Capacity Loss on 2011-2012 LEAFs

I think the CC trick only works if the 100% voltage is lower than 394V. As your today charge yelded 270gids@394V there was no room for extra electrons to sneak in.

The charger goes into a CV (Constant Voltage) mode, and will not go above 394v. But usually holding at this voltage for a longer time will allow equalization and as much charge as possible at 4.1vpc. Of course, You'll lose charge if your climate control pulls more than your charger can provide. So if you are pulling over about 3.1kW on full 240v level II, you'll lose some charge. Letting it continue will usually get it back, as the Leaf will come down (or up) to temperature and CC draw will reduce. A hot car in the sun may never come down in time though.

-Phil

Lost my top bar this morning after charging to 100% early this morning. 11,383 miles and one year one month and five days in.

Sorry, looks like you number 9 reporting here. Please provide more details about your driving style efficiency and about charging ( 80 or 100) and storage especially during summer (shade or sun). Wonder if you leased or bought?

I'm not sure how relevant driving, charging and storage habits really are at this point. We seem to have heard from people with a wide variety of habits. I don't see his experience posted on this forum, but I know of another Phoenix area Leaf owner who lost a bar this month after about 16,000 miles... despite almost always charging to 80% in an air-conditioned garage, having covered parking at work, almost never fast charging (about three times in over a year), and certainly never running the battery pack dead. This guy was THE gold standard for vehicle care by Nissan's standards, and yet has roughly 15-20% loss as of this month...

opossum said:

I'm not sure how relevant driving, charging and storage habits really are at this point. We seem to have heard from people with a wide variety of habits. I don't see his experience posted on this forum, but I know of another Phoenix area Leaf owner who lost a bar this month after about 16,000 miles... despite almost always charging to 80% in an air-conditioned garage, having covered parking at work, almost never fast charging (about three times in over a year), and certainly never running the battery pack dead. This guy was THE gold standard for vehicle care by Nissan's standards, and yet has roughly 15-20% loss as of this month...

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As more info is coming from 11 bars people it appears that unfortunately you are right.

My garage isn't air conditioned, but I got five stars across the board on my 1-year mandatory checkup so I am apparently not doing anything that Nissan anticipated would hurt battery life.

I think that we have fairly conclusively determined at this point that the portion of the battery report that we get to see is of little value and is very rudimentary at best... The real data goes to Nissan and is for their eyes only...

TickTock said:

My garage isn't air conditioned, but I got five stars across the board on my 1-year mandatory checkup so I am apparently not doing anything that Nissan anticipated would hurt battery life.

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TomT said:

I think that we have fairly conclusively determined at this point that the portion of the battery report that we get to see is of little value and is very rudimentary at best... The real data goes to Nissan and is for their eyes only...

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Yes, but that generic report will be good evidence that we did not cause the degradation and will hopefully keep Nissan from slipping out of this unscathed by claiming that certain owners did this to their own batteries.

I'm 80% charge most days, maybe full once a week if that. I've fast charged about a dozen times. I do park in the sun during the days, but the car is parked in a garage at night so it does have a chance to modestly cool down at night.

opossum said:

I'm not sure how relevant driving, charging and storage habits really are at this point. We seem to have heard from people with a wide variety of habits. I don't see his experience posted on this forum, but I know of another Phoenix area Leaf owner who lost a bar this month after about 16,000 miles... despite almost always charging to 80% in an air-conditioned garage, having covered parking at work, almost never fast charging (about three times in over a year), and certainly never running the battery pack dead. This guy was THE gold standard for vehicle care by Nissan's standards, and yet has roughly 15-20% loss as of this month...

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+1! I whole heartily agree that it has nothing to do with charging (QC included), car color, or habits. Again, just recently, one of the ECOtality techs told me that he was told that drivers in the Phoenix area (not sure if Tucson is included) would experience a loss of a capacity bar every year or every 15K miles. Some people on here seem to despise these 'techs', but this sure sounds valid to me.

