Tesla vs Leaf battery degradation

[edatoakrun]

Back to the OP.

IMO, you have made two erroneous assumptions:

="barsad22"
...I come at this as an owner of a 2011 Leaf with 39K miles, and a 79.4% capacity confirmed by Leaf Spy...

Error #1:

Taking your LBC's estimate of capacity loss seriously.

...I just came from a Tesla S test drive, and asked the 19-year-old sales guy some tough questions about Tesla battery degradation over time...

So when he told me that Tesla claims a maximum 0.7% per year degradation...

Error #2:

Believing anything a car salesman tells you.

If you really want to know how the LEAFs battery compares to that of other BEV/PHEV manufactures over time (in the extremely hot climate of Phoenix) watch the AVTA Test results for most BEVs and PHEVs on the American market, at these sites:

http://avt.inel.gov/fsev.shtml

http://avt.inel.gov/phev.shtml

You can't compare The LEAF pack to Tesla's, as none of it's BEVs, or the Toyota and Mercedes Tesla-sourced compliance BEVs, are subject to AVTA testing.

That's really quite odd, and I have no idea why that is.

But you can compare The LEAF pack results to most all the other BEVs and PHEVs, as the results are published.

So far, the very preliminary results for the ATM equipped 2013 Ford Focus E and 2012 I-MIEV don't look to be very significantly superior to the results for the 2013 LEAF, when you consider seasonality. I expect TMS will show significant benefits in battery longevity over the longer term in an extremely hot climate like Phoenix, but whether there is any advantage in either total operating costs, or any mine/well to wheels environmental benefit to ATM, is a much more difficult question.

In the large majority of all climates that are cooler than Phoenix, I expect the LEAFs passive TM will eventually be widely accepted as superior to ATM.

If you look back at the earlier 2011 LEAF test results, designed to show variable capacity loss from DC compared to L2 charging, the first 50k miles of which are summarized here:

http://avt.inel.gov/pdf/energystorage/DCFC_Study_FactSheet_EOT.pdf

You can see how relatively little capacity the LEAF pack loses over 10,000 miles of driving, as long as the battery is not kept at extremely high average temperatures, which is a problem I doubt you have experienced, living in Berkeley.

I have a LEAF almost as old (3/11 build date) and with almost as many miles (~38,600) as yours, and I am quite sure now that my LBC report is significantly overstating the actual capacity loss.

My best estimate is that my LEAF, driven in a much hotter climate than yours, has lost ~13.5% of it's initial capacity to date, as measured in average kWh of charge accepted from the meter, when compared to the average kWh accepted for the four AVTA LEAFs, static tests of which averaged 23.4 kWh.

Or from another perspective, My LEAF's pack is currently ~16% less than the 24 kWh initial static capacity Nissan specified for all 2011-15 LEAFs.

These estimates compare to the ~24 % capacity loss my LBC was reporting last week.

That was prior to my LBC's report of miraculous healing (back up to 76.44%, yesterday) apparently brought on by the combination of extreme battery heating and high capacity use during a three day ~600 mile round trip I made through the 100+ F Central Valley to the Bay area last week.

 

[Stoaty]

Error #1:

Taking your LBC's estimate of capacity loss seriously.

Ed, everyone (except you) takes the estimate of capacity loss seriously. Nissan takes it seriously enough that they will replace the battery pack with a brand new one under warranty (at considerable expense) based on the LBC reading. Of course, Nissan is a non-profit charitable organization only so perhaps their opinion isn't worth much.

 

[dgpcolorado]

...You can bet your bottom dollar they won't be pushing the Model 3 to those extremes. They'll choose a more sensible alignment, rim, tire setup. It'll also help that the car will weight less.

Maybe they do 17" rims standard and 18" as an optional? Maybe they do something else. Whatever they do I'm not worried about drive unit reliability as a concept. They have that under an unlimited mile warranty that is quite consumer friendly...

Since I will be betting my dollars, I sure hope that they get the QC issues solved and dial back the performance stuff (some Tesla fans want the Model 3 to be a pocket rocket). As for the warranty, can they afford to do that with their mass market car? If they have as many issues as the Model S it would bankrupt the company (margins figure to be a lot smaller on the 3).

I hope that Nissan will be able to solve the battery capacity degradation issues because otherwise the LEAF has been a solid car; it is certainly the most trouble-free car I've ever owned. I worry that the Tesla Model 3 won't be the same and being 300 miles — and a whole lot of mountains — away from the nearest service center figures to be an expensive nuisance if the car isn't reliable. Weren't BEVs supposed to be simple and more reliable than ICEVs?

 

[desiv]

I doubt a goodly number of the 2011 through 2013 folks would agree with you...

