Stoaty's Battery Degradation spreadsheet now for prospects!

[nogajim]

My predicted loss over 2.55 years in Atlanta was 15.74, but my actual is 18.52. I am not sure of any one thing that might cause the difference. My Ahr, mileage and 80% GIDS were collected today. I estimated my days in the sun as 3. In the summer, it is mostly in my garage, the rest of the year it parks outside with partial shade.

Have you had the P3227 update? The spreadsheet was calibrated with post-P3227 data and is not expected to be valid for those who don't have the update. If you have had the update, please enter the requested information in the thread "Tuning the Battery Aging Model" (unless you already did and I just forgot). I need more data from hotter climates for further tuning.

Had the update in June. Posted to the Tuning thread just now (don't think I did before). Thanks again!

 

[Stoaty]

I have added a column to the input tab of the public spreadsheet that shows the available cities sorted by state or country first, and then by city name. This should make it easier to determine if there is a nearby city with a similar climate in your state (or country). See public spreadsheet here:

https://docs.google.com/spreadsheet/ccc?key=0AqhUVOciAXVhdEFId2ppVEViZmd0ckJxME95N0U4SUE&usp=sharing" onclick="window.open(this.href);return false;

 

[edatoakrun]

="Stoaty"
Testing the battery aging model against the measured loss in the study referenced by Ed, and assuming Phoenix, 4 miles per kwh, no solar loading, and 30,000 miles in one year gives:

Predicted Capacity Loss - 22%

Actual Capacity Loss (after 9 months calendar aging and 30,000 miles) -14%

So the question is, "Would a 9 month old Leaf sitting around for 3 months in Phoenix during a hot summer lose 8% battery capacity?" It wouldn't surprise me if it would lose that much, as calendar capacity loss is greatest in the first year, and in high ambient temperatures.

Bottom line: while not directly comparable, the Battery Aging Model would likely not be far off if the test Leaf sat through a hot Phoenix summer before doing the capacity loss measurement.

40,000 mile capacity test results after ~ one year, as reported here:


http://avt.inl.gov/pdf/energystorage/DCFC_Study_FactSheet_40k.pdf" onclick="window.open(this.href);return false;

Looks like the L2 cars have lost ~22% capacity after 40k miles, rather than the same 22% (14% + 8%) after 30,000 miles, as you speculated.

So, IMO, the actual capacity results reported indicate the model projection you made above seems to have overestimated capacity loss by ~33%, per mile driven and recharge cycle.

BTW, as the charge site photo indicates, I also don't think your assumption of "no solar loading" is correct, which indicates an even greater rate of overestimation of capacity loss in the model.

 

[ksnogas2112]

I can't believe I missed this in Oct. The original spreadsheet was awesome but this is insane. I'm actually envious of the genius involved in figuring this out. And for the record, it looks pretty darn accurate for my battery without having a better way to measure than the dash at this time.

 

[Stoaty]

Looks like the L2 cars have lost ~22% capacity after 40k miles, rather than the same 22% (14% + 8%) after 30,000 miles, as you speculated.

So, IMO, the actual capacity results reported indicate the model projection you made above seems to have overestimated capacity loss by ~33%, per mile driven and recharge cycle.

BTW, as the charge site photo indicates, I also don't think your assumption of "no solar loading" is correct, which indicates an even greater rate of overestimation of capacity loss in the model.

We don't have enough info to be sure, but I would say the spreadsheet is pretty accurate at 40,000 miles and one year: 25.28% estimated for Phoenix vs 22% actual measured. It may be that the solar loading component isn't accurate. Since we don't have many data points for Phoenix to calibrate the model (1 to be exact) and don't know the conditions the cars were stored in and how they were driven, we can't make a valid comparison. However, note that for the one data point we have for Phoenix (TickTock) the model under predicts the amount of loss slightly (27.73% predicted loss, 29.52% actual). Also note that we set the capacity of a new battery at 66.25 Ah, while there is some evidence that a lower number might be the true number (and would make the predictions closer for Phoenix). Also, if the battery actually has more energy than the Gid meter says it does, that isn't of any help to the user since you can't drive past Turtle.