LEAFfan said:

opossum said:

I'm not sure how relevant driving, charging and storage habits really are at this point. We seem to have heard from people with a wide variety of habits. I don't see his experience posted on this forum, but I know of another Phoenix area Leaf owner who lost a bar this month after about 16,000 miles... despite almost always charging to 80% in an air-conditioned garage, having covered parking at work, almost never fast charging (about three times in over a year), and certainly never running the battery pack dead. This guy was THE gold standard for vehicle care by Nissan's standards, and yet has roughly 15-20% loss as of this month...

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+1! I whole heartily agree that it has nothing to do with charging (QC included), car color, or habits. Again, just recently, one of the ECOtality techs told me that he was told that drivers in the Phoenix area (not sure if Tucson is included) would experience a loss of a capacity bar every year or every 15K miles. Some people on here seem to despise these 'techs', but this sure sounds valid to me.

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Interesting, looks like we'll find out next year. Here is a complementary observation. The shop manual tells us that the first capacity bar corresponds to 15% battery capacity. The second bar is only 6.25%. The ratio of the two is: 6.25/15 = 0.4167. If your tech is right, this ratio would suggest that battery degradation growing with square root of time. The third capacity bar should take 1 1/2 years to turn off, instead of just one. The fourth bar two years, etc.

He said one lost bar per year, so that's 15% loss the first year, 6% more the 2nd year (21%), then another 6% the third year, etc. He knows the bars aren't linear.

opossum said:

I'm not sure how relevant driving, charging and storage habits really are at this point.

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I agree that they seem to have little impact in hot climates like Phoenix where temperature effects dominated. That said, I don't think we should extrapolate that to the entire LEAF fleet, since degradation due to heat may not dominated in cooler areas.

LEAFfan said:

Again, just recently, one of the ECOtality techs told me that he was told that drivers in the Phoenix area (not sure if Tucson is included) would experience a loss of a capacity bar every year or every 15K miles. Some people on here seem to despise these 'techs', but this sure sounds valid to me.

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At first blush, that prediction seems unrealistic to me. But on further thought, I must admit that I have never seen a battery capacity degradation curve that started off with a 15% drop in year one. Most curves show the battery losing a lower and lower percentage of capacity each year and eventually leveling off into a more linear region. I suppose it's possible the big drops seen in Phoenix will be experienced by others over some larger number of years and they are now in the more linear portion of the curve. Even it that is so, 6.25%/year is a big number in my book.

RegGuheert said:

LEAFfan said:

Some people on here seem to despise these 'techs', but this sure sounds valid to me.

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At first blush, that prediction seems unrealistic to me. But on further thought, I must admit that I have never seen a battery capacity degradation curve that started off with a 15% drop in year one. Most curves show the battery losing a lower and lower percentage of capacity each year and eventually leveling off into a more linear region. I suppose it's possible the big drops seen in Phoenix will be experienced by others over some larger number of years and they are now in the more linear portion of the curve. Even it that is so, 6.25%/year is a big number in my book.

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+1

Additionally, and not to take away from LEAFfan, the ECOtality techs he keeps referring to seem to have voiced fair share of dubious information in the past. Personally, I don't find the statement that it will be one bar every year convincing or plausible.

