Capacity Loss on 2011-2012 LEAFs

[davekern]

Facts on my Leaf. I had it just less than two years and put about 28k miles on it. In the end I was lucky to get 55 miles on a charge with mixed town freeway driving, about equal. Freeway driving was scary. To get that I was driving well under the speed limit, white knuckled. I was down two capacity bars and calculated my range was about 30% decreased. I have great records as I recorded my miles each day for tax purposes.

I bought a RAV4 last night. Probably could have gotten a better deal going to LA, but I don't have a day to spend on it right now. I got a fair deal here in town. I drove it today for 78 miles mixed driving but more freeway than normal. I had a side trip, so it was more driving than my typical day. I went with the speed of traffic 70+ driving like our ICE cars. I got home with 25% bars left. It drove great, tons of power. No concern going at least 100 miles on a full charge with my typical driving. Only complaint for it compared to Leaf is a little more road noise. If I can keep the range, with the better battery system, I will be very happy and it will be worth the premium.

I can't knock Nissan though, they stepped up when they could see that the car was well taken care of but the batteries were deteriorating very rapidly.

 

[cwerdna]

^^^
Interesting... when you mention that you were getting about 55 miles on a charge, when you arrived home/your destination, how many fuel bars were you down to (or better yet, gids)? Did you trigger LBW, VLBW or turtle when you arrived?

Yeah, I'd imagine you'll have no probs w/100 miles on a charge if you do an extended charge on the Rav4 EV.

I have it on good authority that Yanquetino's LEAF lost a bar yesterday.

Poetic justice.

It'll be interesting to know if he loses another 1 or 2 once this summer begins and ends. And, it'll be interesting to know how the remapping works via the firmware update...

 

[TonyWilliams]

It'll be interesting to know if he loses another 1 or 2 once this summer begins and ends. And, it'll be interesting to know how the remapping works via the firmware update...

Maybe we should start a Kerfluffle thread.

 

[scottf200]

http://insideevs.com/scientists-confirm-high-temperatures-permanently-shorten-life-of-lithium-ion-batteries" onclick="window.open(this.href);return false;

Scientists Confirm High Temperatures Permanently Shorten Life of Lithium-Ion Batteries
10 hours ago by Eric Loveday

Source at bottom of that article (ACS).

 

[TomT]

Well, I'm now down two bars and it isn't even very warm yet... I'm certain I'll lose a third before summer is out! At this rate, I expect it to be be down 4 to more likely 5 bars when the lease is up in 2015.

 

[DaveinOlyWA]

high temperatures? 86º is now considered too hot? that leaves Phoenix in trouble for what? 10½ months a year now?

 

[cwerdna]

high temperatures? 86º is now considered too hot? that leaves Phoenix in trouble for what? 10½ months a year now?

Heh. Yeah, I saw that earlier today. 86 F is really bad news for folks in Phoenix.

I posted some temps from a Phoenician Prius owner (who DaveinOlyWA should know too) at http://www.mynissanleaf.com/viewtopic.php?p=215907#p215907" onclick="window.open(this.href);return false; long ago.

 

[tbleakne]

http://insideevs.com/scientists-confirm-high-temperatures-permanently-shorten-life-of-lithium-ion-batteries

Scientists Confirm High Temperatures Permanently Shorten Life of Lithium-Ion Batteries
10 hours ago by Eric Loveday

Source at bottom of that article (ACS).

Right topic, but not enough detail, at least in the review of this paper. I am disappointed by this quote:

To test the limits of lithium-ion EV batteries, Cugnet’s team reconstructed the experience of a typical EV battery in the laboratory. Using data gleaned from a real five-mile trip in an EV , they put EV battery packs and cells through simulated lifetimes of driving with cycles of draining and recharging.

 

[DaveinOlyWA]

high temperatures? 86º is now considered too hot? that leaves Phoenix in trouble for what? 10½ months a year now?

Heh. Yeah, I saw that earlier today. 86 F is really bad news for folks in Phoenix.

