: A minimum of 60% at 2 years/ 20,000 km.
Buddy, NiMH: A minimum of 80% at 10 years/ 100,000 km.
Tazzari Zero: A minimum of 70% at 5 years/ 50,000 km.
Ford/Azure Transit: A minimum of 80% at 5 years/ 100,000 km.
Enviro Bil, MIA Electric: A minimum of 80% at 5 years/ 80,000 km.
eCar Norge/Classic Electrics ecar 500 EV: A minimum of 80% at 5 years/ 100,000 km.

If these companies can do it, why can't Tesla?

Links to the written warranty please or some sources for this (can't seem to find them just by googling, I find only your post when I do).

The 5 year/62.5k mile warranty for the Euro market iMIEV (this includes the UK and Norway, see page 8) specifically does NOT cover capacity (page 2):

Normal wear and tear on Traction Battery is not covered by this warranty.

http://www.mitsubishi-cars.co.uk/images/faq/WarrantyTermsandConditionsi-MiEV.pdf

The 8year/100k mile US market iMIEV battery warranty specifically does NOT cover capacity (see page 8):

Gradual capacity loss of the Main Drive Lithium-ion Battery based on time and usage is NOT covered under this warranty.

http://myimiev.com/forum/viewtopic.php?f=5&t=15&view=previous

The Norway and UK battery/powertrain 5 year /100k km warranty for the Transit Connect Electric makes no mention of coverage of battery capacity (only defects):
http://www.transitconnectelectric.net/pdf/dealer_admin/2011_LPW_Norway.pdf
http://www.transitconnectelectric.net/pdf/dealer_admin/2011_LPW_UK.pdf
The 5 year/ 60k mile warranty on the US spec Transit Connect Electric is similar:
http://azdtec.com/dealer/support/TCE/PDF/107388-A%20(English)ReadOrder.pdf

And like I said, the worse case degradation for Tesla's cells to 70% is 3-5 year 40k/60k/80k mile. They numbers you posted seem to correspond well to my prediction.
http://www.teslamotorsclub.com/show...ranty-Revealed?p=171114&viewfull=1#post171114

Like jerry33 said, here in the US, if your battery warranty was only 63k miles, you would be laughed at (I'm assuming the cars you linked also have a defect warranty that's longer than that). My question is how receptive would people be if Tesla provided a 3-5 year 40k/60k/80k mile warranty to 70% degradation? Would that address their concern or would it cause more concern?

 

[jerry33]

My question is how receptive would people be if Tesla provided a 3-5 year 40k/60k/80k mile warranty to 70% degradation? Would that address their concern or would it cause more concern?

Based on the comments I see about cars with large batteries on non-automotive sites (the automotive sites tend to be polarized), it appears that almost everyone who hasn't had experience with large battery cars believes that the battery will fail one foot or one minute after the warranty expires. Because people tend to take the lowest case, the comments will be "You have to purchase a new battery every 40,000 miles if you buy one of those things." if you had a 40/60/80 mile warranty. It is going to take a lot to convince the average person that the battery is no more likely to fail soon after the warranty expires than is the engine in an old fashioned car.

When I tell people I have over 135,000 miles on my Prius their first question is "How many batteries have you gone through?". They are surprised when I tell then I am on the original, that the batteries last for a very long time, and that I don't expect to replace the battery for a long time to come.

 

[J in MN]

From Tesla's latest 10-Q filing:

For example, we currently expect that our battery pack for the Tesla Roadster will retain approximately 60-65% of its ability to hold its initial charge after approximately 100,000 miles or seven years, which will result in a decrease to the vehicle’s initial range.

 

[stopcrazypp]

it appears that almost everyone who hasn't had experience with large battery cars believes that the battery will fail one foot or one minute after the warranty expires. Because people tend to take the lowest case, the comments will be "You have to purchase a new battery every 40,000 miles if you buy one of those things."

That's the concern I had too when I talked about the disadvantage in advertising (although I didn't go into specifics).

