Use CW report from range test to determine battery capacity

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edatoakrun

Well-known member
Joined
Nov 11, 2010
Messages
5,222
Location
Shasta County, North California
A few months after I got got my LEAF, with about 3,300 miles on the odometer, I decided to use a range test from a 100% charge to near the VLBW, to try to determine how driving variables effect energy use, and changes in range and/or battery capacity over time. After I realized that Carwings was updated and reporting consistently, I could further correlate range to actual kWh use, and battery capacity. When testing, I log speed, capacity bar disappearance (and appearance) , battery warnings, and (more recently) temperature. I would suggest any LEAF owner only interested in tracking battery capacity, just watch the total kWh use reports, to provide more precise information than provided by the dash displays.

I do not have a gid meter or other SOC indicator (not that there’s anything wrong with that) If you do have or will get one (Leafscan?) you could, of course, also analyze your kWh use and capacity by that, or other methods.

But my suggestion would be that you can simply use Carwings, for data of total kWh use between whichever initial charge % and charge end point you select. Any inaccuracies in the CW reports, IMO, are probably not nearly as significant to accuracy, as other variables, such as the “100%” charge level, the battery warnings levels, and unknown battery temperature effects, to name just a few.

About another 6,500 miles and nine months after my first range test, and after repeated tests in different conditions, I feel certain that my capacity loss is fairly small. Perhaps the largest variable remaining, is battery temperature when charging. Unfortunately, IMO, we have not gathered sufficient data to understand the larger amount of total battery capacity accepted by a warmer battery, and how much, and at what high temperature, the total charge may begin to be limited, temporarily or permanently, by the charge management system.

My earliest range test, on a hot Summer afternoon:

On 9/7/11.... When I reached my driveway, at 87 miles, I still had (less than) one bar, so I drove until I got the "very low battery" warning and simultaneously lost the last bar, at 91.5 miles. I got home with 93.4 miles, and between 5,500 and 6,000 ft. of ascent and descent, at an average speed of about 40 mph (those last 6.4 miles were up and down a hill at low speed). Since the last 1.9 miles after the "very low battery” warning were at about 20 mph and required about 150 ft. net descent with regen, I was probably still very close to the VLBW point capacity, when I parked.

According to CW, on this drive I used 18.7 kWh to drive 91.1 miles at average energy economy of 4.9 m/kWh.

I rechecked 2 other recent drives of 85-105 miles and each time CW has erred, under-reporting distance traveled, as compared with both my odometer and Google Maps, by 2.5%, +/- 0.1%....

Extrapolating from the chart, it appears CW may be saying the 1.7 kWh (8.5% from the chart, of 20.4 total kWh-anyone have a better number?) I had left at or near VLBW implies total available battery capacity of about 20.4 kWh.



http://www.mynissanleaf.com/viewtopic.php?f=31&t=5423&hilit=carwings+update&start=10" onclick="window.open(this.href);return false;


This drive was over the first 44 miles of this trip profile below, returning on the same route, with the added miles by repeating the first few miles.

1336599496-21268.png


On 5/31/12, I repeated the same drive, under similar hot weather conditions, covering the entire profile, with a second short loop added at the end, which totaled 47 miles by the odometer. I repeated ~miles 2-4 a half dozen times at the end till I got the VLBW, and including these miles and about 0.7 mile and about 200 ft. of altitude not on the Map, I drove 104.2 miles, to VLBW, and 105.8 miles in total, by odometer, including, I estimate, between 5,500 to 6,000 ft. of both ascent and descent..

I was not trying to replicate speed or other factors leading to my earlier m/kwh performance on this trip, just trying to find the kWh capacity between 100% charge and the same end point, about the the same short trip home (I now believe that to be about 0.2 kWh, of use, BTW) past the VLBW. I was also shooting for over 100 miles, so that I can now answer “how far..?”, with “106 miles, including a mile of up, over Hatchet MT summit, both ways”.

CW report for the 5 “trips” (# 4 is a just a start/stop cycle) is:

trip total Consum regen distance energy econ

1 8.8kWh 10.8kWh 2.0kWh 42.6miles 4.8miles/kWh
2 0.4kWh 0.7kWh 0.3kWh 3.3miles 8.6miles/kWh
3 0.6kWh 0.8kWh 0.2kWh 3.3miles 5.3miles/kWh
4 0.0kWh 0.0kWh 0.0kWh 0.0miles 0.0miles/kWh
5 7.7kWh 11.3kWh 3.6kWh 54.0miles 7.0miles/kWh


I expected higher m/kWh, as my additional miles were all low speed, and relatively level (see trips #2 and #3 above) as opposed to the ~20 miles both way of 55 mph highway over the high pass, in the middle of this trip. When I got the CW report, which is 17.5 kWh, 5.9 m/kWh, and (uncorrected) 103.2 miles, I was initially surprised by the high m/kWh, and somewhat disappointed by the low kWh capacity, which could indicate about 6% (1.2 kWh) capacity loss over this period. However, I searched my old posts, and found a partial explanation, in this low temperature report, of the same test route.

