Capacity Loss on 2011-2012 LEAFs

[edatoakrun]

So with the software update back in April (?), we now have no idea what these bars actually reflect. Interesting...

Actually, the service manual was revised with these changes in April 2011.

Back to my original question:

I've asked several times, of those that have access to this source, that they please post this entire table (?) and any associated text.

IMO, if you choose to rely on Nissan for this information, you should at least try to discern exactly what Nissan is stating. The terms "Capacity" and "15% loss", for example, have multiple possible interpretations.

Most importantly, perhaps, is whether Nissan is saying that these percentage losses are of total battery capacity, or rather of that percentage (possibly variable) of the capacity that the BMS allows us to use between a "100% charge" and the low state of charge warnings, and/or shut down.

http://www.mynissanleaf.com/viewtopic.p ... start=2840" onclick="window.open(this.href);return false;

The Wiki States:

The twelve smaller segments at far right of the battery gauge represents the battery's current maximum capacity. As the battery's capacity degrades, these bars disappear one by one. This table shows the approximate battery capacity represented by each bar [6]:
Segments Retained capacity (%) — Note
12 85 or more T12 —
11 85 T11 Value at which segment 12 turns OFF
10 78.75 T10 Value at which segment 11 turns OFF
9 72.5 T9 Value at which segment 10 turns OFF
8 66.25 T8 Value at which segment 9 turns OFF
7 60 T7 Value at which segment 8 turns OFF
6 53.75 T6 Value at which segment 7 turns OFF
5 47.5 T5 Value at which segment 6 turns OFF
4 41.25 T4 Value at which segment 5 turns OFF
3 35 T3 Value at which segment 4 turns OFF
2 28.75 T2 Value at which segment 3 turns OFF
1 22.5 T1 Value at which segment 2 turns OFF
0 16.25 T0 Value at which segment 1 turns OFF

http://mynissanleaf.com/wiki/index.php? ... acity_Loss" onclick="window.open(this.href);return false;

Is the explanation above the table, and the table itself, directly copied from the pre-April 2011 manual, or did someone else summarize this information?

Was that all the manual said on the subject?

What was the context of the table? Was it presented as a way too accurately diagnose capacity problems, to determine "current maximum capacity", and is that term defined anywhere else in the manual?

Do we have any way to know whether revisions were made to LEAFs, prior to any US deliveries, which make the "approximate battery capacity represented by each bar" in the table, inaccurate?

[Stoaty]

Do we have any way to know whether revisions were made to LEAFs, prior to any US deliveries, which make the "approximate battery capacity represented by each bar" in the table, inaccurate?

No, but I think it is a fair bet that if a change had been made that would put the capacity loss in a more favorable light Nissan would have been all over it publicly.

[ztanos]

My Temp bars are always on six bars. In fact, I have never seen anything else in summer or winter in Florida. No capacity loss yet. Could happen any time.

I used to live in Florida. It doesn't have a winter.

[DarkStar]

So with the software update back in April (?), we now have no idea what these bars actually reflect. Interesting...

Actually, the service manual was revised with these changes in April 2011.

I'm talking about the changes this year.

[edatoakrun]

Stoaty-

I asked earlier:

Where are the "no correlation" results graphed, for the same group of bar loss reports??

I don't understand why you have come to that conclusion, since one axis itself is months since delivery.

I wanted to see what might account for the anomalous 24,000 mile one bar loss report, and only then realized it must be the 10 month/20,000 mile report on the Wiki, right?

Right. To be honest, I don't know which is the correct comparison:

One compares the total miles driven to the time it takes to lose a bar - no correlation
The other compares the rate at which miles are accumulated to the time it takes to lose a bar - moderate correlation

The more I think about it, the more confused I have become. I welcome input from others more knowlegeable than I.

Where are the "no correlation" results graphed, for the same group of bar loss reports?

http://www.mynissanleaf.com/viewtopic.p ... start=2780" onclick="window.open(this.href);return false;

[Stoaty]

Where are the "no correlation" results graphed, for the same group of bar loss reports??

I may not have posted them for the exact same data set. Here is the graph for one bar losers in Phoenix. Correlation coefficient is .0003. I think we can safely say there is no correlation.