I posted some temps from a Phoenician Prius owner (who DaveinOlyWA should know too) at http://www.mynissanleaf.com/viewtopic.php?p=215907#p215907" onclick="window.open(this.href);return false; long ago.

I wish the article had a bit more detail. it was pretty vague as to how much time over 86º was needed to cause permanent degradation. it was pretty clear in stating the performance was affected so have to think X time over 86º will cause the permanent degradation.

but there was a general confusion over what temp was dangerous and I had the impression that selected areas in the SW were the most vulnerable thinking temps had to regularly be at least in the mid 90's or so but 86 is something common thru out most of CA including relatively mild places like inland Orange County, etc. Dont even consider Riverside or anything like that.

lot of difference between mid 90's and mid 80's... probably about 50-60 million people worth of difference

 

[smkettner]

Put the fan in the garage window tonight. Charging has started pushing me to six bars lately. Prefer to be at five as much as possible.

 

[DaveEV]

http://insideevs.com/scientists-confirm-high-temperatures-permanently-shorten-life-of-lithium-ion-batteries

Scientists Confirm High Temperatures Permanently Shorten Life of Lithium-Ion Batteries
10 hours ago by Eric Loveday

I really hate Eric Loveday's articles. They are almost always written to stir up the crap and also brought the "Autoblog" style of writing to InsideEVs. Most of his articles show little to no actual knowledge of EV technology, too. Really disappointing.

Anyway, I posted this comment on InsideEVs:

Duh?
It is well known that lithium batteries degrade faster at higher temperatures, it’s effects can be approximated by using the arrhenius equation which states that for every increase in temperature of 10C, the battery will degrade about twice as fast.
Now at some temperature different chemical reactions may occur which speeds up the rate of degradation faster than the arrhenius equation predicts, but this temperature varies depending on the specific lithium chemistry in question.

Anyway, without access to the actual paper, it's impossible to see what the researchers actually tested.

 

[scottf200]

Anyway, without access to the actual paper, it's impossible to see what the researchers actually tested.

The ACS hyperlink in that article takes you to here (and it has media contacts):
http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTICLEMAIN&node_id=222&content_id=CNBP_032579&use_sec=true&sec_url_var=region1&__uuid=da7ef387-505e-4a40-9803-1339fb490d47" onclick="window.open(this.href);return false;

NEW ORLEANS, April 10, 2013 — Scientists today answered a question that worries millions of owners and potential owners of electric and hybrid vehicles using lithium-ion batteries: How long before the battery pack dies, leaving a sticker-shock bill for a fresh pack or a car ready for the junk heap? Their answer, presented here at the 245th National Meeting & Exposition of the American Chemical Society (ACS), being held here this week, may surprise skeptics.

“The battery pack could be used during a quite reasonable period of time ranging from 5 to 20 years depending on many factors,” said Mikael G. Cugnet, Ph.D., who spoke on the topic. “That’s good news when you consider that some estimates put the average life expectancy of a new car at about eight years.”

Cugnet explained that the lifespan depends mainly on the battery’s temperature, state of charge and charge protocol. Battery performance begins to suffer as soon as the temperature climbs above 86 degrees Fahrenheit. “The higher the temperature, the lower the battery service life,” he said. “A temperature above 86 degrees F affects the battery pack performance instantly and even permanently if it lasts many months like in Middle East countries.”

 

[tbleakne]

Put the fan in the garage window tonight. Charging has started pushing me to six bars lately. Prefer to be at five as much as possible.

Last Fall I installed a small window A/C in my garage, and last month I added ceiling insulation. On cool nights I run a fan. Lately I have been able to get the garage several degrees below 60 F overnight. Most all Winter I have been at 5 Tbars, with several exceptions. If I arrive home and find the garage warmer than ambient, I park outside until I can cool off the garage.

I expect to keep the garage peak temperature 10-12 degrees F below ambient through most of the summer. August and September are usually 85-95 F. I have significant solar credit from Time-of-Use billing to pay for the A/C.

