Discuss data from the LEAF Battery app, and Comparisons

[Weatherman]

And, in spite of all these little details, the current, Stoaty model is still performing pretty well.

In fact, in my LEAF's case, in spite of all the complaining I do about it , the battery is, actually, doing a bit better than the model predicts.

 

[surfingslovak]

And, in spite of all these little details, the current, Stoaty model is still performing pretty well.

Yes, indeed! Not to take away from all the work that has gone into it, this model is based on very broad strokes and assumptions, and I'm sure that it could be refined further if needed.

 

[GregH]

It seems odd to me that people are discussing the vagaries of firmware known to give an inaccurate reading of the Leaf battery capacity. Why not get the P3227 update (includes compatibility fixes for some EVSE) and discuss the more accurate readings?

Good point..

 

[RegGuheert]

It seems odd to me that people are discussing the vagaries of firmware known to give an inaccurate reading of the Leaf battery capacity.

Known? Nissan has said it is more accurate, but beyond that, do we have any evidence that it is true?

I will point out that at one point before any updates were announced, Andy Palmer stated that the capacity meter was always pessimistic. Then when they announced the new firmware, they claimed that it changed the accuracy from +/-10% to +0%/-4% (IIRC). Those two statements are mutually exclusive, so both cannot be true.

Why not get the P3227 update (includes compatibility fixes for some EVSE) and discuss the more accurate readings?

There is no benefit in that update for me so I'm not going to make a special trip for it. Next time the LEAF is in for something else, I will get it updated.

 

[RegGuheert]

With all due respect, I don't think that this matters very much.

I will say that you have promoted the idea that the battery temperature only gets a few degrees above the ambient temperature while driving, even at high speeds. The point is that the design ensures that while the readings at the temperature sensors will not get more than a few degrees above ambient while driving, the battery chemistry always gets above that level and may get significantly above that point. We don't know for sure.

I will also say that in hot climates like Phoenix or Florida, various changes in how you baby the LEAF may only impact the life of the car by a few months. In that case, it is hardly worth doing those things or even thinking about it. That is also so for those who have leased their LEAFs. But many here may be able to achieve battery life of more than a decade with our LEAFs. In these situations, we may be able to extend the usable life of our batteries by years by how we treat the battery. In other words, an extra 10% or 20% of life is a much bigger deal if your battery is going to last a long time. So please don't begrudge those of us trying to preserve our batteries as much as possible. I like to think that one of the reasons people purchase EVs to try to reduce our footprint on this Earth. Personally, I don't embrace the concept of "ride it hard and put it away wet", with all that implies. To each his own.

The car will spend the majority of its life just sitting, not charging and not driving.

Consider this: Regardless of whether or not the LEAF is driving, charging or just sitting, the temperature of the Inner Cells will nearly always be above the readout of the sensors. Sometimes, it will be significantly higher. In other words, our batteries are almost always hotter than the sensors say. This is an unfortunate result of the fact that the heat is dissipated from within the cells.

While what you mentioned is good to keep in mind and to consider, I don't believe that it will turn out to be very significant. I would also point out that we had another rather academic debate about the error of the voltage sensor last year. While these discussions can be entertaining, educational and perhaps even illuminating, it would be good if they did not shift away focus away from more significant factors and observations.

I think many here are lulled into thinking that they are not hurting their batteries by observations such as "the temperature of the battery never gets more than a few degrees above ambient no matter what I do." While that may be true for the sensor readings on a new battery while driving, the truth is that there is a bit more to the story than such statements imply. The fact is that we do not know how much higher the rise is within the cells. I believe it is at least twice the rise we see at the probe, but I also think it is possible that it could be as much as 5X the rise we can see. As our batteries degrade, things like electrical and thermal resistances will get higher, which will make matters worse. That could be part of the reason why calendar degradation tends to be linear rather than the idealized results predicted by many of the models out there. (And that is not a dig for Stoaty! I know the equations he chose for calendar losses come from many papers out there.)

 

[Stoaty]

As our batteries degrade, things like electrical and thermal resistances will get higher, which will make matters worse. That could be part of the reason why calendar degradation tends to be linear rather than the idealized results predicted by many of the models out there. (And that is not a dig for Stoaty! I know the equations he chose for calendar losses come from many papers out there.)

