Capacity Loss on 2011-2012 LEAFs

[DaveinOlyWA]

No kidding! I guess "hot" means 80??

 

[surfingslovak]

Come on you guys, this is precisely why we started working on an aging model last year, and why Stoaty has put so much effort into it. While our information is limited and the data noisy, Stoaty's current calibration of the model demonstrates that it's possible to predict degradation based on the Arrhenius equation fairly accurately. Capacity loss can be anticipated and predicted based on the relative impact of the local climate.

If you take Phoenix as aging factor 1, then SoCal is roughly 1.5, NorCal is 2.0 and Seattle is 3.0. The aging we are dealing with seems to be strictly related to the speed of the underlying chemical reactions. In hot climates like Phoenix and Texas, there appears to be an added component, which ages these batteries a bit faster. It almost looks like there was a change to the composition of the battery due to high heat in those locales, which could account for some additional loss of capacity.

Yes, the new hot battery won't be a panacea, but it should be significantly better than the current chemistry, which frankly, looks to be highly sensitive to heat, and likely won't live up to expectations many owners had placed on it. I think those that asked Nissan to add some form of active cooling, even if it was a simple fan inside the battery case, might get another opportunity to argue their point, as the reality of the current battery chemistry starts hitting home. Nissan would be well advised to use the new hot battery in every future LEAF, and not just in the vehicles destined for Arizona, Texas or Abu Dhabi, to use one of Mark Perry's old quotes.

 

[abasile]

It appears that our LEAF's capacity is very close to that of ColumbiaRiverGorge, so I expect we'll loose a bar quite soon. Our latest GID values are 196 at 80% ("69.7%") and 233 at 100% ("82.9%"), with 40,764 miles and 29 months of ownership. (Sorry, no Android battery app yet...)

While our LEAF's pack cools down every night up here above 6100' elevation, it seems clear that the biggest capacity killer has been using the LEAF to commute to a job in the hot valley below, at 1200' elevation. I have to leave the LEAF sitting at 75% charge (real SOC, not GIDs) all day in order to return home. On warm and hot days, the pack temperature reaches six bars around the time I leave the office, and the subsequent drive up the mountain heats it further. (A TMS that cools the pack while driving could put a real dent in this...)

I should add that, during the first year of ownership, I worked at home and the LEAF spent less time down the mountain. It appears that the majority of the degradation has been in the latter 1.5 years of ownership. (I also think the jury is still out on the question of whether the rate of loss slows over time.)

 

[TonyWilliams]

(I also think the jury is still out on the question of whether the rate of loss slows over time.)

I don't think that jury is ever coming back!! It doesn't slow. That was Mark Perry, et al, telling us whatever would kick the can down the road.

 

[smkettner]

It may slow if you were to drive less in proportion to the capacity loss.
But we don't drive less. We go to 100% more and charge any time we can regardless of heat just to drive as we did from the start.
In effect the battery get used harder and harder as it ages.

 

[TonyWilliams]

It may slow if you were to drive less in proportion to the capacity loss.

And it won't degrade as fast at 7500 miles per year and don't drive at freeway speed (Mark Perry). Every statement qualified, but the qualifiers aren't disclosed until push comes to shove.

 

[TimLee]

It may slow if you were to drive less in proportion to the capacity loss.
But we don't drive less. We go to 100% more and charge any time we can regardless of heat just to drive as we did from the start.
In effect the battery get used harder and harder as it ages.

The really big unknown is what does capacity decline rate do after you've lost 30% capacity, or 4 bars 33.75% capacity?
As you push the meager remaining kWh harder and harder, does the degradation rate begin to accelerate?

 

[planet4ever]

I don't think they would replace batteries under nine bars with batteries that have 10 or 11 bars. That would mean more time and money spent under warranty claims. It was just a buffer statement.

That depends. If you are talking about the 5 year/60K warranty, and you were within a few months of the end of that, they might even give you a 9 bar battery. If you are talking about the $100/month deal, I would expect you to get 11 or 12 bars for the reason you state.

Ray

 

[TomT]

I guess you missed the sarcasm....

Come on you guys, this is precisely why we started working on an aging model last year, and why Stoaty has put so much effort into it.

 

[RegGuheert]

It almost looks like there was a change to the composition of the battery due to high heat in those locales, which could account for some additional loss of capacity.

In fact, some measurements of Li-ion calendar losses indicate that higher temperatures result in drastically faster capacity loss (with a different shape!) than at lower temperatures:

Note the following about the above graph:

- There is NO leveling off of calendar capacity loss. Even at the lowest temperatures it is slightly faster than linear.
- The capacity loss curve has a clear "cliff", EVEN AT ROOM TEMPERATURE.
- While these capacities are measured at a very low-rate discharge (C/33), the paper shows nearly identical calendar capacity loss curves for C/2 discharge rates.
- The researchers felt there were two different mechanisms involved in the fast and slow loss regimes:

The capacity fade at high temperatures demonstrates a two-regime fading pattern. The fading mechanisms in the first regime are mostly Li+ loss and impedance rise, similar as those at low temperatures. The capacity fade in the second regime could be dominated by the severe loss of active carbon.