A defect warranty allows Tesla (and other manufacturers) to warranty for the average expected life of the battery without too much liability (so they can provide the now industry standard 8 year/100k mile battery warranty period). You can't do the same thing with a capacity warranty: you have to provide one that only warrants for the worse case if you want to avoid having to cover many batteries. If you provide an average case capacity warranty and assuming the typical bell curve distribution, Tesla may have to replace as much as half of the batteries they are covering and that's clearly unacceptable. So either they provide a much shorter capacity warranty or provide a longer one and charge you extra for the liability (it's insurance basically). The $12k Roadster battery replacement option is an example of the latter.

 

[Discoducky]

Here's my concern, if I get the 85kWh and drive say 200K miles in 8 years, how much initial % charge can I expect under warranty? This is a very likely scenario for my family. If after 100K it's 65%, what does the graph look like for more miles? Is it linear? like 30% after 200K?

I'm worried that the warranty will not state the minimum level of initial charge % with a given amount of miles. I'd really need to see some sort of graph that shows the expected degradation rate per the verbiage of the warranty.

 

[JRP3]

200K miles at say around 200 miles per charge is 1000 cycles at around 65% DOD per cycle of a 300 mile pack. Disregarding temperature variables and driving style I'd say that's fairly conservative use and the pack should still be above 70%. As I've mentioned previously the graphs I've seen for the new Panasonic cells show capacity loss flattening out around 70% of original capacity.

 

[stopcrazypp]

Here's my concern, if I get the 85kWh and drive say 200K miles in 8 years, how much initial % charge can I expect under warranty? This is a very likely scenario for my family. If after 100K it's 65%, what does the graph look like for more miles? Is it linear? like 30% after 200K?

I'm worried that the warranty will not state the minimum level of initial charge % with a given amount of miles. I'd really need to see some sort of graph that shows the expected degradation rate per the verbiage of the warranty.

No need to guess when Panasonic already posted the actual cycle testing data. I've posted a handy chart here a year ago (the cells used by the 85kWh pack is the NCR18650A):
http://www.teslamotorsclub.com/show...or-Model-S/page2?p=61317&viewfull=1#post61317

Might as well show it again:

Basically I have Model S (ideal) miles to the left. The cycle number refers to full cycles, so you can just multiply that by 300 miles to get the miles at that point (example: at the end, it's 500 cycles * 300mi/cycle = 150k miles at that point).
In terms of the loss in percent:
0-300 cycles: lose ~7.8%/23.4mi per 100 cycles/30k miles
300-500 cycles: lose ~1.35%/4.05mi per 100 cycles/30k miles

To answer your question specifically about 200k miles, if I extrapolate graph to 200k miles/666.7 cycles using the degradation rate from 300-500 cycles, I get 2172mah = 217.2 miles =72.4% (assuming the car comes delivered at 300 miles = 3000mah and not at the 3100 mah that degrades to 3000 mah in just 5 cycles in the graph; if you assume 3100mah is the full capacity then that works out to exactly 70% at 200k miles/666.7 cycles). You can see clearly why Tesla has no qualms about offering an unlimited mile warranty on the 85kWh pack.

I haven't been able to find real data on calendar life degradation (edit: found some, see below), but the number according to wikipedia is a laptop cell stored at 40-60% at room temperature loses ~4% in the first year. Assuming that's linear, in 8 years, you would have lost ~32% or have ~68% capacity left.

I found some calendar life testing. It is a 2010 report on 8 year old Sony 18650HC cells from 2002 (it's for a satellite battery). Page 19 shows the degradation results of a test where the cells are cycled with a 75% SOC window for 45 days and each cell kept at 4V for 138 days (the "season" they mention is a solstice season so that means half a year). Basically between season 1-2, it loses 3.5% per season and levels off to 0.5% per season. Ignore the "gain" in capacity in season 7-8 (that's because they raised the peak charge voltage).
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA515369
Using this model of 7% in the first year and 1% loss per year thereafter, in 8 years you lose 14% and have 86% left in capacity.

 

[Dave EV]

Links to the written warranty please or some sources for this (can't seem to find them just by googling, I find only your post when I do).

