Battery Aging Model

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RegGuheert said:
DaveinOlyWA said:
this should give us a bit of help in long term range degradation. also HAVE to mention; he is still on his OEM :eek: tires still has plenty of tread left! :shock:
That's an interesting data point! Can you please tell us what tire pressure he uses? TIA!

i will ask him but guessing its 44 PSI. he states he regularly gets near 100K miles on his tires!

higher pressures means longer life but no real evidence that super high is significantly beneficial
 
Tire longevity is much more dependent on how you drive (almost all straight line as opposed to curves, very smooth as opposed to heavy cornering, braking and acceleration, etc.), on what you drive (smooth concrete, rough concrete, asphalt, etc.), and at what temperature you drive than it is on tire pressure (assuming that the tires are at least inflated to the vehicle manufacturers recommendation). I doubt the difference between 36 psi and 44 psi would account for more than a 5 percent difference in tire life...

 
Since someone asked, I decided to take out my GID meter from storage.

At 80% I get 226. In Aug-Nov 2011, I regularly used to get 231 @ 80%.
At 100% I get 272.

Now, some important notes
- this is the first 100% in several days. So the battery is likely not balanced. I'll charge to 100% for a couple of days and let it rebalance.
- it is about 40 degrees here. I expect higher GID # when the summer returns.
- I used to get anywhere between 276 & 280 at 100% charge when I was monitoring daily (Aug-Nov '11)

Given all this, I think the battery capacity has gone down less than 2% in my case.

Here are my inputs to the model
- 21 months
- 13,377 miles
- 0 hours/day in the Sun
- 0 hours/day @ 100%

Note that the last two numbers are not exactly true. We have continuous uninterrupted Sun for 2 months this summer (almost a record). I regularly used to charge to 100% on weekends earlier.

Yet, the model predicts that my GID # at 100% would be 258 or 8.1% loss. Given that the actual is 3.2% (taking 272 & 281), the model has an error of 153%.

Update 1 : Today after another 100% charge, it shows 274 i.e. 2.5% loss.
 
evnow said:
At 80% I get 226. In Aug-Nov 2011, I regularly used to get 231 @ 80%.
At 100% I get 272.

Just for comparison, I read on the WattsLeft meter the following:

12/3/12: 80% charge - 222 gids (45F outside, LEAF in garage)
11/25/12: 100% charge – 271 gids (50F outside, LEAF in garage). The first 100% charge recorded with the meter was on 10/14 using L1 - 276 gids (57F in San Francisco)

Temperature is the dash reading when data recorded. I drive a
2011 LEAF (19 months old), has about 9000 miles and never had QC and rarely charge at 100%.
 
ENIAC said:
Also, in my experience, the Phoenix valley has a lot of unshaded parking.

How many years of experience do you have here? Because if one is willing to walk sometimes there is almost always (99% of the time) shaded parking to be found. And it isn't just BEV drivers, but I've talked to many ICE drivers that almost always park in shaded spots and don't mind walking the length of the lot.
 
evnow said:
Yet, the model predicts that my GID # at 100% would be 258 or 8.1% loss. Given that the actual is 3.2% (taking 272 & 281), the model has an error of 153%.
You are assuming that Gids are an accurate prediction of actual capacity. Given the known inaccuracies in the readings in Phoenix (where Gids were way too pessimistic in many cases compared to actual capacity loss), I don't think this is a safe assumption. It may be that in very cool environments Gids are overly optimistic. The model is based on Nissan's data. To show that the model is off significantly, one would have to get an accurate measure of actual capacity, either through your own range test, or by having Nissan test to determine the actual capacity loss. One advantage of the 2013 Leafs is that the instrumentation to measure battery capacity should be much better according to Nissan.
 
Stoaty said:
To show that the model is off significantly, one would have to get an accurate measure of actual capacity, either through your own range test, or by having Nissan test to determine the actual capacity loss.
Another way to measure battery pack capacity is to drain the battery to turtle and measure energy from the wall used to charge back up to 100%.

If you are worried about balance, I hypothesize that measuring time/energy to charge from 80% to 100% may provide an indicator of how well balanced the pack happened to be (shorter 80-100% time/energy means the 100% was stopped a bit short), though I don't have any actual data to back this up except for data that shows 80-100% time/energy has varied by up to 20 minutes and 1.1 kWh from the wall across about 10 80-100% charges over the past year.
 