 

[absurdo]

Hello,

Newbie here and am trying to interpret this. Our 2012 SL leaf started to show some signs of degradation. We rarely charge it to 100%- less than once a month. After reading through this forum I got myself a wifi elm327 and got these readings using leaf stat v1.2 on an ipad mini

2012 SL Leaf - 19820 miles
235 GiD's 18.21 kWh
93.75% SOC
84.89% capacity (SOH)
82.13% HX 56.25 Ahr
84.7 F temperature

I tried plugging these into Marty's spreadsheet for San Jose, CA , assuming date of manufacture 1/2/2012 and date of delivery 3/27/2012 and 4 days of sun and am still trying to make sense of whether my numbers make sense.

Can somebody look at these and see if we are seeing any unusual degradation. Any tips to maintain the battery better and sustain warranty?

 

[Stoaty]

Can somebody look at these and see if we are seeing any unusual degradation. Any tips to maintain the battery better and sustain warranty?

Data is incomplete, need your estimated lifetime average efficiency (miles per kwh). That said, assuming an average driving efficiency of 4.0 miles/kwh the spreadsheet gives the following:

Predicted Capacity Loss - 14.52%
Actual Capacity Loss - 15.09%

So yeah, it looks like your Leaf is following the expected rate of degradation. Predicted End of Life (take with a very large grain of salt, of course) with 30% capacity loss (70% capacity retained) is 7.5 years total (5.15 years remaining) and mileage of 63,000 (assuming the same number of miles per year).

 

[mkjayakumar]

There is a comment on the top that says, this tool is not valid for 2013 and later models. Bummer..

 

[KJD]

There is a comment on the top that says, this tool is not valid for 2013 and later models. Bummer..

Why would 2013 be any different than 2012 ?

 

[Stoaty]

There is a comment on the top that says, this tool is not valid for 2013 and later models. Bummer..

Why would 2013 be any different than 2012 ?

Because there were changes to the battery chemistry, hopefully for the better. Later model years would hopefully do at least as well as the earlier models. Of course, having only 100% charge available (not sure what year that went into effect) could make the longevity somewhat worse. Model was derived/tested with the 2011-2012 model years. My guess is that the Lizard battery in 2015 models will do a lot better in climates like Los Angeles and hotter.

 

[dhanson865]

http://www.mynissanleaf.com/viewtopic.php?f=30&p=425925#p425925" onclick="window.open(this.href);return false;

Just thought I'd give you a heads up that I'm invoking the spreadsheet in a degradation discussion.

 

[thankyouOB]

i changed the values and entered mine, but HOW do i get it to digest my entries and give me the predictiosn?

i may be too unfamiliar with such an excel worksheet that yields "view in preview."

 

[dhanson865]

i changed the values and entered mine, but HOW do i get it to digest my entries and give me the predictiosn?

i may be too unfamiliar with such an excel worksheet that yields "view in preview."

I'm afraid you or someone else broke the spreadsheet today.

It appears someone copied a city,state to the B2 field from the list at the right.

There used to be a drop down menu in field B2 that let you choose the city, state.

I restored it to a copy from yesterday and it works again now. Just be sure the city state field is a yellow drop down, do NOT copy and paste the blue fields on top of the yellow (not saying you did, but someone did).

Once you fill in all the yellow fields on the first tab, click on the prediction tab.

 

[thankyouOB]

my bad.
very sorry about that.

I entered the totals and am now trying to understand what I am seeing.
How do I translate what I see to understand changes to range?

But first two pressing questions:
-In terms of "days in the sun"--what do I enter if my parking spot is in the sun part of each day, then the shadow moves over the car around midday? 3.5 or 4?

and

-How do I adjust the mileage vector as my commute (and so yearly mileage) is now about 3.5k a year sted of 11k a year, which is the rate that got me to 44k in four years?

thanks for this.

 

[dhanson865]

my bad.
very sorry about that.

I entered the totals and am now trying to understand what I am seeing.
How do I translate what I see to understand changes to range?

But first two pressing questions:
-In terms of "days in the sun"--what do I enter if my parking spot is in the sun part of each day, then the shadow moves over the car around midday? 3.5 or 4?

and

-How do I adjust the mileage vector as my commute (and so yearly mileage) is now about 3.5k a year sted of 11k a year, which is the rate that got me to 44k in four years?

thanks for this.

I wold go for 4 or 5 days in the sun if you mean that it gets partial days over 5 days of parking the effect might be closer to 5 than 4. Once the pavement is heated up it will continue to heat the battery pack from below even after the shadow covers the car.

I'm not sure on the mileage, I'm not on a PC where I can check the spreadsheet.