Nissan did not do nearly as bad a job as everyone seems to think they did

Actually, I think they would.
My guess is the truly unhappy, while justified, are a smaller percentage...

desiv

 

[Deleted member 1622]

Back to the OP.

IMO, you have made two erroneous assumptions:

="barsad22"
...I come at this as an owner of a 2011 Leaf with 39K miles, and a 79.4% capacity confirmed by Leaf Spy...

Error #1:

Taking your LBC's estimate of capacity loss seriously.

...I just came from a Tesla S test drive, and asked the 19-year-old sales guy some tough questions about Tesla battery degradation over time...

So when he told me that Tesla claims a maximum 0.7% per year degradation...

Error #2:

Believing anything a car salesman tells you.

Ed -
Apparently you missed the obvious context clues (the sales guy is less than half my age and I use the word "claims" for Tesla's numbers) that demonstrated that I do not believe ANYTHING a sales guy says (especially the one from Nissan, who assured me in 2011 that I wouldn't go below a 20% loss in 5 years).
The problem is, I don't believe anything you're saying, either, because in the end most of what we're saying in this forum is speculation or opinion based on an N of 1 (or a few).
There is no solid information in a "Consumer Reports" type of format that compares one BEV to another on the degradation numbers. Those links to the AVTA you included are interesting from a techie/engineering standpoint, but as you point out some of the key cars aren't even studied by AVTA, and I don't see clear evidence on real-world degradation in those tests. From this helpful video that drees posted (http://mynissanleaf.com/viewtopic.php?f=9&t=15796#p352669) I learned that the "simulate 8 years of charging in six weeks" testing regimen that most companies did on these original batteries was pretty useless scientifically.
I wish one of the many EV driver associations out there would spend some membership money on long-term degradation testing rather than those EV parties aimed at promoting EVs (and everyone who attends already owns one). I'm up for donating $100 as soon as I hear about the testing grant.

Josh

 

[Zythryn]

...
I wish one of the many EV driver associations out there would spend some membership money on long-term degradation testing rather than those EV parties aimed at promoting EVs (and everyone who attends already owns one). I'm up for donating $100 as soon as I hear about the testing grant.

Josh

www.pluginamerica.com does statistical studies.

http://gas2.org/2015/02/20/tesla-loss-battery-range-less-feared/

 

[keydiver]

Hello --
I just came from a Tesla S test drive, and asked the 19-year-old sales guy some tough questions about Tesla battery degradation over time.
I come at this as an owner of a 2011 Leaf with 39K miles, and a 79.4% capacity confirmed by Leaf Spy.
So when he told me that Tesla claims a maximum 0.7% per year degradation (let's call it 5% over 5 years), my jaw dropped.

As others have said, Tesla is now several generations (or perhaps "tweaks") away from their original chemistry, so its very hard to say how much degradation their current cells will experience. But, if you haven't seen Dr Dahn's video, I suggest watching it when you have the time, especially starting around the 25 minute mark, where he starts highlighting the differences between the chemistry chosen by different EV manufacturers:
https://www.youtube.com/watch?v=pxP0Cu00sZs

You can see that the Tesla cells suffer a lot less degradation, especially heat-related damage, than the Leaf cells, and this was older tech. With him working along with Tesla now, I have high hopes that they will keep pushing Li-ion technology ahead rapidly. If you watch the entire video, you will see that he has developed a method of testing that can accurately predict longterm degradation issues.

 

[DaveEV]

I wish one of the many EV driver associations out there would spend some membership money on long-term degradation testing rather than those EV parties aimed at promoting EVs (and everyone who attends already owns one). I'm up for donating $100 as soon as I hear about the testing grant.

http://www.pluginamerica.com does statistical studies.
http://gas2.org/2015/02/20/tesla-loss-battery-range-less-feared/

They may be studies, but they're based on user-surveys and not actual testing which is somewhat useful, but hard to draw reliable conclusions from.

The big problem with a "real life" capacity loss study, is that by the time you're halfway done, the manufacturers are already shipping update chemistries which may perform significantly different than what you're testing.

 

[TonyWilliams]

My opinion is that for consumers, nothing really beats the empirical tests for determining battery performance. Obviously, any short term accelerated test doesn't test the all-important variable of real time. The often quoted Plug-In America "study" is anything but a study.

For Ed's car, with his 76% capacity reported, I'm quite confident that it would actually go about 76% of the new range in a CONTROLLED test.

