Tesla Motors current and future battery degradation warranty...

[CatB]

To JohnQ - is that true? I ask because I was at 90% drove 170 miles (range said 30 left) and only 48 kwh were "used" - I was told that that kwh number doesn't include power used for AC and other accessories.

Does anybody remember hearing about a battery replacement program? For some reason I remember you could prepurchase a battery at year 10 for $12k, or $11k at year 11...

 

[JohnQ]

To JohnQ - is that true? I ask because I was at 90% drove 170 miles (range said 30 left) and only 48 kwh were "used" - I was told that that kwh number doesn't include power used for AC and other accessories.

Does anybody remember hearing about a battery replacement program? For some reason I remember you could prepurchase a battery at year 10 for $12k, or $11k at year 11...

To my knowledge, and I'll admit it's imperfect, the trip meter mileage shows total energy usage while the car is on from your last charge including accessories. So, if you let it sit after a full charge and the fans are running to help cool the battery then that would not be included but while driving, or "idling" in traffic or at a stop light, that would be included.

 

[JRP3]

The power for the 12V system and all accessories comes from the main pack, so all of that is included in kwh's used.

 

[dhanson865]

Time will also solve much of this. If the packs behave the way I expect there will be plenty of examples of high mileage cars 2-3 years from now with minimal capacity loss and no examples of unexpectedly high capacity loss.

The problem with putting a specific number in a warranty is that number will have to be lower than the average expected loss, which will make pack durability look worse than it actually is.

You could easily back it up with data if you are willing to do so. Something like:

After reviewing data from all our Model S on the road we have noticed a trend that converges on 15% battery loss per 100,000 miles traveled. This is clearly better than the warranty which we are now announcing but expect few to use. If you are one of the few that for any reason get to 30% battery loss in the first 100,000 miles please notify your nearest service center. We will diagnose the issue and remedy it by a method of our choosing that may include replacing some or all of:

BMS
Battery Pack
Inverter
Cooling system
or any other part that may have caused the issue.

Obviously I don't have access to real numbers and I don't know if I even named the parts correctly that I'd want in the announcement (it needs to cover cases where perceived loss due to instrumentation errors occur and shouldn't force the company to replace the most expensive part if range can be restored without doing so).

I don't see any reason they can't let people know there is an expected loss that is different than the limit that would trigger free repairs.

 

[robby]

As a hopeful-to-be Tesla owner, I can attest to the value it'd provide if Tesla would be more clear about what degradation should be expected and covered by warranty.

Most of our driving is 165-mile trips between Boston and the White Mountains. For most of the year this will be no problem, but if I'm to expect 70-80% battery loss, the winters will no longer be doable in one trip. That's not to say those numbers are unreasonable or unworkable, but they're numbers I'd like to know before making the purchase.

 

[yobigd20]

Actually it's not that hard if you have access to the BMS logs, which Tesla does. Imbalanced or weak cells will show up quite clearly.



Page 20 http://www.embedded-world.eu/fileadmin/user_upload/pdf/batterie2011/Sonnemann_Panasonic.pdf
80% to around 1000 full cycles, discharging to 2.5V, which never happens in a car, 75% at 2000 cycles, and 70% isn't reached until over 2600 cycles. 1000 cycles on a 260 mile pack is over 200,000 miles even taking capacity loss into consideration.

You have to remember that two 50% cycles does not equal one 100% cycle. Similarly, four 25% cycles does not equal two 50% cycles, and so on. The smaller the cycles for the equal total amount, the better. So 500 100% cycles (~132k miles driven) might degrade the battery to 80% but 2000 25% cycles (also ~132k miles driven) might only degrade the battery to 95% (making that number up but only to illustrate the point). In the model S we will never do a full cycle because of the reserve amounts that we never touch. That alone drastically prolongs the the capacity of the battery over those 100% cycle specifications. It's also been proven that the amount of time spent at high cell temperatures plays a big role in the degradation process. However, Tesla's thermal management system keeps the temps stable within a safe range even when fast charging. That also seriously reduces battery degradation. I would be very very surprised to see any significant degradation in the model S's battery packs regardless of age and mileage. There will be some, but definitely on an totally different scale and less magnitude than those OEM Panasonic specs. Most if not all of the variation we see today across similar model S is due to differences in the battery pack balances and capacity estimation calculations - not from any actual degradation happening.