Stoaty hopes the calendar losses follow the square root of time... not because he is invested in his model though, because he is invested in his Leaf.

 

[TomT]

In a perfect world, that might be true. But as one utilizes more and more charge/discharge cycles (a full charge and discharge is considered to be one cycle) to make up for reduced capacity, the square law may be distorted...

Stoaty hopes the calendar losses follow the square root of time... not because he is invested in his model though, because he is invested in his Leaf.

 

[RegGuheert]

Stoaty hopes the calendar losses follow the square root of time... not because he is invested in his model though, because he is invested in his Leaf.

Believe me, so does Reg!

 

[surfingslovak]

I will say that you have promoted the idea that the battery temperature only gets a few degrees above the ambient temperature while driving, even at high speeds. The point is that the design ensures that while the readings at the temperature sensors will not get more than a few degrees above ambient while driving, the battery chemistry always gets above that level and may get significantly above that point. We don't know for sure.

Yes, guilty as charged. Below is an example of a statement I made in this regard last year. This was before we had the ability to easily read the temperature sensors. That said, let's recall that the model operates on a relative and not an absolute basis. If the cell surface is on average X degrees above ambient and the cell core is Y degrees above ambient, we will see similar rise above ambient in all environments. The difference between absolute cell temperature in different locales can still be calculated relatively safely and accurately from the ambient temperature.

I would expect battery temps to follow the ambient fairly closely. Vehicle operation can add about 5 degrees, and level 2 charging about 10 degrees on average. And this waste heat can take several hours to dissipate.

The effects of solar loading and radiant heat from the pavement are unclear, and difficult to estimate without an accurate temperature gauge. Judging from owner reports, I would be surprised if these two factors pushed the pack more than 15 degrees above ambient. It's likely a delta of 5 to 10 degrees, perhaps even less than that.

I will also say that in hot climates like Phoenix or Florida, various changes in how you baby the LEAF may only impact the life of the car by a few months. In that case, it is hardly worth doing those things or even thinking about it. That is also so for those who have leased their LEAFs.

What do you mean by the term "baby the LEAF" exactly? If it's in reference to careful cycling of the battery, then I agree, that won't matter much. It's relatively well understood that calendar loss has a dominant effect in those climates.

But many here may be able to achieve battery life of more than a decade with our LEAFs. In these situations, we may be able to extend the usable life of our batteries by years by how we treat the battery. In other words, an extra 10% or 20% of life is a much bigger deal if your battery is going to last a long time. So please don't begrudge those of us trying to preserve our batteries as much as possible.

I'm sorry, but I'm not aware of taking this stance? Can you clarify? I have spent vast amount of time and effort trying to understand what drives battery capacity loss in the LEAF. This started out with cross-posting the Tesla battery care guide from Dan Myggen in early 2011. I wish every LEAF owner a long and happy ownership experience. One of the remedies suggested early on was a capacity warranty, and later a battery lease, which helps allay concerns about battery capacity. I'm sorry if the ultimate outcome is not be what was hoped for. I most certainly don't begrudge any battery capacity conservation efforts, and I'm sorry if I ever gave you that impression.

I like to think that one of the reasons people purchase EVs to try to reduce our footprint on this Earth. Personally, I don't embrace the concept of "ride it hard and put it away wet", with all that implies. To each his own.

Neither do I, and I babied my LEAF and did not own a car for several years prior to that for this reason. I purposefully waited for an EV.

Consider this: Regardless of whether or not the LEAF is driving, charging or just sitting, the temperature of the Inner Cells will nearly always be above the readout of the sensors. Sometimes, it will be significantly higher. In other words, our batteries are almost always hotter than the sensors say. This is an unfortunate result of the fact that the heat is dissipated from within the cells.

Yes, I certainly understand, but yet I don't see how that matters. The model Stoaty has refined is based on relative performance in different locales. While there will be some differences, if we assume the same average usage pattern in different parts of the country, we can also assume approximately the same heating pattern in the cell core and on the cell surface. The Arrhenius equation offers an effective way to estimate the speed of a chemical reaction based on a temperature difference. We don't need the absolute temperature to asses the relative speed of calendar aging in two different locations.

