Capacity Loss on 2011-2012 LEAFs

[Stoaty]

However I seem somewhat more concerned about gradual loss than you, because I am not confident that the rate of loss is going to slow down before Fall.

Yes, but I am looking at it from a full year perspective. Since I had 5.3% loss the first year I figure worst case for me is 75% loss at 5 years. If loss is steeper at the beginning as Nissan claims, I should be able to retain 80% capacity at 5 years. As you said, my car spends more time at cooler temperature since I live 4 miles from the coast.

I would suggest one additional rule-of-thumb for modest rate of capacity loss: how much time the car spends at 5 bars.

Agreed. This is a good rule of thumb:

7 bars - very bad
6 bars - slightly bad
5 bars - good
4 bars - best (from a capacity loss perspective)

Of course time at 4 bars each day would be even better.

I keep thinking of Abasile and how well his pack is doing. Those cool mountain temperatures don't seem to be hurting his pack any.

[smkettner]

Not sure I agree 6 bars is slightly bad. Trouble is the range is so great for #6. If you are bouncing 6-7 then I would count it as much worse than bouncing 5-6.

[linkim]

I just came across an article by John Gartner (Senior Analyst at PIke Research) that summarizes some data (from EERE/DOE and national lab research) on the issue of thermal management of Li-ion batteries and the role on battery capacity.

http://www.plugincars.com/lithium-ion-b ... 22447.html" onclick="window.open(this.href);return false;

To quote: “As the accompanying EERE graphic shows, batteries exposed to hotter average temperatures lose their ability to store energy; the hotter the temperature the faster they lose their storing ability. So BEV owners in Phoenix will likely be looking to replace their batteries faster than owners living where the thermometer doesn’t often reach 110°F.”

There isn’t much specifics on battery chemistry, but the results are from research conducted by NREL, and based on NCA/graphite (Dow-Kokam is mentioned in one presentation I saw) . Furthermore, the results were not obtained with a battery pack not necessarily under operating conditions in real life, and are directed at PHEV technology. Nevertheless, the trend of the results are not very surprising with respect to the geographic location and temperature on loss of battery capacity as a function of time. The data suggests that with no cooling, the Li-ion battery capacity will decrease to 80% in 5 years in Phoenix.

These results may not be comparing apples-to-apples because of battery chemistry, testing protocol, etc. with the LEAF battery capacity fade, but adds to the observations some owners are reporting on the effect of temperature on battery capacity fade. Stay tuned.

[LEAFfan]

The data suggests that with no cooling, the Li-ion battery capacity will decrease to 80% in 5 years in Phoenix.

It doesn't sound like valid data to me when there are at least 2 LEAFs here that are already less than 80% and many more will likely be less than 80% before summer ends.

[GaslessInSeattle]

tomorrow we begin the relay of Tony's car back to CA. It's quietly resting in my garage right now. There should be some very interesting data from all the continuous quick charging up and down WA and OR. I would be very surprised if the short term temperature spikes of quick charging come anywhere close to being as damaging as continuous high ambient temps.

[EdmondLeaf]

I agree, in what is described as hot climate battery have no rest at all without TMS or any active method of cooling battery. I am not driving car for a week already, and I am able to keep car battery in the range of 73 -79F (5 - 6 TB border) while temp outside is: high 95 and low 72F. We have heat dome building so real heat will start this week. The highest battery temp was 89F so far and was very consistent with outside temp while car in the shade all time. My shallow battery temp cycling in garage have about 6 h delay and lowest battery temp is around noon.
I can do experiment like that, it will be for 4 mo, because of carpooling and I have normal car to use. My friend Leaf is only car so will be interesting to see results at the end of summer. Bad part I won't be using cheap energy rate that we have during summer, but expect that less battery degradation will be much much grater value than savings on electric bill.

[Volusiano]

I'm owner #5 from Phoenix on the 1 capacity bar lost list. I thought I'd report in some numbers on my out-and-about driving today for your reference.

I started out at 100% charged, 6 temperature bars in the garage. Battery temperature went up to 7 bars pretty quickly and pretty much stayed at 7 bars the whole time until I got home with 2 bars and 14 miles left on the GOM, logging 55 miles total. Car has about almost 18K miles and 1 year 3 weeks of ownership.

No highway/freeway driving at all. Strictly small roads driving at around 40 mph with traffic light just about every mile/block. AC set at 80F and running the whole time. Phoenix high today was 108C. Whole trip was between 4-10pm with 2 stops in between and 1 stop on return.

I reached my final destination at 7pm and 29 miles later and 5 bars left (7 bars gone). On the way back with sun down, I reset my efficiency meter and tried to drive as efficiently as possible and got 5.7 miles/kwh. Odometer read 55 miles for total trip when I got home, with 14 miles left on GOM.

So the bottom line is that with 100% SOC and 1 capacity bar lost, it looks like I was able to squeeze about 69 miles out of the car (55 actual + 14 GOM remaining) with 40mph avg city driving and using AC in Phoenix summer weather. I was hoping for a little bit lower than in the neighborhood of 85 miles total (based on 85% capacity remaining). I know that AC would eat into my hope for 85 miles quite a bit. But I don't know if AC would eat 16 miles of of the 85 or not (rendering the usable range at 69 miles).

An interesting observation is that departure to destination took 7 bars but return took only 3 bars. However, departure was 29 miles while return was 26 miles. Also on the return, the sun was already down, and I also tried to drive more efficiently. But to lose 7 bars on departure and only 3 bars on return seems to imply that maybe the SOC bar is not perfectly linear. I don't know, it always seems like it's never been linear in the first place, based on my previous experiences with it anyway.

[Herm]

An interesting observation is that departure to destination took 7 bars but return took only 3 bars. However, departure was 29 miles while return was 26 miles. Also on the return, the sun was already down, and I also tried to drive more efficiently. But to lose 7 bars on departure and only 3 bars on return seems to imply that maybe the SOC bar is not perfectly linear. I don't know, it always seems like it's never been linear in the first place, based on my previous experiences with it anyway.

Its not linear, graphs have been posted.. thats why a gidometer is a good idea, get the real number and not the manipulated data. Perhaps the amount of GIDs in the range bars get adjusted as the battery ages and loses capacity. You also tried to drive more efficiently on the way back.

[JPWhite]

An interesting observation is that departure to destination took 7 bars but return took only 3 bars. However, departure was 29 miles while return was 26 miles. Also on the return, the sun was already down, and I also tried to drive more efficiently. But to lose 7 bars on departure and only 3 bars on return seems to imply that maybe the SOC bar is not perfectly linear. I don't know, it always seems like it's never been linear in the first place, based on my previous experiences with it anyway.

I typically get 5-7 miles per bar depending on my driving speed/style.

On you outward journey you got just over 4 miles per bar, on the return over 8!!

Driving style and average speed are huge factors determining range in an EV. I suspect it's the way you drove that made the lion's share of the difference. I find A/C subtracts, at most, 4 miles from my range.

[EdmondLeaf]

Temp bar 7 (98 to 122F) that is in the battery warranty voiding area. Today for the first time we will have 105F here, I am not heat transfer technologist or battery expert and driving in that temp is too much for my comfort. Limit should be set by manufacturer disabling vehicle when battery temp is close to danger zone, because there is no way to control or know what actual battery temp really is.