Stoaty said:
You are assuming that Gids are an accurate prediction of actual capacity.
Not really - if you look back at my last year's posts you will see how unreliable I thought GIDs were. I'm just comparing to the GIDs predicted in the model worksheet. If Gids are not accurate, they shouldn't be there in the sheet.

The model is based on Nissan's data. To show that the model is off significantly, one would have to get an accurate measure of actual capacity, either through your own range test, or by having Nissan test to determine the actual capacity loss. One advantage of the 2013 Leafs is that the instrumentation to measure battery capacity should be much better according to Nissan.

I don't know what you mean by the model uses Nissan's data - do you mean actual capacity as measured by Nissan's instruments ? How much data do we have - and for which cities ?
 
evnow said:
Not really - if you look back at my last year's posts you will see how unreliable I thought GIDs were. I'm just comparing to the GIDs predicted in the model worksheet. If Gids are not accurate, they shouldn't be there in the sheet.
You have a point there, but some people may like to compare their Gid reading. Perhaps I should add a caveat in the documentation section. Since I don't have the energy to work on the model further, probably nothing will change.

I don't know what you mean by the model uses Nissan's data - do you mean actual capacity as measured by Nissan's instruments ? How much data do we have - and for which cities ?
I mean the data that TickTock got from the Nissan engineer, which is the only data we have from Nissan:

http://www.mynissanleaf.com/wiki/index.php?title=Battery_Capacity_Loss#Nissan.27s_Responses_and_Actions" onclick="window.open(this.href);return false;
 
Evnow, why don't you go and read up on it, it's all in the Wiki and on the forum. Stoaty should be commended for all the hard work and effort that has gone into the model. In absence of something better from Nissan, which may or may not come, it's the best thing we have to estimate how the battery will do in different conditions.

Yes, Gids are not accurate and should not be relied upon. Our problem is that we don't have much data, and what we have is not very reliable. You probably know this better than anybody. This doesn't mean that significant trends cannot be spotted, and we are not able to predict certain outcomes, such as battery life, in broad strokes.

While your datapoint is certainly appreciated, I would not go as far as claiming that the model is 150% inaccurate. If you combine that with the off-the-cuff remark you made earlier that the battery will only show significant degradation in the deserts, it's becoming apparent that you must have spent close to zero time looking this topic this summer.

If you have a better idea how to approach this or wish to improve the model in a significant way, I'm sure that your contribution is very welcome. I would refrain from taking pot shots and making self-serving remarks however.
1
 
For those who haven't been following the discussion over the last 6 months, I have added the following caveat to the Battery Aging Model section of the Wiki:

Note: While the Battery Aging Model predicts Gids remaining at 100% charge or 80% charge, these values should be taken with a large grain of salt. Gids have been shown to over-predicts capacity loss in Arizona, and may under-predict capacity loss in very cold climates. The only ways to test the model predictions are:

  • Perform a range test like the one done by Tony Williams and crew in Arizona
    Measure the kwh needed from the wall to charge the Leaf from turtle and apply an estimated charging efficiency factor.
    Have Nissan perform a test of battery capacity
 
surfingslovak said:
Evnow, why don't you go and read up on it, it's all in the Wiki and on the forum. Stoaty should be commended for all the hard work and effort that has gone into the model. In absence of something better from Nissan, which may or may not come, it's the best thing we have to estimate how the battery will do in different conditions.

I sure appreciate everyone who has worked on this problem. But that doesn't mean it should not be questioned. Finally, we all have to be reality-based.

While your datapoint is certainly appreciated, I would not go as far as claiming that the model is 150% inaccurate.

I didn't say the model is 150% inaccurate. I said it has a 150% error in what it predicts in terms of GID in my case. Sorry, if you don't like facts.

If you have a better idea how to approach this or wish to improve the model in a significant way, I'm sure that your contribution is very welcome. I would refrain from taking pot shots and making self-serving remarks however.
1
I think we should refrain from "predicting" battery capacity until we have better data. I'm no Nate Silver, but even I know you shouldn't make a model with so little data.
 
Stoaty said:
... may under-predict capacity loss in very cold climates.
Is there a reason you say this ? I don't know what to make of this, esp. given "may".