has anyone in Phoenix kept their pack below 80% on a regular basis? Just because we are seeing premature capacity loss from folks in the 80% and 100% club I don't think we should assume that charging habits make no difference. It would be very interesting to get the stats on someone who does not plug in every day or otherwise keeps the pack closer to 50% and does things like using an end timer. **IF** the cladding activity curve (assuming that is what is causing this deterioration) is something like exponential at some interval over 50% and multiplied additionally by high spike or average temp, then it would reason that cycling the battery closer to 50% could improve things substantially, presuming these Li cells follow a similar curve to others that have been tested. I'm in a much cooler climate but have decided anyway that since much of my driving is just a few bars at a time, that I'm going to cycle closer to the middle of the pack with the hopes of extra long life... the L2 network is starting to look more valuable for shallow cycling. Doing this does add some tedium since I now have to look ahead to top up before an unusual amount of driving is to occur. I figure though, that since the car sits idle most of it's life, the idle SOC hours rack up pretty quickly and keeping the car mostly at a low SOC for the bulk of it's idle hours may improve things quite a bit, perhaps even more so in hot climates. I wonder if 80% isn't actually closer to 100% in terms of deterioration in hot climates... I'm still thinking there should be red at either end of the sock range, yellow inside of that and green being close to the middle to encourage cycling in the middle.

LEAFfan said:

He said one lost bar per year, so that's 15% loss the first year, 6% more the 2nd year (21%), then another 6% the third year, etc. He knows the bars aren't linear.

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It sure doesn't sound like it. I suspect this is speculative. It's unlikely the curve would start out high then have a reduction in loss as time goes on with the same conditions.

I suspect the curve will be largely linear, Nissan only essentially made the first bar equal to 2 before loss shows, probably to stem off panic.

Since Ecotality's engineering in their own products speaks for itself, I'd be hard-pressed to take anything their engineers (or worse, a lowly "tech") say as fact. The Ecotality "tech" that showed up at my place was maybe qualified to be an Electrician, but definitely know nothing about EV's.

-Phil

RegGuheert said:

I have never seen a battery capacity degradation curve that started off with a 15% drop in year one. Most curves show the battery losing a lower and lower percentage of capacity each year and eventually leveling off into a more linear region.

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Ingineer said:

I suspect the curve will be largely linear, Nissan only essentially made the first bar equal to 2 before loss shows, probably to stem off panic.

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I have anticipated something linear as well, and I did not see a 15% drop coming in the first year. The only explanation I would have is that calendar life loss seems to be the dominant force. While cycling losses seem to increase linearly with time and the number of cycles, I believe that calendar life degradation increases with the square root of time.

If that's the case, the second year calendar life loss will be roughly 40% of the first one, the third year 22%, the fourth year 15%, etc. It's conceivable that if calendar life losses keep getting smaller with the age of the vehicle, cycling losses will become the dominant force at some point in the future, and the decline will be roughly linear then.

For what it's worth, here is the projected degradation of the Panasonic cells similar to the ones Tesla is allegedly using in the Model S:


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The graph shows cycle fade, which, from the model studies, would be expected to be more linear.

I would agree that, in warm climates, storage (calendar) capacity fade should dominate, especially since most of our cars sit idle around 90-95% of the time. Being proportional to t^1/2, we should see the biggest loss the first year with smaller and smaller losses in subsequent years. Just extrapolating from a 15% first year loss, would give around 21% loss at the end of the second year, 26% loss at the end of the third and 30% loss at the end of the fourth.

I would hate to think the losses Phoenix residents are seeing are cycle losses. A nearly linear loss curve with a 15% drop in the first year would be a disaster.

Weatherman said:

The graph shows cycle fade, which, from the model studies, would be expected to be more linear.

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Correct. Note the mildly elevated temperature however. 25C or 77F would suggest that they wanted to either accelerate aging or tried to simulate harsher conditions. The NREL reports we looked earlier at determined that constant 28C or 82.4F was causing about the same level of calendar loss for their NCA cells as the climate in Phoenix would. Another thing worth noting is that the test cycle is more agressive as well: 2.5 to 4.2V compared with Leaf's 3.2 to 4.1V (turtle to full charge).

I've included the Panasonic chart, because it seems to imply a 7% loss in the first year. That's based off the rated 2.95 Ah capacity, and not the 3.1 Ah maximum. I eyeballed the remaining capacity at 2.75 Ah after 100 cycles. It's a bit arbitrary, but this number of cycles would be about 10K miles or 1 year on the Leaf.