Here is my latest capacity loss data, based upon %Gids at "80%" charge. I no longer charge to "100%", but when necessary, once a month or so, I charge to "100%" - 3% Gids. The top 3 Gids contain very little mileage; all the rest of the Gids track consistently close to 1 level mile per %Gid. I have fine-tuned my driving such that my dashboard has averaged 5.1 to 5.2 miles/kWh for last 2 months.

I am surprised at how much temporary rebound has occurred following especially cool weather in November and earlier this month. However, the data also shows that I can expect to lose this rebound again very quickly once temperatures warm. My temperature data is too imprecise to publish, since what really matters is pack temperature, and that is not yet available on the Gid meter, Generally, however, seeing the 6th Tbar appear for more than a few hours in the afternoon is enough to trigger decline.

I am hoping my aggressive temperature mitigation efforts will slow the rate of decline as I begin my 3rd year at the beginning of June. Last Summer the decline rate was 1.4% Gids per month.

 

[KJD]

My temperature data is too imprecise to publish, since what really matters is pack temperature, and that is not yet available on the Gid meter,

That might change in the near future.
http://www.mynissanleaf.com/viewtopic.php?f=44&t=5304&start=70" onclick="window.open(this.href);return false;

 

[Stoaty]

Here is my latest capacity loss data, based upon %Gids at "80%" charge. I no longer charge to "100%", but when necessary, once a month or so, I charge to "100%" - 3% Gids. The top 3 Gids contain very little mileage; all the rest of the Gids track consistently close to 1 level mile per %Gid. I have fine-tuned my driving such that my dashboard has averaged 5.1 to 5.2 miles/kWh for last 2 months.

I don't understand the chart. You started the second year with 98% capacity retention on an 80% charge? What Gid count is 100% capacity for an 80% charge? How are you doing the calculations? Please clarify.

 

[mksE55]

Well it happened. Add me to the 2nd Bar loss table. 20,651 mileage. got up today and now its gone. cars not even 2 yrs old. I will call Nissan and report the next bar loss. this doesnt bode well for 20% loss in 5yrs or 70% loss in 10yrs. come on Nissan step up and correct this.

 

[edatoakrun]

Well it happened. Add me to the 2nd Bar loss table. 20,651 mileage. got up today and now its gone. cars not even 2 yrs old. I will call Nissan and report the next bar loss. this doesnt bode well for 20% loss in 5yrs or 70% loss in 10yrs. come on Nissan step up and correct this.

Can you, and others with capacity bar losses, discharge your battery to LBW or VLB and report back on the 16 A 240 V recharge time to "80%", and the approximate battery pack temperature during that recharge session?

This simple observation may provide a fairly accurate measurement of your LEAF's actual available capacity loss , as opposed to the capacity bar display.

The relatively slight reduction in my LEAFs VLB to "80%"charge time, as well as the almost imperceptible loss of range in my multiple range tests from "100%" to VLB, is why I may not worry too much if and when I lose my first capacity bar ~on schedule, for a ~2 year old ~20,000 mile "warm" climate LEAF, later this Spring or Summer.

Another ~VLBW to "80%" timed charge result to post.

Following my 4/2/13 range test, it took ~4 hours and 14 minutes to recharge, after a reported 15.7 kWh use.

This compares with:

Quote:
..16 amp 240v recharge (following the 9/8/12 range test)....took 4 hours and 16 minutes to reach 80% (and another one hour and 11 minutes to reach “100%”) following this trip...(after a reported 16.7 kWh used).

This compares to a recharge time of ~4 hours 25 minutes to reach “80%” following my first range test, on 9/7/11, with a reported 18.7 kWh used from 100% to about the same capacity level, ~VLBW.

http://www.mynissanleaf.com/viewtopic.php?f=31&t=9064&start=30" onclick="window.open(this.href);return false;

So, assuming a constant charge rate to "80%", and that "80%" is a constant percentage of total battery capacity, both of which seem to be largely accepted, I think this is further evidence that my LEAF's available battery capacity has not declined very significantly since 9/7/11, and the kWh use reports from CW, which are used to calculate both my dash and nav screen m/kWh, are probably significantly lower than actual, as is also my conclusion from the range tests results.