The only plug-in I've found in the USA that appears to warrant battery capacity is the 8-year 100k mile warranty on the Chevrolet Volt.

http://www.chevrolet.com/content/dam/Chevrolet/northamerica/usa/nscwebsite/en/Home/Ownership/Manuals%20and%20Videos/02_pdf/2011_chevrolet_volt_warranty.pdf

See page 14:

Propulsion Battery Warranty Policy
Like all batteries, the amount of energy that the high voltage “propulsion” battery can store will decrease with time and miles driven. Depending on use, the battery may degrade as little as 10% to as much as 30% of capacity over the warranty period. A dealer service technician will determine if the battery energy capacity (kWh storage) is within the proper limit, given the age and mileage of the vehicle. Typical tests can take up to 24 hours.

It seems to be very difficult to void this warranty. GM has gone out of their way to make the way the car cares for it's battery fairly bullet-proof.

 

[brianman]

The cycle number refers to full cycles, so you can just multiply that by 300 miles to get the miles at that point (example: at the end, it's 500 cycles * 300mi/cycle = 150k miles at that point).

I'm confused by this.

I would expect cycles to be relative to pack capacity at the time. For example, at cycle number 200 the mileage is around 250. As such, for cycle 201 a full charge is near 250. Consequently, you can't just multiply the original range (300) by the cycle count (500) but instead have to add up the individual multiplications of each cycle by its battery range for that cycle. Right?

 

[Dave EV]

One cannot simply take off-the-shelf cycle capacity loss chart and apply it to use in a car. It's comparing apples to oranges.

Primary reason - 2 half-cycles does not equal 1 full cycle in terms of battery life. In addition, keeping the battery pack out of the top and bottom of available capacity results in very large gains in durability and cycle life.

So taking the referenced data sheet and claiming that if you drive 300 miles at 55 mph every day for a year will end will result in your pack holding less than 80% of it's original capacity is simply not true.

Unless you've actually done exactly that with the actual cells used in the car - you really can't say.

 

[stopcrazypp]

I'm confused by this.

I would expect cycles to be relative to pack capacity at the time. For example, at cycle number 200 the mileage is around 250. As such, for cycle 201 a full charge is near 250. Consequently, you can't just multiply the original range (300) by the cycle count (500) but instead have to add up the individual multiplications of each cycle by its battery range for that cycle. Right?

Technically you are right, I just use the full range for easy math (esp. for the extrapolation). To get the accurate number you are talking about, you would have to integrate (get the area under the graph) and that's a lot of work without a spreadsheet and only a rough graph.

 

[stopcrazypp]

ba

The only plug-in I've found in the USA that appears to warrant battery capacity is the 8-year 100k mile warranty on the Chevrolet Volt.

http://www.chevrolet.com/content/da...ideos/02_pdf/2011_chevrolet_volt_warranty.pdf

It seems to be very difficult to void this warranty. GM has gone out of their way to make the way the car cares for it's battery fairly bullet-proof.

I've already read that warranty and I don't interpret it as a "minimum 70%" warranty like people are asking for. It's certainly better than a warranty that explicitly doesn't cover battery capacity, but that warranty essentially is saying it's up to the technician to determine if your battery capacity is appropriate for its age and mileage and it's not setting a hard limit. And given that the Volt never hits 100% SOC (but rather uses a ~60-70% SOC window, in the range around 30% SOC and 80% SOC), it's very hard for a regular consumer to detect the degradation of the battery (unlike with the Leaf where you explicitly lose bars as your battery capacity diminishes, in the Roadster you lose ideal miles). Given those factors, I can see why GM saw it as an acceptable risk to write that in the warranty.

In the context of the whole Nissan Leaf battery controversy (where some people have lost 3 bars of battery capacity, equivalent to a 25% loss in capacity), GM wouldn't have to replace any batteries under that warranty (they just need to say the loss is "normal" for the pack at that age/mileage, like Nissan's techs have been saying for the Leaf packs).

One cannot simply take off-the-shelf cycle capacity loss chart and apply it to use in a car. It's comparing apples to oranges.

