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Re: Battery Aging Model

Posted: Thu Nov 08, 2012 9:28 am
by DaveinOlyWA
RegGuheert wrote:
DaveinOlyWA wrote:this should give us a bit of help in long term range degradation. also HAVE to mention; he is still on his OEM :o 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

Re: Battery Aging Model

Posted: Thu Nov 08, 2012 9:35 am
by TomT
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...

[quote="DaveinOlyWA"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[/quote]

Re: Battery Aging Model

Posted: Sat Dec 08, 2012 5:48 pm
by evnow
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.

Re: Battery Aging Model

Posted: Sat Dec 08, 2012 7:13 pm
by linkim
evnow wrote: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%.

Re: Battery Aging Model

Posted: Sat Dec 08, 2012 8:07 pm
by LEAFfan
ENIAC wrote: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.

Re: Battery Aging Model

Posted: Sat Dec 08, 2012 10:10 pm
by Stoaty
evnow wrote: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.

Re: Battery Aging Model

Posted: Sat Dec 08, 2012 10:55 pm
by DaveEV
Stoaty wrote: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.

Re: Battery Aging Model

Posted: Sun Dec 09, 2012 10:03 am
by evnow
Stoaty wrote: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 ?

Re: Battery Aging Model

Posted: Sun Dec 09, 2012 10:35 am
by Stoaty
evnow wrote: 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. ... nd_Actions" onclick="window.open(this.href);return false;

Re: Battery Aging Model

Posted: Sun Dec 09, 2012 12:03 pm
by surfingslovak
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.Image