 

[Chickenlittle]

As a hopeful-to-be Tesla owner, I can attest to the value it'd provide if Tesla would be more clear about what degradation should be expected and covered by warranty.

Most of our driving is 165-mile trips between Boston and the White Mountains. For most of the year this will be no problem, but if I'm to expect 70-80% battery loss, the winters will no longer be doable in one trip. That's not to say those numbers are unreasonable or unworkable, but they're numbers I'd like to know before making the purchase.

What started this was a roadster owner who, despite the system and manual warning not to frequently range charge did so. Does not apply to model s. For model s no such warnings, different battery chemistry, different battery management. 1/3 to 1/2 of his miles were range charged and again a different car and battery. I was concerned some would confuse roadster with model s

 

[woof]

But we do have a way to measure actual capacity with a reasonable degree of accuracy. If I do a 100% charge, then drive down to or around 0 miles

Not sure with about the Roadster, but with the 3 EV's I've owned "0" doesn't mean "no power left". You really have to drive it till it won't move anymore. Even then that doesn't really drain the battery because of various anti-bricking safeguards. And there are reports that for the Model S the "0" point (and probably the "won't move point") has changed depending on firmware version.

So I get your point, but in practice it turns out to be very difficult to do.

 

[robby]

What started this was a roadster owner who, despite the system and manual warning not to frequently range charge did so. Does not apply to model s. For model s no such warnings, different battery chemistry, different battery management. 1/3 to 1/2 of his miles were range charged and again a different car and battery. I was concerned some would confuse roadster with model s

Yeah, I understand and the context here isn't lost on me. But I do think Tesla should clarify how much or how little degradation is expected. When Tesla increased its warranty, Elon said "If we truly believe that electric motors are fundamentally more reliable than gasoline engines, with far fewer moving parts and no oily residue or combustion byproducts to gum up the works, then our warranty policy should reflect that."

Since Tesla specifically excluded battery degradation, it's reasonable to ask what those expectations are and, if they can provide an answer with confidence, why it isn't similarly covered.

 

[JRP3]

You have to remember that two 50% cycles does not equal one 100% cycle.

Thanks for the tip :wink:

Similarly, four 25% cycles does not equal two 50% cycles, and so on. The smaller the cycles for the equal total amount, the better. So 500 100% cycles (~132k miles driven) might degrade the battery to 80%...

No it probably won't, since the test protocol I linked and referenced took the cells to a lower SOC than Tesla allows. I consider the figures I used from the testing to be the worst case scenario, since as you state actual use will be more shallow cycling, which increases pack life.

 

[anticitizen13.7]

Yeah, I understand and the context here isn't lost on me. But I do think Tesla should clarify how much or how little degradation is expected. When Tesla increased its warranty, Elon said "If we truly believe that electric motors are fundamentally more reliable than gasoline engines, with far fewer moving parts and no oily residue or combustion byproducts to gum up the works, then our warranty policy should reflect that."

Since Tesla specifically excluded battery degradation, it's reasonable to ask what those expectations are and, if they can provide an answer with confidence, why it isn't similarly covered.

I know that the battery degradation issue is a topic of interest for mobile phone users. Does anyone know what the standard is for replacement of a faltering iPhone battery when the iPhone is still within its warranty period? I wonder if the Apple approach might provide some guidance for Tesla.

 

[kbeckley]

If I was Tesla (and I certainly am not) as long I am supply limited I would not put any specifics around degradation %. It seems clear to me from all the reading I have done on Lithium battery chemistry that you only really know exactly how long a battery will last if you actually run it until it dies. However all the research points to very specific traps to avoid (the big one being heat at 100% charge for example). It so happens that Tesla is involved in the most diabolically massive Li-ion battery experiment of all time. On a daily basis they will be getting data that others can only dream of (which is one reason I don't think releasing their patents is not going to hurt them). So by the time the Gen 3 comes around if they feel they need to they can put, with confidence, specific numbers around what % degradation vs distance driven is "normal'.