[edatoakrun]

Where are the "no correlation" results graphed, for the same group of bar loss reports??

I may not have posted them for the exact same data set. Here is the graph for one bar losers in Phoenix. Correlation coefficient is .0003. I think we can safely say there is no correlation.

Having no expertise in statistical analysis, I am quite willing to be corrected.

But I'd say that you could find a significant correlation in the ~50% of the reports following the trend line, and, as you say, much less correlation in the 100% of the reports graphed.

It would be very interesting if it were possible to isolate the most significant factors in common, for the ~half the LEAFs that are outliers from the (more highly correlated, 50% of reports) trend.

My best guess for the largest single "off the chart" factor, would be ambient temperature, where the LEAFs are parked at night. This probably varies significantly more, than ambient temperature during the day.

[DaveinOlyWA]

Where are the "no correlation" results graphed, for the same group of bar loss reports??

I may not have posted them for the exact same data set. Here is the graph for one bar losers in Phoenix. Correlation coefficient is .0003. I think we can safely say there is no correlation.

Having no expertise in statistical analysis, I am quite willing to be corrected.

But I'd say that you could find a significant correlation in the ~50% of the reports following the trend line, and, as you say, much less correlation in the 100% of the reports graphed.

It would be very interesting if it were possible to isolate the most significant factors in common, for the ~half the LEAFs that are outliers from the (more highly correlated, 50% of reports) trend.

My best guess for the largest single "off the chart" factor, would be ambient temperature, where the LEAFs are parked at night. This probably varies significantly more, than ambient temperature during the day.

i am seeing evidence that very high temps can take more than 36 hours to equalize

[Stoaty]

Having no expertise in statistical analysis, I am quite willing to be corrected.

But I'd say that you could find a significant correlation in the ~50% of the reports following the trend line, and, as you say, much less correlation in the 100% of the reports graphed.

It would be very interesting if it were possible to isolate the most significant factors in common, for the ~half the LEAFs that are outliers from the (more highly correlated, 50% of reports) trend.

You can't pick and choose data to get a correlation. Either there is a correlation (weak, moderate, strong) or there isn't. Otherwise, you could take any data set, decide which half of the points followed the trend you wanted to see and throw the rest out. As I showed in a previous analysis, there IS a moderate correlation between monthly mileage and rate of capacity loss (edit: for those in Phoenix who have lost a capacity bar).

[edatoakrun]

Having no expertise in statistical analysis, I am quite willing to be corrected.

But I'd say that you could find a significant correlation in the ~50% of the reports following the trend line, and, as you say, much less correlation in the 100% of the reports graphed.

It would be very interesting if it were possible to isolate the most significant factors in common, for the ~half the LEAFs that are outliers from the (more highly correlated, 50% of reports) trend.

You can't pick and choose data to get a correlation. Either there is a correlation (weak, moderate, strong) or there isn't. Otherwise, you could take any data set, decide which half of the points followed the trend you wanted to see and throw the rest out. As I showed in a previous analysis, there IS a moderate correlation between monthly mileage and rate of capacity loss.

"Either there is a correlation (weak, moderate, strong) or there isn't."

And clearly, there is a correlation of capacity bar loss with both time and miles driven, whatever adjective you use to describe it.

If bar loss was not correlated to these factors, and an entirely random event, then the entire field of your graph would have more even * distribution.

This would be far more more clearly illustrated, by a graph that had both the X and Y axes originating at zero.

Both of these factors might be expected show far greater correlations in cooler climates. Even more so, if they are restated as time from delivery, and number of charge cycles. But in Phoenix, both of these individual factors are themselves probably reflecting (in varying amounts) a much "strong"(er) correlation, to exposure to high battery temperatures.

I am saying, it could useful to look at the outliers from this "weak" correlation, to isolate the primary causes, of loss of capacity bars in Phoenix.

Since daytime ambient temperatures may have been largely eliminated as a variable factor, by limiting the sample to the Phoenix area, the next factor to look into, IMO, would be ambient temperature while parked, or as you have suggested, charging patterns.

http://www.mynissanleaf.com/viewtopic.php?f=27&t=9744" onclick="window.open(this.href);return false;

*edit