The only ways to test the model predictions are:

  • Perform a range test like the one done by Tony Williams and crew in Arizona
    Measure the kwh needed from the wall to charge the Leaf from turtle and apply an estimated charging efficiency factor.
    Have Nissan perform a test of battery capacity

Sorry, the first two are just not good enough to figure out small capacity differences (like mine where the model predicts 8%, and I think it is around 2%). I doubt the dealer will test my battery ...
 
evnow said:
Sorry, the first two are just not good enough to figure out small capacity differences (like mine where the model predicts 8%, and I think it is around 2%). I doubt the dealer will test my battery ...
It's always worth asking, I had friends that persisted, and got the number they were looking for. This is just a pure guess, but I would think that your battery could easily be 4-5% down without you noticing. Gids cannot be fully trusted in either cold and hot weather. Be it as it may, we are splitting hairs here. We already know that the battery will do fine in Seattle, but there will be a significant and noticeable hit after the first year in southern climes. And this includes places that are not deserts by any definition: Houston, Dallas, Los Angeles, etc.

evnow said:
I didn't say the model is 150% inaccurate. I said it has a 150% error in what it predicts in terms of GID in my case. Sorry, if you don't like facts.
I do like facts as much as anybody. Unfortunately, we don't have access to a lot of accurate information, as I acknowledged above. What I don't like at all is your attitude, which seems to permeate your recent writing. If I may, I would recommend a little exercise in empathy before penning your next post. You might be surprised at the results.

evnow said:
I think we should refrain from "predicting" battery capacity until we have better data. I'm no Nate Silver, but even I know you shouldn't make a model with so little data.
And that's where we disagree once again. Had you read the posts on the forum from this summer, you would understand how we ended up here, and why we even tried to put something together, given the data we have. You would not be the first or last EV advocate from a cool climate second-guessing the work of others, who might be more affected by battery degradation than you appear to be.

Yes, ideally, Nissan would furnish this data, and there would be more transparency in terms of battery life, and what degradation can be expected based on climatic influences and usage patterns. Although we might get there eventually, it still appears to be long way off. We cannot get even some basic information such as battery replacement costs out of them, which is one the high priority items requested by the owner community.

evnow said:
I sure appreciate everyone who has worked on this problem. But that doesn't mean it should not be questioned. Finally, we all have to be reality-based.
Certainly, and given the community on this forum, you can be certain that things have been approached thoughtfully and were debated at great length before.

While on the topic, let me remind you that you were one of the people claiming that your Leaf was habitually getting 100 miles on a charge in the summer, without actually going the distance. That's not a very scientific approach, which was pointed out to you before, and I don't think we ever agreed on that. We now know that the energy economy gauge cannot be fully trusted either, and most new owners have difficulty driving below the low battery warning. If the 2013 Leaf had improved efficiency and instrumentation, perhaps we will see the membership in the 100-mile club grow.
 
evnow said:
Stoaty said:
... may under-predict capacity loss in very cold climates.
Is there a reason you say this ? I don't know what to make of this, esp. given "may".
Yes, because Nissan's model predicts about a 9% loss in 21 months (and probably 12,500 miles of driving) for Boston, which has a climate quite similar to yours. At best we might expect a 5-6% loss for you since Seattle has a slightly more favorable climate than Boston, and most of the early loss is calendar loss rather than cycling loss. The fact that your Gid meter says you have only lost 2-3% in over a year strongly suggests that the Gid meter may be off in the other direction in Seattle than it is in Phoenix. Same result for DaveinOlympia. However, there is another guy up in Washington with over 50,000 miles whose estimated capacity loss (and also Gid reading) is very close to what the model predicts.

The only ways to test the model predictions are:

  • Perform a range test like the one done by Tony Williams and crew in Arizona
    Measure the kwh needed from the wall to charge the Leaf from turtle and apply an estimated charging efficiency factor.
    Have Nissan perform a test of battery capacity
Sorry, the first two are just not good enough to figure out small capacity differences (like mine where the model predicts 8%, and I think it is around 2%).
Agreed that it is difficult to measure small differences in capacity loss, which reinforces that you don't really know how much capacity you have lost (we know that the Gid meter doesn't give you information that is accurate enough).
 
surfingslovak said:
.... I would think that your battery could easily be 4-5% down without you noticing. The Gids cannot be fully trusted in either cold and hot weather. Be it as it may, we are splitting hairs here....

