Stoaty
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Re: Battery Aging Model

Sun Dec 09, 2012 2:07 pm

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
2011 Leaf with 62,000 miles given to Nephew
2013 Tesla Model S85 with 251 miles rated range at full charge
Leaf Spy Manual
Battery Aging Model Spreadsheet

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evnow
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Re: Battery Aging Model

Sun Dec 09, 2012 5:29 pm

surfingslovak wrote: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.Image
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.
1st Leaf : 2/28/2011 to 5/6/2013
2nd Leaf : 5/4/2013 to 3/21/2017
Volt : 3/25/2017 to 5/25/2018
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evnow
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Re: Battery Aging Model

Sun Dec 09, 2012 5:38 pm

Stoaty wrote:... 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 ...
1st Leaf : 2/28/2011 to 5/6/2013
2nd Leaf : 5/4/2013 to 3/21/2017
Volt : 3/25/2017 to 5/25/2018
Model 3 : 5/10/2018 to ?

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surfingslovak
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Re: Battery Aging Model

Sun Dec 09, 2012 5:57 pm

evnow wrote: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 wrote: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 wrote: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 wrote: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.
Last edited by surfingslovak on Sun Dec 09, 2012 6:28 pm, edited 3 times in total.

Stoaty
Posts: 4490
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Location: West Los Angeles

Re: Battery Aging Model

Sun Dec 09, 2012 6:19 pm

evnow wrote:
Stoaty wrote:... 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).
2011 Leaf with 62,000 miles given to Nephew
2013 Tesla Model S85 with 251 miles rated range at full charge
Leaf Spy Manual
Battery Aging Model Spreadsheet

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TonyWilliams
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Re: Battery Aging Model

Sun Dec 09, 2012 6:20 pm

surfingslovak wrote:.... 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.

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TonyWilliams
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Re: Battery Aging Model

Sun Dec 09, 2012 6:24 pm

Stoaty wrote:...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.

DaveinOlyWA
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Re: Battery Aging Model

Sun Dec 09, 2012 9:39 pm

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
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sparky
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Re: Battery Aging Model

Sun Dec 09, 2012 10:21 pm

Stoaty wrote: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.

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ronwright38
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Leaf Number: 403205
Location: Goodyear, AZ

Re: Battery Aging Model

Fri Dec 28, 2012 12:42 pm

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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