Stoaty's Battery Degradation spreadsheet now for prospects!

Stoaty has worked hard to put together a LEAF battery life estimation spreadsheet that many existing owners/lessees currently use to predict the lives of our batteries. I have recently made a couple of changes which should make this tool more useful for prospective and new LEAF owners to help answer the question "How long should I expect the LEAF battery to serve my needs?" Specifically, the spreadsheet is now online, so there is no need to download any files or install any software to get a quick answer. Also, I have added a new mode of entry for those who do not own a LEAF. Using this mode, you only have to enter the following four things to get battery life estimations:

City: Choose a nearby city from an existing list in the spreadsheet.
Miles/kWh: Estimate your LEAF driving efficiency. If you do not know, 4.0 is a good starting estimate.
Days/week in the Sun: How many days per week will the LEAF be parked in the sun, on average?
Estimated Annual Mileage: How many miles do you expect to drive the LEAF each year?

That's it! Once you have entered that information on the 'Input' tab, you can move over to the 'Prediction' tab and get an estimate for how long you have before your battery capacity crosses below the following percentages of original capacity: 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55% and 50%. Based on how far your commute is and what the temperature is you should be able to choose a percentage to use for your life estimate.

For instance, let's say you live near Denver, CO, and you have a 50-mile round-trip commute. You can use Tony Williams' excellent range estimation chart to predict how far you can travel on a breezy 20F day with a new LEAF at 55 MPH. Let's say about 75 miles. If you are like many here, you don't like to ever get down to fully empty, so let's provide another 10% margin, so maybe 68 miles. 50 miles/68 miles means you need to about 73.5% of your original battery capacity to comfortably make your commute on a fairly cold breezy winter day. So, you can put Denver, CO, 4.0 mi/kWh, 5 days/week and 10000 miles/year into the estimator and read the row for 75% and see that you should be able to make your commute for about the next 6.1 years.

Please note that Stoaty has calibrated this spreadsheet using data from the 2011/2012 LEAFs, so the estimates may not be completely accurate for 2013 or newer models due to possible changes in the battery chemistry. Personally, I suspect it is close for the 2013s, but sometime in 2014 Nissan is promising to deliver a more robust chemistry. If they do that, then this spreadsheet will likely not make useful predictions for such a battery.

Please give it a try for your situation: Stoaty's Online Battery Capacity Estimation Spreadsheet

tried this last night and it works great! my numbers are less than 1% off the predicted values. Very good job BOTH of you

I must have tried the "old" version last week (for the first time), and am VERY impressed with the effort/results. Seemed like this was as good a place as any to say "thanks for the good work": it definitely helps with long-term planning (I should eventually qualify for a new battery under warranty here in Dallas).

Thanks! Now that Stoaty's spreadsheet is updated for accuracy and online, I think it will get a lot more use!

One usage note for the online version: Please do not park your cursor over the "Do you currently own a LEAF?" or the "City" entry cells. Please move them off to a blank cell when you have finished your entry. The reason is that Google Drive spreadsheets puts a little indicator up for others when they try to get to the cell. As a result, if one user is parked in the "Do you currently own a LEAF?" or two users are parked in the "City" entry blocks, the spreadsheet becomes virtually unusable. I'm not sure how to change this other than to simply ask that you don't do that! TIA!

I just tried it, and am studying the results...Is there enough data to report when the loss of the first few capacity bars will occur in addition to the times already reported when 90, 85, 80, 75%, etc capacity will be reached?

Randy said:

I just tried it, and am studying the results...Is there enough data to report when the loss of the first few capacity bars will occur in addition to the times already reported when 90, 85, 80, 75%, etc capacity will be reached?

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My opinion is "Yes" for hot climates and "Likely No" for cooler climates and "Maybe" for in-between climates like where you live in San Diego. I expect that there will need to be further adjustments to the equations/calibration constants as we learn more about degradation in cooler climates.

I'm sure Stoaty may have a different opinion, as we have some level of disagreement over the exact equations to use. Still, Stoaty's equations consistently get within 20% of the target and often much, much closer.

I want a warranty spread sheet. Just plug in the months and miles at bar loss to predict if the 4th bar will be gone before 60/60.

smkettner said:

I want a warranty spread sheet. Just plug in the months and miles at bar loss to pridict if the 4th bar will be gone before 60/60.

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This spreadsheet requires more input than that, but it does predict whether or not you will make the warranty cutoffs. Have a look...

smkettner said:

I want a warranty spread sheet. Just plug in the months and miles at bar loss to pridict if the 4th bar will be gone before 60/60.