I do like facts as much as anybody. Unfortunately, we don't have access to a lot of accurate information, as I acknowledged above. What I don't like at all is your attitude, which seems to permeate your recent posts.

I don't know, any more than you, how much loss your particular battery has. Based on the models presented, I would expect it to be closer to that model then your guess. Yes, that would mean the Gids are way off. But, we already know that ambient seasonal temperature changes are affecting the Gid count inverse to reality.

I predict that whatever algorithms were formulated for the Hall effect device that is the basis for Gids works reasonably well at the workshop temperature that they were designed in. Cold and hot seems to throw it for a loop, but not so much that we must throw it out with the bath water. For each of we lowly consumers, I predict that Gids and well done driving tests are the best we have today.

The dealer option to test for "real capapcity" seems at least likely, provided you don't walk in with the not very positive you present here on the subject. Why not try that first, before casually strolling in and denigrating other's hard work?

Maybe then you could do a real world range test and compare all three pieces of data here (range, Gid, dealer measured capapcity). That sounds much more positive.
 
Stoaty said:
...The fact that your Gid meter says you have only lost 2-3% in over a year strongly suggests that the Gid meter may be off in the other direction in Seattle than it is in Phoenix.

I think empirically we already know this. Gid count goes up in winter, when clearly batteries don't get more capapcity when cold. And, the heat of Phienix cobviously had the opposite effect.

That's assuming its marginally correct at 21C room temperature, which I think it is.
 
i have to agree with GID count being no better than a guideline to the actual charge available. I am getting 275 GID occasionally which "on paper" tells me I have lost a minimal amount of range but in reality, I have to say my "true" GID reading is more around 263-265 and this is speculation really but;

I had spent more than a week charging to full and getting GID reading between 263 and 266 and this happened right when two things happened almost simultaneously and that was parking outside and a drop in the temps.

now the weather is not as cold and due to some concern with overnight lows would hit near 30 or less, I went to charging at 120 volts which means the charge is done much later (otherwise i frequently finish charging by 1-2 am) in order to keep the pack warmer and now the GID count has popped back up to 274-275 but its a false reading.

the other thing I started doing is tracking GIDs and how far they drive. this is not an exact science and most of the time i dont even write the numbers down but do see that each GID is "generally" good for .2-.4 miles

but I have observed several instances where a GID is skipped (i.e. goes from 172 to 170) or changes very quickly. This tells me that that GID was probably never there and a "recount" corrected the error.

either way, I think my previous thoughts of "balancing" the pack when I got a unusually low reading was no balancing at all. it was simply a truer reading than what i normally saw

now, the GID count is still affected by temperatures but I think the effect of losing GID in heat is much greater and the effect of gaining GIDs in cold weather is nonexistent unless its to gain back the "heat" loss

i think the GID count is more accurate in the middle but not so much at the very top
 
Stoaty said:
For those who haven't been following the discussion over the last 6 months, I have added the following caveat to the Battery Aging Model section of the Wiki:

Note: While the Battery Aging Model predicts Gids remaining at 100% charge or 80% charge, these values should be taken with a large grain of salt. Gids have been shown to over-predicts capacity loss in Arizona, and may under-predict capacity loss in very cold climates. The only ways to test the model predictions are:

  • Perform a range test like the one done by Tony Williams and crew in Arizona
    Measure the kwh needed from the wall to charge the Leaf from turtle and apply an estimated charging efficiency factor.
    Have Nissan perform a test of battery capacity
Nice work on the battery model Stoaty. I will probably try a range test next month when my LEAF turns 2. My 100% "Gid" numbers track pretty closely with your model but my 80% numbers don't seem to follow at all. I had some reductions when the summer heat hit but even though the 100% are reduced (currently around 265), the 80% stay pretty close to 225-231. In fact the last couple of 80% charges have been 231s. Perhaps I'm just an outlier on the 80% Gids.
 
I have 14,000 Miles and I lost one Bar and the miles when charged is any way from 88 mile to 95 mile and when I drive for 5 or 6 miles it drops to 80 , then after 25 miles it drops to 55 miles and some time i just make back home to charge it . what can be done to get the battery pack fixed as when I picked up the car it was in the showroom for 6 months as a demo and think that's why the batteries did not hold the charge and i live in Arizona . ;)
 
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