edatoakrun
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Re: Use CW report from range test to determine battery capac

Fri Aug 31, 2012 1:54 pm

Ever since TickTock fist suggested the topic of gid variability, the implications of his observations have been setting in.
TickTock

1 gid *mostly* equals 80Wh
http://www.mynissanleaf.com/viewtopic.php?f=44&t=9689" onclick="window.open(this.href);return false;

If “gids” do reflect a variable amount of Wh, and they are the values used by the LEAF to calculate kWh use, then the capacity bar displays, dash and nav screen displays of m/kWh, as well as the Carwings calculations based on these same “gid” values, might be expected to be incorrect as well.

I now believe that this quite possibly could be be the case.

I have been noticing an unexplained increase in my dash, nav Screen, and Carwings m/kWh results for a few months now, not only on this test trip, but on other trips, and my long term m/kWh averages.

Before I questioned the accuracies both of the screens and of Carwings, I thought the likely explanations for increased efficiency results, were increased efficiency, in either the driver or vehicle.

I am skeptical of any significant increase in my own driving efficiency, other than that resulting from driving more slowly.

I considered the possibility of increasing vehicle efficiency, and I would not be surprised if drivetrain friction is reduced a bit due to “break-in” of the drivetrain.

But if either of these efficiency factors were improving, I would expect them both to be relatively minor, and self limiting.

This does not seem to be what I am seeing.

I think that my range tests may indicate that whatever method my LEAF uses to calculate kWh, is variable, and has been significantly understating the recent amounts of kWh use, and has probably increasingly inflated all my m/kWh reports, from the dash, nav screen, and CW.

And of course, this could reflect with Tick Tocks observations of variable “gid” Wh values. Gids with higher Wh content could lower the calculated kWh numbers, and raise all the m/kWh results.

Maybe this is what I am seeing, from yesterdays range test. I tried to replicate as accurately as possible, my earliest range test,of almost a year, and almost 10,000 miles ago, to test this hypothesis.

I chose a day with very close to the original temperature condition, and drove the exact same route over the first 87 miles of the trip, using the same mode (eco) and used my original trip logs to closely replicate the same elapsed times for each of the three (same distance) legs of the trip.

The results from 8/30/12 were:

97.3 miles to VLB, 98.9 miles in total, by the odometer.


CW: 96.5 (~2.5% under-report) total miles, at 5.7 m/kWh, 16.8 kWh used from 100% to about the same capacity level, slightly past VLBW.

Compare this test with my first test on 9/7/11:

91.5 miles to VLB, 93.4 in total, by the odometer


CW: 91.1 (~2.5% under-report) total miles, at 4.9 m/kWh, 18.7 kWh used from 100% to about the same capacity level, slightly past VLBW.

I do not believe that the slight increase in range over the last year reflects any increase in battery capacity. On the contrary, I expect that my total capacity ( though maybe not the amount of kWh that the BMS is allowing me to access) has declined by an undetermined amount, but it cannot be detected due to the “noise” of uncontrolled variables in a range test.

But I think the decrease of over 10% of reported kWh use, is simply too great to be consistent.

And for those who doubt CW accuracy or consistency, in calculating that total, I’d point out each of the replicated legs of this trip, and of half a dozen other trips I’ve monitored this month, match the m/kWh dash reports precisely.

Both are probably incorrect, BTW, but by about the same 2.5% odometer error rate. So if you can’t or won’t use CW, I think the nav screen m/kWh is probably using the correct “miles driven”, and will probably be reasonably accurate as long as you have factory tires with most of their tread.

Neither the dash or Nav screen results will tell you much though, IMO, unless you can pin down what they are using for a “kWh” value. and if you are using a gid count to calculate kWh, I’d suggest again, that you check to see whether TickTock’s findings of gid variability are correct.

I could write pages of details on these tests, and will answer any specific questions about my methodology.

However, I think that the real key to understanding what is going on, is to have multiple reports of range tests, comparing initial and “reduced capacity” batteries, rather than extrapolations based on m/kWh reports, gid counts, or GOM readings.

An alternate, and perhaps an even better way of calculating actual kWh use is by taking “from the wall” measurements. Though you will always have a variable in charge efficiency, you should be able to be able to get a pretty good estimate by either a meter or charge time.

I don’t have a meter, but I do do have my recharge time from 9/7/11 logged, at ~ 4 hours and 25 minutes to “80%”.