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it already does that or at least predicts the 70% SOC date and mileage. FYI; if I were buying, I missed it by about 57,000 miles (or at least I will)

Thanks for the great work in making this easily available on line.
Only problem, is that multiple people can be trying to use it at the same time and the results keep changing.
To use it correctly, I guess you need to park the cursor over one of the entry fields to lock everyone else out?
But when you switch to the Prediction tab, is the Input tab cursor position on an input cell still locking others out?
Need to provide a bit more clarity / instruction to users on how to do this properly.
But great work.

smkettner said:

I want a warranty spread sheet. Just plug in the months and miles at bar loss to pridict if the 4th bar will be gone before 60/60.

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In the original spreadsheet from the Wiki, there was a column for just that.
See "Calibration" tab and column AA - "Qualify for Warranty?"
http://www.mynissanleaf.com/wiki/index.php?title=Battery_Capacity_Loss#Battery_Aging_Model" onclick="window.open(this.href);return false;

stoaty,
thanks for this.
with no AH meter, do i estimate living in a climate similar to santa monica, i.e, that it is 60?
also, do i use carwings for average m/kwh?
or use my estimate off usage on the actual dashboard (not the center console)?
moi

TimLee said:

Thanks for the great work in making this easily available on line.

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You're welcome! Stoaty works in OpenOffice, which is freely available, but I was loathe to install yet another spreadsheet since I already use Excel, Numbers and Google Drive Spreadsheets.

TimLee said:

Only problem, is that multiple people can be trying to use it at the same time and the results keep changing.

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Yes, that is a real issue. But it was worse this morning since there was this thread.

TimLee said:

To use it correctly, I guess you need to park the cursor over one of the entry fields to lock everyone else out?

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No, that doesn't actually work. Even with the pull-downs, you can still manage to use it, although it is quite difficult to do.

TimLee said:

But when you switch to the Prediction tab, is the Input tab cursor position on an input cell still locking others out?

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Nope. But please note that I have duplicated all of the entries from the Input tab over on the 'Prediction' tab. So please keep an eye on those while looking at the prediction to ensure that you did not enter anything incorrectly AND that no one else is on the Input tab making changes. Normally, you will be the only user trying to access the spreadsheet.

TimLee said:

Need to provide a bit more clarity / instruction to users on how to do this properly.

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My tip is to watch for other activity on the Input tab before you start making changes. If you see things moving around, it might be best to wait until the inputs stop changing and then give the other user a few minutes to view their results.

TimLee said:

But great work.

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Thanks! I've used Stoaty's spreadsheet for quite a while, but it was only after a bunch of us got our capacity meters that we could see how accurate it really is!

That said, we are open to suggestions for improvement going forward!

First, thank you, this is awesome.

Second, is 80% charge vs. 100% charge not a big enough deal to include in this? Or just haven't gotten to it/too much of a pain?

goaliepride said:

Second, is 80% charge vs. 100% charge not a big enough deal to include in this? Or just haven't gotten to it/too much of a pain?

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While we disagree on some other things, I believe Stoaty and I agree that 80% versus 100% makes little difference in battery life. In fact, both of us try to keep our LEAFs around 30% SOC since we *think* that helps (but we are not sure).

RegGuheert said:

TimLee said:

But great work.

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Thanks! I've used Stoaty's spreadsheet for quite a while, but it was only after a bunch of us got our capacity meters that we could see how accurate it really is!

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Stoaty's model is amazingly accurate.
I had downloaded and run it about a year back, and was impressed then.
But his recent work to improve it is really impressive.
I like the on line capability as it was quick and easy to do.
But I'll still probably download the spreadsheet, so I can input the specific environmental parameters for Chattanooga.
Nashville is close, but a bit cooler than Chattanooga. And Atlanta is a bit hotter.
But I think I'm a bit ahead of the model, having lost a capacity bar at 16,000. Too much fast driving at 3.3 m/Kwh and too many DCQC possibly, but a garage with no ceiling insulation to keep the heat out of it may also be a factor.
Time to enter the modern world, get the Note 3, buy the ELM, buy the extension cable, buy Leaf Spy Pro and help support Turbo3's impressive development efforts, and start tracking the battery capacity decline real time.
But for now I plan to avoid the P3227 software update, so unfortunately the data won't be going into improvement of Stoaty's model. I don't like the change in regeneration that P3227 does that most are reporting. But my guess is that the dealer will do it whether I want it or not at my three year battery test on May 18, 2014.