Ed, unfortunately, is like the climate change denier. Here's a public comment made by him from a few years ago that illustrates his reluctance to facts, with the same broken record of whackadoodle spinning in his head. It's important to note that in reference to the post below, that:

1) The vehicles were driven on cruise control; there was not variable speeds or "variable human" inputs, and this was in the report

2) The temperatures were identical and reported

3) VLBW issue is somewhat bizarre, even for Ed, but is addressed in the report

4) Regenerative braking is the same at fixed speeds over fixed courses

5) Stabilizing temperature in a car sized battery doesn't take "several days"!!!


Anyhoo, it's a broken record, spinning at the same broken speed, over and over.

***********

New comment on post "Nissan LEAF Side by Side Range Comparison: 2012 vs 2013"
Comment by JohnL, responded to by Ed Marek (IP: 74.42.190.69)

March 11, 2013 at 2:14 pm

>>>> As the driver of the 2013 Leaf used in the test, I was disappointed in the results, too. That said, I thought Tony’s test and write up were excellent, thorough and transparent..." <<<<

Not exactly.

In my opinion, this range test was far too poorly designed and reported to reach very accurate conclusions.

However, JohnL, if you and the other LEAF driver who actually drove their LEAFs can report a few of the facts and results omitted from this article, we still should be able to recover some useful results from your time and effort.

The three greatest errors in the design of this range test, IMO, were in the failure to test both cars to the same minimum charge level (VLBW), the failure to report driver (human and cruise control) efficiency, and the failure to normalize and report battery temperature when charging.

The first error cannot be corrected now, but you could help us to eliminate some of the inaccuracy introduced by the two others, and allow us to still get some useful information from your work.

As a few commentators have noted, the amount of regenerative braking almost surely varied between the two test cars. What they don’t seem to realize is that both of these LEAFs were capable of reporting the regenerative braking charging history through the CarWings telematics system.

So, assuming both drivers were using CarWings, each should have a report of actual regen charging during this test. And of course, IF each driver received the same regen kWh, while driving identical speeds, while using the same kWh in total (also reported by CarWings) then driver efficiency was identical.

If you both could please post those results, we can significantly reduce the inaccuracy of this report.

Another large uncontrolled test variable was battery temperature.

The report of five bars of temperature in the dash display only indicates the battery temperatures were within ~25 F of each other.

The total charge accepted by the LEAF battery will vary by approximately 3% to 4% in this temperature range (less kWh of charge are accepted by a colder battery) and the range from a subsequent test will vary by about the same percentage.

So the only way to accurately range test two LEAFs, is to have them exposed to close to identical ambient temperatures and same charging and discharging schedule (both of which cause battery heating) for several days before the test.

Apparently, this was not done here.

If you and the other driver could report the ambient temps and driving history, for the day or two previous, we could still get a better idea of your initial charge variations due to battery temperature, and reduce the inaccuracy of the test results even further.

Of course, eventfully a competent party will have the opportunity to run a range test between the 2012 and 2013 LEAF, and do it right to begin with, giving far more accurate results than we can recover form this effort.

You can see all comments on this post here:

http://insideevs.com/nissan-leaf-side-by-side-range-comparison-2012-vs-2013

Permalink: http://insideevs.com/nissan-leaf-side-by-side-range-comparison-2012-vs-2013/#comment-58857

 

[edatoakrun]

barsad22

Ed -
Apparently you missed the obvious context clues (the sales guy is less than half my age and I use the word "claims" for Tesla's numbers) that demonstrated that I do not believe ANYTHING a sales guy says...

I understood you, I was just trying (perhaps not as humorously as intended) to make the point that what anyone at Tesla tells you is likely irrelevant to the subject.

barsad22
The problem is, I don't believe anything you're saying, either...

IMO, whether you believe me or not, shouldn't matter much to either of us.

As I suggested above, If you consider the AVTA reports on LEAF battery capacity, and if you find them credible, it's likely you estimate you own battery pack's capacity, with considerable accuracy.

What concerns me is that you imply that you do believe your LEAF's LBC report of:

barsad22...79.4% capacity confirmed by Leaf Spy....

Since you have not stated what data your LBC "confirmed", it sounds like you may have just assumed that that report is correct.

If so, you are hardly alone.

The only real argument any proponent of relying on LBC data has ever made, as was repeated above in another post above, can be summarized as:

We all believe this bullshit, so you should too.

I don't know what your LEAFs present actual battery capacity, either available or static, is.

I can only tell you what my own estimate of my LEAFs capacity loss is, which I already did above.

Since all evidence indicates that my LEAF's OE pack, which has endured far hotter Summer temperatures than yours, has lost a far smaller percentage of its initial capacity than what your LBC indicates, I think it's quite likely you will find a far lower actual capacity loss than 20.6%.

If you decide you want to know...