I think many here are lulled into thinking that they are not hurting their batteries by observations such as "the temperature of the battery never gets more than a few degrees above ambient no matter what I do." While that may be true for the sensor readings on a new battery while driving, the truth is that there is a bit more to the story than such statements imply. The fact is that we do not know how much higher the rise is within the cells. I believe it is at least twice the rise we see at the probe, but I also think it is possible that it could be as much as 5X the rise we can see.

The reason why I personally placed so much focus on ambient temperature and the local climate is simple: the early analysis I performed on 50 vehicles distributed across different geographies (including Spain and Norway) indicated 70% correlation to the average annual temperature at the place of residence. I found that unexpected and absolutely stunning. Mind you, I tried to consider other factors, such as mileage, 80% and 100% charging, QC frequency, the car color, etc. While more accurate data is available now, I would be surprised if other factors (aside from mileage) were shown to contribute more than a few percentage points to the overall capacity loss.

As our batteries degrade, things like electrical and thermal resistances will get higher, which will make matters worse. That could be part of the reason why calendar degradation tends to be linear rather than the idealized results predicted by many of the models out there. (And that is not a dig for Stoaty! I know the equations he chose for calendar losses come from many papers out there.)

Yes, absolutely. The internal capacity will definitely rise, but I wouldn't want to theorize how well this pack will age. Given Nissan's long history with this chemistry, it's probably safe to assume that a ten year life is possible. The only question is how much capacity will remain and if the owner will have a good use case for the vehicle. I think the conservative approach in terms of cycling, charging, storage and operation is well understood by now. What we do not know is the relative gain from these efforts. If I argue that the long-term average temperature will likely prove to be the most dominant factor, that's more out of an academic interest. Please don't construe it as an effort to undermine the development of a better understanding of these batteries. I wasn't as disciplined as Stoaty, but what I did with my LEAF and the way I drove it speaks a clear language, I believe.

 

[mwalsh]

6/22: AHr=54.07 CAP=81.61%
6/24: AHr=54.01 CAP=81.52%
6/25: AHr=54.12 CAP=81.68%
7/11: AHr=53.16 CAP=80.23%
7/12: AHr=53.30 CAP=80.45% Hlth=76.57%
8/26: AHr=52.54 CAP=79.30% Hlth=75.16%
9/11: AHr=51.49 CAP=78.49% Hlth=73.22%
10/2: AHr=51.81 CAP=78.98% Hlth=73.82%
10/8: AHr=51.58 CAP=78.63% Hlth=73.39%
10/23: AHr=52.12 CAP=79.51% Hlth=74.46%

11/5: AHr=52.68 CAP=80.31% Hlth=75.43%

 

[Weatherman]

No reversal in trend, here:

July 11th: 57.45 Ahr
Aug 12th: 56.30 Ahr
Sept 10th: 55.46 Ahr
Oct 23rd: 54.61 Ahr
Nov 4th: 54.26 Ahr


Battery temps have backed off into the lower 80s, but capacity is still falling at a very steady pace.

Curiously enough, I started to see five temperature bars when the battery temp was around 78F. A good demonstration of how the threshold between the 5th and 6th temp bar creeps up as the battery capacity goes down.

 

[garygid]

Curious that the higher Temperature Bars break-
points are programmed to creep up as the battery
capacity diminishes.

Is this trying to tell us that...
the Temperature bands are warning zones, and
that a "well-aged" battery is more tolerant of
higher temperatures, but just as wary of lower
temperatures?

 

[JeremyW]

Is this trying to tell us that...
the Temperature bands are warning zones, and
that a "well-aged" battery is more tolerant of
higher temperatures, but just as wary of lower
temperatures?

More likely the internal resistance goes up as the pack ages, so the gauge is tuned to hide the higher amount of "self heating."