Of course, the normal disclaimers apply: This measurement is for a different battery chemistry than that used in the LEAF and the operating regime is very different, so the conclusions may not apply to the LEAF.

 

[vegastar]

Lost my first capacity bar today at 57010km (35631 miles). For about a week I'm between 55.20 and 55.25 Ah, so I knew it was imminent. I have P3227 since July. The temperature is way lower than last week (5 TB) so I guess this winter there won't be an uptick incapacity.

 

[nosuchthing]

Lost my first capacity bar today at 35631 miles.

You're right on the money. So, don't grieve and welcome to the one-tooth-missing club.

Now watch your range and your GOM get all weird on you...

 

[surfingslovak]

I guess you missed the sarcasm....

Note the following about the above graph:

- There is NO leveling off of calendar capacity loss. Even at the lowest temperatures it is slightly faster than linear.
- The capacity loss curve has a clear "cliff", EVEN AT ROOM TEMPERATURE.

Right! The good news is that the new capacity warranty has it covered. So stop worrying, will 'ya?

 

[RegGuheert]

Right! The good news is that the new capacity warranty has it covered. So stop worrying, will 'ya?

What's funny is that I didn't think this warranty could ever possibly apply to our car. But someone at Nissan recently CHANGED the in-service date for our demo LEAF from about six months before we purchased the car to a couple of weeks AFTER we purchased the car. I called them to get them to change it back, since it was clearly a mistake and they insisted that the new date was the best one to use. I said, "Great! Change the start date on my extended warranty while you're at it!". Their answer: "O.K." :shock: Anyway, we haven't yet received the new pamphlet on the extended warranty with the new date shown, but hopefully it will come soon. The whole episode was a bit surreal.

Anyway, to make a long story longer, with the recent measurement of about 11% degradation coming about 1.5 years into the newly-adjusted warranty period, combined with superlinear calendar degradations, perhaps, just perhaps, we will get an improved battery just before the end of the warranty expires. Who knows?

 

[dm33]

What's funny is that I didn't think this warranty could ever possibly apply to our car. But someone at Nissan recently CHANGED the in-service date for our demo LEAF from about six months before we purchased the car to a couple of weeks AFTER we purchased the car. I called them to get them to change it back, since it was clearly a mistake and they insisted that the new date was the best one to use.

Why would you want it moved back? Sounds beneficial to you to have it listed as late as possible.

 

[RegGuheert]

Why would you want it moved back? Sounds beneficial to you to have it listed as late as possible.

The main reason I wanted it moved back was that a six-month shift in the in-service date for our LEAF makes it impossible to maintain the battery warranties, which require the battery inspection reports to be at 12-month intervals plus-or-minus 3 months. With a six-month shift following the first inspection, then there was no inspection within the 9-month to 15-month window for the first inspection.

 

[tivollix]

Required inspection date should be based on the in-service date. You may check with with Nissan. But it would be difficult and unfair to require another way.

 

[smkettner]

Right! The good news is that the new capacity warranty has it covered. So stop worrying, will 'ya?

I have gone from worrying about loss of range, then worry about battery price, to worrying about the $100/mo replacement, to worrying if I will get a battery warranty adjustment.
Next I will need to worry about if I will get a warranty 9 bar battery or a new 12 bar battery....
Seems to be never ending worry.

 

[RegGuheert]

Required inspection date should be based on the in-service date. You may check with with Nissan. But it would be difficult and unfair to require another way.

Exactly. The problem is that when we had our battery report done on 29 Sep 2012, our in-service date on the form was 29 Sep 2011. But this September when I tried to schedule the battery report, they told me that I cannot do it until I am in the annual window. They gave me a printout which shows the in-service date is now 29 Mar 2012. In other words, either the first annual battery report will not be within the window or the second one will not be. Both cannot hit the window if the in-service date moved by six months.

It's truly a bizarre situation!

 

[dgpcolorado]

Anyway, to make a long story longer, with the recent measurement of about 11% degradation coming about 1.5 years into the newly-adjusted warranty period, combined with superlinear calendar degradations, perhaps, just perhaps, we will get an improved battery just before the end of the warranty expires. Who knows?

Just my luck that I am at about the same degradation level, 11%, but at 21 months of driving the car I don't figure to hit the magic 66.25% warranty level until ~63 months! Oh well, when first offered I never thought I'd be anywhere close to qualifying for the battery capacity warranty.