Primary reason - 2 half-cycles does not equal 1 full cycle in terms of battery life. In addition, keeping the battery pack out of the top and bottom of available capacity results in very large gains in durability and cycle life.

So taking the referenced data sheet and claiming that if you drive 300 miles at 55 mph every day for a year will end will result in your pack holding less than 80% of it's original capacity is simply not true.

Unless you've actually done exactly that with the actual cells used in the car - you really can't say.

I certainly know that. But that actual data is only known by Tesla and it's unlikely to be posted publicly (for competitive reasons). But you can use the cycle life chart of the cell as a fairly accurate conservative estimate (and that was my intention). Basically since it's a full cycling at 0.5C charge and 1C discharge, that's like using the car in a 100 SOC window using 2 hour charging and discharging at a power of 1C average (40kW for 40kWh pack, 60kW for 60kWh pack, 85kW for 85kWh pack). Essentially, almost all cars will not see that kind of cycling (they will see partial cycling with slower charging and discharge), so this is a conservative measure (I should add that supercharging and racing is the exception).

 

[Yggdrasill]

Umm, the highest number there is 100,000 km (63,000 miles). The car is still practically new at that point (or should be). Not much of a warranty risk for the vehicle manufacturer. If Tesla put out warranty numbers like that they would be laughed at. 63,000 miles is not even four years' driving unless you're using it as a weekend-only car.

A 80% at 5 years/100 000 km warranty for a 16 kWh battery would be about the same as a 5 year/531,000 km warranty for an 85 kWh battery pack. For the total mileage on a battery before replacement, you need to adjust for capacity (range per cycle, basically). This isn't completely rright, of couse, as the i-MiEV is a more efficient car and can travel further with less impact on the battery. Going by the EPA range, the Mode S uses 200 Wh/km, while the i-MiEV uses 160 Wh/km. That means that a 85 kWh pack of i-MiEV li-ion cells placed in a Model S should have a warranty of 5 years/425,000 km to be identical to the battery warranty of the i-MiEV. (The power would also need to be no more than 250 kW, and charging could occur at no more than 239 kW. To be completely equivalent, that is.)

Of course, I believe that the i-MiEV uses more durable cells of a different chemistry, so Tesla probably couldn't warranty quite as much as the i-MiEV, but I'd hope 70% (instead of 80%) at 200,000 miles would be doable, at least.

 

[Yggdrasill]

Links to the written warranty please or some sources for this (can't seem to find them just by googling, I find only your post when I do).

The 5 year/62.5k mile warranty for the Euro market iMIEV (this includes the UK and Norway, see page 8) specifically does NOT cover capacity (page 2):
http://www.mitsubishi-cars.co.uk/images/faq/WarrantyTermsandConditionsi-MiEV.pdf

The 8year/100k mile US market iMIEV battery warranty specifically does NOT cover capacity (see page 8):
http://myimiev.com/forum/viewtopic.php?f=5&t=15&view=previous

The Norway and UK battery/powertrain 5 year /100k km warranty for the Transit Connect Electric makes no mention of coverage of battery capacity (only defects):
http://www.transitconnectelectric.net/pdf/dealer_admin/2011_LPW_Norway.pdf
http://www.transitconnectelectric.net/pdf/dealer_admin/2011_LPW_UK.pdf
The 5 year/ 60k mile warranty on the US spec Transit Connect Electric is similar:
http://azdtec.com/dealer/support/TCE/PDF/107388-A%20(English)ReadOrder.pdf

And like I said, the worse case degradation for Tesla's cells to 70% is 3-5 year 40k/60k/80k mile. They numbers you posted seem to correspond well to my prediction.
http://www.teslamotorsclub.com/show...ranty-Revealed?p=171114&viewfull=1#post171114

Like jerry33 said, here in the US, if your battery warranty was only 63k miles, you would be laughed at (I'm assuming the cars you linked also have a defect warranty that's longer than that). My question is how receptive would people be if Tesla provided a 3-5 year 40k/60k/80k mile warranty to 70% degradation? Would that address their concern or would it cause more concern?