Unfortunately, I did not get a charge completed Email this AM (poor cell reception?) so I cant compare the two times. Next time I get to VLB, I will be sure to finish charging while I am awake, and watch for the results.
Last edited by edatoakrun on Mon Sep 10, 2012 2:13 pm, edited 2 times in total.
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KJD
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Re: Use CW report from range test to determine battery capac

Fri Aug 31, 2012 2:48 pm

CW: 96.5 (~2.5% under-report) total miles, at 5.7 m/kWh, 16.8 kWh used from 100% to about the same capacity level, slightly past VLBW.
5.7 m/kwh is a pretty good number. What was your average speed during this test ?
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spooka
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Re: Use CW report from range test to determine battery capac

Fri Aug 31, 2012 3:22 pm

Looking at the data in this thread and as a newbie with no instruments available to collect data other than the info I get from the instrument panel on my Leaf, I am wondering if this would be a way to at least guesstimate my battery degredation.

On September 8, 2011 I made a 40 mile trip and repeated the same trip today. Both days were the same temp and I checked tire pressure before driving. Drove Eco mode the whole way. The only difference is that I have 10 bars on the capacity scale now. The charge state bars remaining in both cases after my 40 mile drive had just dropped to the next level and were esentially full bars. Charged to 100% both times.

Leaf dash on 9/8/11
5.8 miles/kwh 41.2 miles driven 6 bars remain 48 miles left on the GOM

Leaf dash on 8/31/12
6.6 miles/kwh 41.3 miles driven 5 bars remain 39 miles left on the GOM



This is my guess on how I can obtain a CRUDE estimate of capacity loss based on this info. Please provide any thoughts on this. Just to restate, I am not an engineer or even trying to be one. I am trying come up with a crude formula that us non-techies can use.


I want to use the data provided by the Leaf console to determine the total amount of kwh available to me in the battery pack on each day. I will use this number to determine percentage lost in the battery pack over the period of the last year.


2011 trip

41.2 miles driven divided by 6 bars depleted = 6.86 miles/bar
if I could continue that average for all 12 bars, I could roughly obtain a total of (6.86 miles/bar * 12 bars) 82.4 miles on this charge
82.4 miles divided by the Leaf's reported 5.8 miles/kwh average = 14.28kwh available to use on this charge


2012 trip

41.3 miles driven divided by 7 bars depleted = 5.9 miles/bar
if I could continue that average for all 12 bars, I could roughly obtain a total (5.9 miles/bar * 12 bars) 70.8 miles on this charge
70.8 miles divided by The Leaf's reported 6.6 miles/kwh average = 10.73kwh available to use on this charge

Now to compare the total available charge (capacity) from 2011 and 2012.

10.73kwh divided by 14.28kwh x 100 = 75%


Since I have lost 2 capacity bars up to this point, 75% capacity remaining would fall in line with the manual (with expectation that I will be losing my 3rd bar relatively soon). :evil:

Comments/thoughts please.
Last edited by spooka on Fri Aug 31, 2012 3:44 pm, edited 3 times in total.

edatoakrun
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Re: Use CW report from range test to determine battery capac

Fri Aug 31, 2012 3:29 pm

KJD wrote:
CW: 96.5 (~2.5% under-report) total miles, at 5.7 m/kWh, 16.8 kWh used from 100% to about the same capacity level, slightly past VLBW.
5.7 m/kwh is a pretty good number. What was your average speed during this test ?
Yes, it is a "pretty good number" Too good, IMO.

Please read my comment again. My main point is that the m/kWh from my dash, Nav screen, and CW, are (quite possibly) currently significantly inflated.

Both trips took about 145 minutes to the 87 mile point, excluding the time spent at the same two locations I parked, on both trips.

However, I don't think very useful to calculate an "average" speed on this route, since speeds vary from under 10 to over 50 mph, and there are several stop lights, and always other road conditions, requiring multiple additional full stops, of varying lengths of time.

On both trips, I "Averaged" about 45 mph for the ~45 miles of highway, and under 30 mph, for the ~42 miles of lower-speed roads, including ~8 miles of unpaved roads. After the ~87 mile round trip, it's all low speed, to get to VLBW point.

Take a look at the map and profiles on the first page of the thread, for more details.
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RegGuheert
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Re: Use CW report from range test to determine battery capac

Fri Aug 31, 2012 3:34 pm

spooka wrote:Comments/thoughts please.
Thanks for providing this data and analysis!

The problem with extrapolating from bars is that the charge bars appear to be nonlinear in weight AND there is a fixed offset of a certain amount of kWh below the bottom bar. As a reasult of the offset and nonlinearity you cannot perform an accurate extrapolation of the type you are doing. Also, the bars have about 2 kWh of ambiguity (thickness) to them. Generally, the best data we can get comes between full and one of LBW, VLBW or turtle.