 

[RegGuheert]

Reported capacity is not moving around much (pre-P3227), as I expect. I have added SOC, average Vbat and maximum Temp to my table for information purposes:

09/28: Odo=13,877 AHr=59.18 CAP=90.21% Hlth=87.89% SOC=90.2% Vbat=4.097 Temp=77.7F
10/22: Odo=14,515 AHr=59.39 CAP=90.53% Hlth=88.31% SOC=33.1% Vbat=3.838 Temp=63.1F
10/24: Odo=14,515 AHr=59.39 CAP=90.53% Hlth=88.31% SOC=94.0% Vbat=4.100 Temp=51.6F
10/25: Odo=14,595 AHr=59.47 CAP=90.66% Hlth=88.46% SOC=17.9% Vbat=3.735 Temp=53.0F
10/27: Odo=14,636 AHr=59.36 CAP=90.49% Hlth=88.09% SOC=39.2% Vbat=3.843 Temp=53.8F
10/30: Odo=14,705 AHr=59.18 CAP=90.21% Hlth=87.91% SOC=35.4% Vbat=3.850 Temp=62.9F
11/07: Odo=14,951 AHr=59.35 CAP=90.47% Hlth=88.50% SOC=43.4% Vbat=3.846 Temp=64.9F

The last two readings seem to indicate just how far off the SOC meter can be. With the max (and also average) battery temperature sensor readings within 2F and a lower average Vbat, the SOC reported on 11/07 was 8% higher than was reported on 10/30.

I will also note that the ambient temperature yesterday (11/07) was 48F when that reading was taken. As such, the temperature reading at the highest sensor was 17F higher than ambient. The battery had been charged to full about six hours prior and the car had been driven about 50 miles total. Undoubtedly the temperature within the battery chemistry was above 70F during that drive.

 

[mwalsh]

6/22: AHr=54.07 CAP=81.61%
6/24: AHr=54.01 CAP=81.52%
6/25: AHr=54.12 CAP=81.68%
7/11: AHr=53.16 CAP=80.23%
7/12: AHr=53.30 CAP=80.45% Hlth=76.57%
8/26: AHr=52.54 CAP=79.30% Hlth=75.16%
9/11: AHr=51.49 CAP=78.49% Hlth=73.22%
10/2: AHr=51.81 CAP=78.98% Hlth=73.82%
10/8: AHr=51.58 CAP=78.63% Hlth=73.39%
10/23: AHr=52.12 CAP=79.51% Hlth=74.46%
11/5: AHr=52.68 CAP=80.31% Hlth=75.43%

11/12: AHr=52.47 CAP=79.98% Hlth=74.80%

Oh, dear...on the march down again.

 

[TomT]

Same here!

Oh, dear...on the march down again.

 

[mwalsh]

6/22: AHr=54.07 CAP=81.61%
6/24: AHr=54.01 CAP=81.52%
6/25: AHr=54.12 CAP=81.68%
7/11: AHr=53.16 CAP=80.23%
7/12: AHr=53.30 CAP=80.45% Hlth=76.57%
8/26: AHr=52.54 CAP=79.30% Hlth=75.16%
9/11: AHr=51.49 CAP=78.49% Hlth=73.22%
10/2: AHr=51.81 CAP=78.98% Hlth=73.82%
10/8: AHr=51.58 CAP=78.63% Hlth=73.39%
10/23: AHr=52.12 CAP=79.51% Hlth=74.46%
11/5: AHr=52.68 CAP=80.31% Hlth=75.43%
11/12: AHr=52.47 CAP=79.98% Hlth=74.80%

11/22: AHr=52.74 CAP=80.40% Hlth=75.53% (or whatever we're calling Hlth these days).

 

[vrwl]

Still have 12 bars, despite the lower than average (for one bar losers) AHr readings:

8600 miles/12 Bars/4.6kWh/229 GID at 100%/193 GID at 80%/54.37Ahr/82% CAP/67.17% Hlth

 

[DaveEV]

Ah decline seems to have leveled off the last 3 weeks for me.

Mid Nov Data:
23.5k mi / 11 bars
54.7 Ah / SOH 83% / Hx 68.24%
229/192 GIDs

 

[gsleaf]

I tested my Leaf (leased in August 2012) last week after picking up an Android phone... I was surprised I've lost as much capacity as I have considering I'm in Portland, OR.

12.5k mi / 58.5 Ah / SOH 89% / Hx 77.64%

Edit: corrected the date of the lease from 2013 to 2012.