I used the "prospect" function to enter ~ generic data from the four LEAFs whose capacity loss is currently being tested in Phoenix by the DOE:

DC Fast Charge Effects on Battery Life and Performance Study – 30,000 Mile Update
Four model year 2012 Nissan Leaf battery electric vehicles were instrumented with data loggers and are being operated over a fixed on-road test cycle. Each vehicle is charged twice daily, with two vehicles charged at AC Level 2 (L2), and two DC fast charged (DCFC) with a 50kW charger. The traction battery packs are removed and tested when the vehicles were new, and at 10,000 mile intervals. Battery tests include constant current discharge capacity, electric vehicle power characterization, and low peak power tests1. The testing will continue to at least 50,000 miles at which point the battery testing results will determine if testing continues in additional 10,000 mile increments. This fact sheet summarizes the measured changes in capacity at 10, 20, and 30 thousand miles relative to baseline test results...

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(30 k mile update)

http://avt.inel.gov/pdf/energystorage/DCFC_Study_FactSheet_30k.pdf" onclick="window.open(this.href);return false;

(for)


DC Fast Charge Impacts on Battery Life and Vehicle Performance

http://www4.eere.energy.gov/vehiclesandfuels/resources/merit-review/sites/default/files/vss113_francfort_2013_o.pdf" onclick="window.open(this.href);return false;

Correct me if I'm wrong, but it appears the model overstates actual capacity loss as reported by this study by a very large margin (for example, predicting 25% capacity loss at 32,000 miles) for both the L2 cars (actual capacity loss ~14%) and getting only a little closer to the results for the DC-charged LEAFs (actual capacity loss ~17%) after 30k miles.



You can plug in any individual and assumed data from any of the four individual LEAFs to see what you get, compared to that I used, and see what the model predicts for you.

IMO, this shows that developing a model which only predicts loss of dash bars, gids, and App-reported capacity losses may be of very limited value, since all evidence indicates those reports from the LEAF's LBC/BMS have little integrity.

Results dated 8/7/13, showing both 20k and 30k mile results.

http://avt.inel.gov/pdf/energystorage/DCFC_Study_FactSheet_30k.pdf" onclick="window.open(this.href);return false;

...The expected accelerated loss of capacity in summer, as well as additional loss of capacity from fast charging, are both showing up IMO, with ~14% capacity loss on L2, and ~17% loss on DC.

If this loss of capacity is different from what you think you are seeing in your hot climate LEAFs, remember this appears to be actual loss of total capacity from discharge tests, not the available (?) battery capacity as reported by your LEAF's LBC, as displayed in dash capacity bars or app/gid meter readouts.

Click to expand...

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http://www.mynissanleaf.com/viewtopic.php?f=27&t=14271" onclick="window.open(this.href);return false;


Of course, when we see the 40,000 mile data from this test, we will have a even clearer view of real capacity loss over a ~full climate year in very severe use (very hot and very high miles driven per day) using both L2 and DC exclusively.

Until then, I wonder if any of you Arizona LEAFer's could get a gid reading, or at least get a look at the dash battery capacity bar display for any of these test LEAFs?

edatoakrun said:

IMO, this shows that developing a model which only predicts loss of dash bars, gids, and App-reported capacity losses may be of very limited value, since all evidence indicates those reports from the LEAF's LBC/BMS have little integrity.

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I'm sure I'm not alone in hoping that you are correct on this point. Like you, I don't feel that I have lost as much range as the meter indicates. OTOH, I did not get the car when it was new.

RegGuheert said:

edatoakrun said:

IMO, this shows that developing a model which only predicts loss of dash bars, gids, and App-reported capacity losses may be of very limited value, since all evidence indicates those reports from the LEAF's LBC/BMS have little integrity.

Click to expand...

I'm sure I'm not alone in hoping that you are correct on this point. Like you, I don't feel that I have lost as much range as the meter indicates. OTOH, I did not get the car when it was new.

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Well, as I wrote, I think the following just might prove an effective antidote to some cases of capacity-loss-anxiety:

..I wonder if any of you Arizona LEAFer's could get a gid reading, or at least get a look at the dash battery capacity bar display for any of these test LEAFs?

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What are the approximate Amp/Hrs at one bar lost, two bar lost, and three bar lost?
And Gids at these levels if needed to plug in.

Not everyone has these fancy tools.