Still, it is interesting to consider your data. Every bit we can collect helps us learn more. Thanks!
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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RegGuheert
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Re: Use CW report from range test to determine battery capac

Fri Aug 31, 2012 4:14 pm

Here is some data contrary to that provided by Ed. When I am looking for 100% to LBW or VLBW data I generally head over to Dave's 100-mile thread.

N1ghtrider from the Miami area is the king of 100-mile runs, having done it about 14 times. drees has been kind enough to compile the data from his many runs. I have copied that table below:
drees wrote:

Code: Select all

12/31/11 111.0 mi 5.9 mi/kWh LBW 102 mi  no VLBW                 18.8 kWh used
 1/05/12 103.1 mi 5.4 mi/kWh LBW 93.3 mi  VLBW?                   19.1 kWh used
 1/13/12 125.4 mi 6.1 mi/kWh LBW 103 mi   VLBW 114 mi             20.5 kWh used
 1/22/12 130.1 mi 6.4 mi/kWh LBW 105.8 mi VLBW 121 mi             20.4 kWh used
 2/17/12 126.1 mi 6.1 mi/kWh LBW 98.1 mi  VLBW 114.3 mi TTL 126.0 20.7 kWh used
 2/26/12 102.0 mi 5.8 mi/kWh LBW 92.3 mi  no VLBW                 17.6 kWh used
 3/03/12 105.1 mi 5.7 mi/kWh LBW ? GOM 6  no VLBW                 18.5 kWh used
 3/10/12 101.3 mi 5.8 mi/kWH LBW ? GOM 8  no VLBW                 17.5 kWh used
 3/24/12 106.3 mi 5.7 mi/kWH LBW 93.2     no VLBW                 18.7 kWh used
 3/29/12 106.2 mi 5.8 mi/kWh LBW 91.3     VLBW 105.7              18.3 kWh used
 4/06/12 111.3 mi 5.8 mi/kWh LBW 91.8     VLBW 108.9              19.2 kWh used
 4/11/12 107.3 mi 6.0 mi/kWh LBW 96.0     no VLBW                 17.9 kWh used
 7/21/12 100.0 mi 5.8 mi/kWh LBW 84.4     no VLBW                 17.2 kWh used
As you can see, N1ghtrider's efficiency has not gone up (or down) much over time, but the number of miles he drives from full to LBW has gone down.

This seems to be a contrarian case to Ed's recent run. Sigh.

Thoughts?
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

edatoakrun
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Re: Use CW report from range test to determine battery capac

Fri Aug 31, 2012 6:41 pm

RegGuheert wrote:Here is some data contrary to that provided by Ed. When I am looking for 100% to LBW or VLBW data I generally head over to Dave's 100-mile thread.

N1ghtrider from the Miami area is the king of 100-mile runs, having done it about 14 times. drees has been kind enough to compile the data from his many runs. I have copied that table below:
drees wrote:

Code: Select all

12/31/11 111.0 mi 5.9 mi/kWh LBW 102 mi  no VLBW                 18.8 kWh used
 1/05/12 103.1 mi 5.4 mi/kWh LBW 93.3 mi  VLBW?                   19.1 kWh used
 1/13/12 125.4 mi 6.1 mi/kWh LBW 103 mi   VLBW 114 mi             20.5 kWh used
 1/22/12 130.1 mi 6.4 mi/kWh LBW 105.8 mi VLBW 121 mi             20.4 kWh used
 2/17/12 126.1 mi 6.1 mi/kWh LBW 98.1 mi  VLBW 114.3 mi TTL 126.0 20.7 kWh used
 2/26/12 102.0 mi 5.8 mi/kWh LBW 92.3 mi  no VLBW                 17.6 kWh used
 3/03/12 105.1 mi 5.7 mi/kWh LBW ? GOM 6  no VLBW                 18.5 kWh used
 3/10/12 101.3 mi 5.8 mi/kWH LBW ? GOM 8  no VLBW                 17.5 kWh used
 3/24/12 106.3 mi 5.7 mi/kWH LBW 93.2     no VLBW                 18.7 kWh used
 3/29/12 106.2 mi 5.8 mi/kWh LBW 91.3     VLBW 105.7              18.3 kWh used
 4/06/12 111.3 mi 5.8 mi/kWh LBW 91.8     VLBW 108.9              19.2 kWh used
 4/11/12 107.3 mi 6.0 mi/kWh LBW 96.0     no VLBW                 17.9 kWh used
 7/21/12 100.0 mi 5.8 mi/kWh LBW 84.4     no VLBW                 17.2 kWh used
As you can see, N1ghtrider's efficiency has not gone up (or down) much over time, but the number of miles he drives from full to LBW has gone down.