On another note I wonder how many model S owners know what their day 1 baseline range was. I don't. Add in software updates that have seemed to tweak what 100% is without your baseline what is 80% anyway. I would seem to me that you would have to sit with your delivery specialist and agree then document "when I got the car full range was X km". Or they would have to say any new car starts with a baseline of, say 410km (yours may be better).

Anyway I think they should just keep on gathering their data and when needed to assuage future more-nervous buyers they will have a ton more confidence in stating specifics.

Finally I think that in almost 2 years and 50,000km I have lost little if any range. My driving: ~65km daily with the longer drives on most weekends.

 

[Matias]

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.)

.

Actually many ICE cars do better after 60 000km than brand new. When I read car magazines, at least 0-100 km/h values are better after 60 000km than when the same car was new. Probably friction reduces after break in.

 

[Tasdevil]

I think tesla is waiting for the gigafactory before committing to battery warrenty/replacement/cost etc.
I think elon will deal with this before he steps down

 

[David_Cary]

If I was Tesla (and I certainly am not) as long I am supply limited I would not put any specifics around degradation %. It seems clear to me from all the reading I have done on Lithium battery chemistry that you only really know exactly how long a battery will last if you actually run it until it dies. However all the research points to very specific traps to avoid (the big one being heat at 100% charge for example). It so happens that Tesla is involved in the most diabolically massive Li-ion battery experiment of all time. On a daily basis they will be getting data that others can only dream of (which is one reason I don't think releasing their patents is not going to hurt them). So by the time the Gen 3 comes around if they feel they need to they can put, with confidence, specific numbers around what % degradation vs distance driven is "normal'.

On another note I wonder how many model S owners know what their day 1 baseline range was. I don't. Add in software updates that have seemed to tweak what 100% is without your baseline what is 80% anyway. I would seem to me that you would have to sit with your delivery specialist and agree then document "when I got the car full range was X km". Or they would have to say any new car starts with a baseline of, say 410km (yours may be better).

Anyway I think they should just keep on gathering their data and when needed to assuage future more-nervous buyers they will have a ton more confidence in stating specifics.

Finally I think that in almost 2 years and 50,000km I have lost little if any range. My driving: ~65km daily with the longer drives on most weekends.

Of Course Nissan actually has more batteries and more numbers on degradation. They presumably monitor all the batteries and have tons of data. So Tesla's is not the most diabolically massive battery experiment - Nissan still has about 2x as many cars sold. And right now, Tesla is not selling more per month and possibly won't catch up for awhile.

Battery degradation warranties are a good idea. A stated minimum (70% at 8 years/100k is fine) would work. It could then be supplemented with 10% worse than average degradation. Base minimum could justify a new battery, the 10% worse could mean prorated replacement.

There is no prepaid option for $12k as some people seem to think. It was floated as an option but never became possible.

 

[robby]

I know that the battery degradation issue is a topic of interest for mobile phone users. Does anyone know what the standard is for replacement of a faltering iPhone battery when the iPhone is still within its warranty period? I wonder if the Apple approach might provide some guidance for Tesla.

Apple warranties 80% capacity after 500 complete cycles (not any 500 charges). It's 1000 cycles for laptops.

Apple - Batteries - Replacement and Recycling

 

[scaesare]

Of Course Nissan actually has more batteries and more numbers on degradation. They presumably monitor all the batteries and have tons of data. So Tesla's is not the most diabolically massive battery experiment - Nissan still has about 2x as many cars sold. And right now, Tesla is not selling more per month and possibly won't catch up for awhile.

With 7000+ batteries per pack, versus Nissan's 192 (a 37x difference), Tesla's battery numbers already dwarf Nissan's.