I'm going by the overview worked out by our electric car association, NAF (the biggest car association here) and a consumer agency. Overview (It's changed since last time - now Citroen is listed with a 120,000 km warranty.)

Looking around a bit I find specific references to a press release in january. I'll try to find it.

Found it.

 

[Discoducky]

To answer your question specifically about 200k miles, if I extrapolate graph to 200k miles/666.7 cycles using the degradation rate from 300-500 cycles, I get 2172mah = 217.2 miles =72.4%

Using this model of 7% in the first year and 1% loss per year thereafter, in 8 years you lose 14% and have 86% left in capacity.

So, if I'm reading right, then the 85kWh after 200K miles and 8 years would lose about 40% capacity?

 

[stopcrazypp]

So, if I'm reading right, then the 85kWh after 200K miles and 8 years would lose about 40% capacity?

No, it doesn't work that way; it's not directly additive. It's roughly "whichever comes first" just like the warranty is. Basically it's a race between the cycle life and the calendar life. You take the worse number, which is the 72.4% for cycling in this case.

Evidence of this is the way NREL models battery life (which fits well with the empirical data they have), they also take the minimum relative capacity (page 18):
http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/45048.pdf

 

[stopcrazypp]

I'm going by the overview worked out by our electric car association, NAF (the biggest car association here) and a consumer agency. Overview (It's changed since last time - now Citroen is listed with a 120,000 km warranty.)

Looking around a bit I find specific references to a press release in january. I'll try to find it.

Found it.

Either Mitsubishi is doing false advertising (my link to the European warranty for the iMIEV explicitly doesn't cover capacity), or my best guess is Norway just had a recently had a law that required them to amend their warranty to cover capacity and Mitsubishi (and Azure) have not updated their warranty to reflect that. Anyways, the situation there is unusual in that all the written battery warranties I can find don't cover capacity. I also browsed the website of the other cars you mentioned and at least on their English language sites they don't mention any coverage/guarantee for capacity.

 

[Yggdrasill]

Either Mitsubishi is doing false advertising (my link to the European warranty for the iMIEV explicitly doesn't cover capacity), or Norway just had a recently had a law that required them to amend their warranty to cover capacity and Mitsubishi (and Azure) have not updated their warranty to reflect that. Anyways, the situation there is unusual in that all the written battery warranties I can find don't cover capacity. I also browsed the website of the other cars you mentioned and at least on their English language sites they don't mention any coverage/guarantee for capacity.

Norway may be odd in that our consumer rights are protected quite well by law. We have consumer rights that no contract can take away (just as no contract you sign can allow anyone to assault you or kill you in the US), and among these are a 5 year retur/repair-policy for goods intended to last substantially longer than 3 years. This includes cell phones, for instance. If a cell phone breaks after 4 years, through no fault of your own, you can demand a repair or refund. What is the general guideline for if you get a repair or refund, is what it would be reasonable to expect, given the advertizing and other information about the product in question.

This puts Mitsubishi, Nissan and the rest at a bit of a disadvantage, as they've pushed the 80% capacity after 5 years, 70% after 8 years line quite hard. This means that if you take them to court, you have a very good case, if the battery capacity is less than 70%. Warranty or no warranty. So, as they find themselves in this situation, they might as well make the best of it, avoid costly legal battles (that they would lose), and simply include the battery capacity limit in the warranties. Nissan hasn't gone to that step yet, but they will be forced to soon enough.

This could affect Tesla in that what is more-or-less becoming an industry standard is the standard to which Tesla will be held, and especially the unlimited mileage on the 85 kWh battery pack is problematic from the legal standpoint. The courts could very well determine that this means that the battery pack will have a minimum of 70% for unlimited miles/5 years. The solution for Tesla is simple - make a reasonable warranty for the battery pack, which includes a minimum capacity and fair use guidelines. Doubt and uncertainty does not work in Tesla's favour.

(Actually, I would be very surprised if the warranty here would be for unlimited miles, but we'll see. If the warranty is no good, maybe I'll wait a few years before buying a Tesla.)