This seems to be a contrarian case to Ed's recent run. Sigh.

Thoughts?
Well, I think that you would expect to see results like this if his actual m/kwh were declining, due, (for example) to a seasonal increase in AC use which does, in my experience, does cause quite significant reductions in m/kwh during slow-speed trips.

Again, without eliminating variables like speed and climate control use, you really can't conclude anything from the range numbers, IMO.

Note our exchange from "I Beat EPA's 2.9 Miles/KWh : Report Your Monthly Mileage" thread:
N1ghtrider wrote:
Dec/2011 Platinum 574 5.2 miles/kWh
Jan/2012 Platinum 750 5.2 miles/kWh
Feb/2012 Platinum 848 5.2 miles/kWh
Mar/2012 Platinum 769 5.4 miles/kWh
Apr/2012 Platinum 1179 5.3 miles/kWh
May/2012 Gold 2716 4.8 miles/kWh
.

A/C usage and more interstate driving cut my m/kWh to below 5 for the first time.
Edatoakrun

And I got over 5 m/kWh on my CW monthly report for the first time.
My 540 mile drive (on an L2 trip, the slower you drive, the faster you'll get there) to the San Francisco bay area and back, helped to raise the average.

I also had my greatest miles per single charge on 5/31, 105.8 miles (with about a mile each, of ascent and descent!) by my odometer, reported by CW as 103.2 miles at 5.9 m/kWh.

CW continues to under-report miles driven by about 2.5%, so I believe all the m/kWh numbers below should be adjusted upward by the same 2.5%, for greatest accuracy.

Month and Year Grade Rank Energy Economy
*Jun/2011 Gold 695 5.7 miles/kWh
*Jul/2011 Gold 1651 5.3 miles/kWh

Aug/2011 Bronze 3622 4.2 miles/kWh
Sep/2011 Silver 3457 4.5 miles/kWh
Oct/2011 Silver 3640 4.2 miles/kWh
Nov/2011 Gold 2792 4.2 miles/kWh
Dec/2011 Gold 2827 4.0 miles/kWh
Jan/2012 Gold 2547 4.2 miles/kWh
Feb/2012 Gold 2354 4.4 miles/kWh
Mar/2012 Gold 2975 4.3 miles/kWh
Apr/2012 Gold 3018 4.5 miles/kWh
May/2012 Gold 1978 5.1 miles/kWh

*Prior to CW update. Disregard, as correction factor unknown...
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RegGuheert
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Re: Use CW report from range test to determine battery capac

Fri Aug 31, 2012 7:05 pm

edatoakrun wrote:Again, without eliminating variables like speed and climate control use, you really can't conclude anything from the range numbers, IMO.
This certainly is a tough nut to crack!

It seems clear that Nissan may have gone a little too cheap on instrumentation, possibly making an issue with battery life appear even more severe than it already is.

Here is a paper from Analog Devices about various techniques for making current measurements for energy metering. I believe Phil has said that the LEAF uses Hall Effect sensors. Perhaps Nissan needs to look into using the Rogowski Coil technique discussed in this paper.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

Herm
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Re: Use CW report from range test to determine battery capac

Fri Aug 31, 2012 8:43 pm

RegGuheert wrote: It seems clear that Nissan may have gone a little too cheap on instrumentation, possibly making an issue with battery life appear even more severe than it already is.
We have been talking about this for years.. can you trust the Nissan instrumentation?.. you dont know until you measure the energy used directly at the battery cables.. everything else has always been circular reasoning chasing its tail. Everyone in Phoenix is now hoping the the battery capacity meter is faking it somehow and lost capacity will return in winter.

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DaveEV
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Re: Use CW report from range test to determine battery capac

Sat Sep 01, 2012 12:08 am

edatoakrun wrote:An alternate, and perhaps an even better way of calculating actual kWh use is by taking “from the wall” measurements. Though you will always have a variable in charge efficiency, you should be able to be able to get a pretty good estimate by either a meter or charge time.
IMO - an accurate wall-meter (need at least 0.1 kWh resolution) will easily confirm any drift in the dash's mi/kWh gauge.
edatoakrun wrote:I don’t have a meter, but I do do have my recharge time from 9/7/11 logged, at ~ 4 hours and 45 minutes to “80%”.
Unfortunately, unless you can confirm that wall-voltage was the same, this may not help.

Come to think of it - even measuring from the wall will have some inaccuracy depending on when the BMS decides to stop charging. We all know there can be some significant variation when charging to 100% - and it appears that there is some variation when charging to 80% as well.

At a minimum, you'd have to average the data over multiple runs to be sure.

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