If you want to say number of "packs", then you are likely correct. But I suspect that pack failures/degradation are diagnosed down to the cell level (even if repaired at the module or pack level), so Tesla already has some significant data that will help them understand what's going on.

 

[ecarfan]

In another thread about Kevin Sharpe's dispute with Tesla over how much battery capacity loss is acceptable before warranty coverage kicks in, @Lump posted this text from the Kia Soul EV battery warranty indicating that up to 30% capacity loss is allowed before a Kia will repair/replace the battery under warranty:

--------------------------------------------------
* Lithium-Ion Polymer Battery Capacity Coverage

The Lithium-Ion Polymer Battery (“EV Battery”) Capacity warranty coverage period is 10 years or 100,000 miles from the Date of First Service, whichever comes first, for capacity loss below 70% of the original battery capacity. This warranty covers repairs needed to return battery capacity to 70% of original battery capacity. If possible, the EV battery components will be repaired or replaced,and the original EV Battery will be returned to the vehicle. If necessary, the EV Battery will be replaced with either a new or remanufactured Lithium-Ion Polymer Battery. Any repair or replacement made under this Lithium-Ion PolymerBattery Capacity Coverage may not return your Lithium-Ion Battery to an “as new” condition with the original 100% battery capacity. However, it will provide the vehicle with an EV Battery capacity of at least 70% of the original battery capacity. This Lithium-Ion Battery Capacity Coverage is subject to the exclusions listed under the section “What is Not Covered.”

Electric Vehicle Warranty FAQ | Kia Soul EV | Kia Cars
---------------------------

That seems like a pretty clear warranty. I don't know anything about what charging controls the Kia Soul EV offers to the owner, so don't know if it is possible to do the equivalent of a "Range" charge or not.

 

[David_Cary]

That's certainly one way to look at it. Also on a kwh basis, Tesla has more.

In the Leaf world, average ambient temperature is the most important factor. That varies (for the most part) at the pack level. So that was my frame of reference. All behavior occurs on a pack level such as depth of discharge, time at 100%, speed of discharge, speed of charge (frequent QCs/SC).

There are certainly battery level issues also but I suspect that has more to do with manufacturer variances. There may also be positional effects of a battery in the pack but I think 192 positions for the Leaf is enough to tease out issues there.

 

[Chickenlittle]

In another thread about Kevin Sharpe's dispute with Tesla over how much battery capacity loss is acceptable before warranty coverage kicks in, @Lump posted this text from the Kia Soul EV battery warranty indicating that up to 30% capacity loss is allowed before a Kia will repair/replace the battery under warranty:

--------------------------------------------------
* Lithium-Ion Polymer Battery Capacity Coverage

The Lithium-Ion Polymer Battery (“EV Battery”) Capacity warranty coverage period is 10 years or 100,000 miles from the Date of First Service, whichever comes first, for capacity loss below 70% of the original battery capacity. This warranty covers repairs needed to return battery capacity to 70% of original battery capacity. If possible, the EV battery components will be repaired or replaced,and the original EV Battery will be returned to the vehicle. If necessary, the EV Battery will be replaced with either a new or remanufactured Lithium-Ion Polymer Battery. Any repair or replacement made under this Lithium-Ion PolymerBattery Capacity Coverage may not return your Lithium-Ion Battery to an “as new” condition with the original 100% battery capacity. However, it will provide the vehicle with an EV Battery capacity of at least 70% of the original battery capacity. This Lithium-Ion Battery Capacity Coverage is subject to the exclusions listed under the section “What is Not Covered.”

Electric Vehicle Warranty FAQ | Kia Soul EV | Kia Cars
---------------------------

That seems like a pretty clear warranty. I don't know anything about what charging controls the Kia Soul EV offers to the owner, so don't know if it is possible to do the equivalent of a "Range" charge or not.

1. His decrease of 19% would not have triggered what he wanted
2. He admitted to many (90 or more range charges). The roadster (not the models) has a warning that comes up with each range charge that doing so frequently will reduce range. He continued this behavior despite experiencing decreasing range over two years. Warranties do not usually cover abuse