There are plenty of data available from the AVTA reports for most any LEAF owner to estimate their current battery capacity, either by measuring the energy output from range/capacity tests, the kWh your LBC allows you to discharge, or by measuring the energy accepted, from metered measurements of the kWh your LBC allows your pack to accept following discharge.

Most of those with the geographic advantages of living in California's coastal climate zones, should find this easier than most others, since there is such a large window of seasonality when you can approximate the Phoenix Winter battery pack and ambient temperatures under which most of the AVTA results were compiled.

Anyone can find detailed posts on how I've been monitoring my pack's available capacity for the last 4+ years, and how I've arrived at my estimate of my pack's loss of static capacity from those observations, on other threads.

But I'd actually prefer you (or anyone else) work out your own methods, as many LEAF drivers are in locations and have driving patterns that should allow more precise results than I'm likely ever to be able to achieve.

 

[GetOffYourGas]

My best estimate is that my LEAF, driven in a much hotter climate than yours, has lost ~13.5% of it's initial capacity to date, as measured in average kWh of charge accepted from the meter, when compared to the average kWh accepted for the four AVTA LEAFs, static tests of which averaged 23.4 kWh.

When you say "from the meter", I assume you are measuring from the wall somehow? With a Kill-A-Watt or equivalent device? The problem with this method is that as a battery degrades, its internal resistance increases. I think this is reported somehow on LeafSpy? Hx maybe? Well, an increased internal resistance will result in more power lost during charging. In other words, your wall-to-battery efficiency actually goes DOWN. I don't know how much it goes down by, personally. Is it enough to make it look like your battery is healthier than it is? Remember, measuring from the wall includes the energy going into the battery AND that which is lost to charger inefficiencies, the cooling pump, internal resistance, etc.

 

[RegGuheert]

When you say "from the meter", I assume you are measuring from the wall somehow? With a Kill-A-Watt or equivalent device? The problem with this method is that as a battery degrades, its internal resistance increases. I think this is reported somehow on LeafSpy? Hx maybe? Well, an increased internal resistance will result in more power lost during charging. In other words, your wall-to-battery efficiency actually goes DOWN. I don't know how much it goes down by, personally. Is it enough to make it look like your battery is healthier than it is? Remember, measuring from the wall includes the energy going into the battery AND that which is lost to charger inefficiencies, the cooling pump, internal resistance, etc.

While the increased resistance may be enough to affect your range while driving, it is not a significant effect (in terms of increasing the apparent capacity of the battery) when charging at 3.3kW. By my calculations, there should be less than a 0.5% increase in power drawn from the wall due to additional resistance (less than 15W out of 3.3kW).

OTOH, the additional resistance WILL noticeably *reduce* the recharge capacity of the 2011 LEAF when charging at 3.3kW since the LEAF's BMS uses a fixed voltage at which to cut off charging. If we assume 8.5A charging current at cutoff and an additional 0.15ohm of total resistance (same assumptions as above), then the terminal voltage of the highest cell will only charge to 4.086V instead of the 4.1V when new. This could result in a few percent loss of range due to the inability to fully charge the battery. This is seen by owners when the first couple of charge bars at the top drop much faster than when the vehicle was new (and much faster than the other bars). The workaround for this issue is to charge on L1 when you want to make long drives. (The L1 workaround also improves cell balancing, which can further improve range from a full charge.)

 

[desiv]

The workaround for this issue is to charge on L1 when you want to make long drives. (The L1 workaround also improves cell balancing, which can further improve range from a full charge.)

Hmm.
Makes me wonder, should I throw in an L1 charge once a month or so for good measure?
I haven't used my L1 since I got my L2 EVSE...

 

[GetOffYourGas]

Thanks for putting some numbers to my thought. I really have no way of knowing what the internal resistance values actually are.

Interesting note regarding charging. I thought that the charger just continued to ramp down the current until the battery is topped off. When the charger stops, the "rest voltage" of the battery will float back down to the true value of the cells (as the current goes to zero, the voltage drop, too, goes to zero). I almost always charge to 80% on L1, so I probably wouldn't see this effect myself anyway.

 

[RegGuheert]

Interesting note regarding charging. I thought that the charger just continued to ramp down the current until the battery is topped off. When the charger stops, the "rest voltage" of the battery will float back down to the true value of the cells (as the current goes to zero, the voltage drop, too, goes to zero).

The MY2013 and later do a very good job of this, even though they have a higher-power charger. But the MY2011/2012 do not taper very well. At L1, I have observed virtually zero taper all the way up to the termination point. At L2, there is a bit of taper, but it's not enough to get the battery fully charged.

I believe one reason (among others) the MY2013 is showing lower battery degradation is because of this improved charging algorithm.