I expect that the lower capacity and lower charging efficiency of my ~50 f battery (as opposed to the ~75 F battery during the 2011 and 2012 Summer tests) both had some effects on the charge time after the 4/2/13 range test, so I think those results are not as definitive as those I'll be able to collect once the weather heats up to "summer" conditions.

http://www.mynissanleaf.com/viewtopic.php?f=31&t=6876&start=200" onclick="window.open(this.href);return false;

 

[RegGuheert]

The relatively slight reduction in my LEAFs VLB to "80%"charge time, as well as the almost imperceptible loss of range in my multiple range tests from "100%" to VLB, is why I may not worry too much if and when I lose my first capacity bar ~on schedule, for a ~2 year old ~20,000 mile "warm" climate LEAF, later this Spring or Summer.

Ed, it appears that over 19 months your instruments have reporting a 16% reduction in battery capacity used while your recharge time to 80% has dropped just 6%.

If these recharge tests were following the same drive, why do you think the recharge time has decreased? Slightly improved driving efficiency (but not nearly as much as the instruments are telling you)?

 

[TomT]

My percentage loss of capacity - my Lincomatic Gid meter and the capacity bars aside - is backed up by the actual decrease in range that I have experienced. Both track fairly close to each other making me believe that the capacity loss is real and fairly accurately portrayed.

 

[edatoakrun]

The relatively slight reduction in my LEAFs VLB to "80%"charge time, as well as the almost imperceptible loss of range in my multiple range tests from "100%" to VLB, is why I may not worry too much if and when I lose my first capacity bar ~on schedule, for a ~2 year old ~20,000 mile "warm" climate LEAF, later this Spring or Summer.

"RegGuheert

Ed, it appears that over 19 months your instruments have reporting a 16% reduction in battery capacity used while your recharge time to 80% has dropped just 6%...

The problem is that on battery which seems to have as little capacity loss as mine, the uncertainties (IMO) are larger than your statement implies.

First, note that the 16% decrease you calculated is from a hot to cold battery. That's why I said I should get a much better read when ambient temperatures increase, or I get access to a DC charger to heat up my pack in order to dope my capacity to mid-summer temps. Next note the CW kWh use is only reported to the nearest 100 Wh, or ~ +/- .6%, for a ~16 to 18 kWh discharge.

And all my recharge times are from adding up two or three recharge sessions (I always recharge from VLBW for ~ one hour immediately after a range test to ~VLBW) both rounded to the nearest minute, so their is another +/- of ~1% for the time.

="RegGuheert ...If these recharge tests were following the same drive, why do you think the recharge time has decreased? Slightly improved driving efficiency (but not nearly as much as the instruments are telling you)?

I think my recharge time has decreased because I have lost some capacity. I just don't think you can say "6%" with any precision, more like ~6%, +/- ~4%.

I think my driving efficiency (in terms of avoiding regen) has improved by ~ a few percent, as the CW regen reports seem to have shown.

But there are other efficiency improvements CW cannot show, any decrease in disc brake use and any increased efficiency I am getting by varying my speed less (and thus using less atmospheric braking) over my timed test route.

And I suspect there might be some increase in drive train efficiency over time, in both drive train friction reductions and reduced tire rolling resistance, which throws another unknown variable into the equation.

The important point, IMO, is that all these uncertainties should be fairly constant between LEAFs, and a much lower % of total capacity loss, for those batteries that have more capacity loss than mine, due to higher ambient temps, more recharge cycles, or any other "aging" factors

That's why I think checking recharge times for LEAFs with multiple bar losses, and also LEAFs whose drivers suspect significant capacity loss for other reasons, could be a simple step that might be very informative.