On (corrected date-9/7/11) the overnight low was in the low 60’s, and the top off was done when the ambient temp had warmed to the mid 80’s , and my best estimate that the battery was probably in the 70’s at this time. The drive was done in temperatures of 80-95 degrees. I believe (but did not record) that the battery temp indicator remained at 6 bars for the entire trip...When I made the (almost) identical drive on 11/8 of 88 miles (85.9 as reported by CW) CW reported 17.6 kWh consumed and 4.9 m/kWh. I believe my total battery capacity when I left home with a 100% charge was probably close to 19.4 kWh.

http://www.mynissanleaf.com/viewtopic.php?f=31&t=6701&start=60" onclick="window.open(this.href);return false;

I’m on PG&E E9A TOU rate now, and on 5/31/1 I charged from 80%-to 100% before 7:00 AM, at ambient temperature about 20-25F lower than I had on 9/7/11. I was still at 5 bars temp when I began the days drive on the afternoon of 5/31 at near 90 F ambient, but got a 6th bar within a few miles.

I had forgotten I had charged just before I drove, at much higher temperature, on the first test, on 9/7/11.

Oops.

My other observations have led me to believe that this cooler ambient charge temperature might be expected to reduce kWh capacity by about (?) 3%, so my total loss could be more like 3%, more or less, with the many other unknown uncertainties. I have several reports of 60-something F ambient charges, leading to 17.-something kWh capacity, but have none at a significantly higher temperature, since last summer.

I probably will try one more test, when the temp get back to the 90’s, and then wait till later in the day, to charge to 100%, and hope to get somewhere closer to the 18.7 kWh I got last year.

6/18 edit-Yesterday, 110.9 miles to VLB, 112.7 in total, by the odometer, with close to 6,000 ft of ascent and descent.


I think (and hope) my battery capacity is still so close to “new” (the initial test was after about 3,300 miles, and several Summer months) that it may be a while longer, before I can find a significant loss in capacity, by this method.

However, if you suspect you have a significant loss of capacity, say the “15%” the 12th bar loss is reported to show, I think a range/kWh test, such as this, would be very useful, as a capacity loss of that order, should show up above the other “noise” of range-affecting factors.

6/22 edit:

Revised title from previous "Range test-determine initial/reduced LEAF battery capacity"


8/1/12 edit:

Here is an updated one-way trip profile, showing the miles I have since added at the end, after it became clear my original course was not long enough.


MonumentRocktohwy89494mileprofile.png


The second vertical line on the profile corresponds to destination C on the map below. This is my primary destination, Burney Falls State park.

MonumentRocktoClarkCreekandhwy89rangetestmap.png
 
6/17 capacity test results:

110.9 miles to VLB, 112.7 in total, by the odometer, with close to 6,000 ft of ascent and descent.

CW: 109.9 (~2.5% under-report) total miles, at 6.3 m/kWh, 17.5 kWh used from 100% to about the same point, slightly past VLBW.

Details to follow.
 
Not to belittle your work, but I prefer data from a guid-o-meter or a stationary test under controlled conditions. IIRC the shop manuals specifies the use of the heater to discharge the battery in a set amount of time.. you cant guarantee that each Leaf will use the same heating power but it should be consistent on your own Leaf from year to year, and you can do it in your own garage.
 
Herm said:
Not to belittle your work, but I prefer data from a guid-o-meter or a stationary test under controlled conditions. IIRC the shop manuals specifies the use of the heater to discharge the battery in a set amount of time.. you cant guarantee that each Leaf will use the same heating power but it should be consistent on your own Leaf from year to year, and you can do it in your own garage.

I've considered using the heater for discharge, but:

A full battery pack test, would be a significant waste of energy, IMO.

My objection to using the heater to take the capacity down to Turtle, after a road test, is simply that I own my battery, and a 100% to VLBL test is all I want to subject my battery to.

Sooner or later, I may need the additional range from VLBW to turtle.

But after over 13 months and 10,000 miles, that hasn't happened yet.

If and when it does, I expect to have CW record that kWh usage from the bottom of the pack.
 
Herm said:
Not to belittle your work, but I prefer data from a guid-o-meter or a stationary test under controlled conditions. IIRC the shop manuals specifies the use of the heater to discharge the battery in a set amount of time.. you cant guarantee that each Leaf will use the same heating power but it should be consistent on your own Leaf from year to year, and you can do it in your own garage.

Ok, but what if you don't have a Gidmeter? Besides, Gidmeter shows stored energy, not range. What if a disc brake is dragging, or a tire is low?

I've read the shop manual, and in my opinion, it uses some pretty crude data for technicians. One is using the GuessOmeter to determine range.

No thanks.
 
TonyWilliams said:
Ok, but what if you don't have a Gidmeter? Besides, Gidmeter shows stored energy, not range. What if a disc brake is dragging, or a tire is low?

Guid-o-meter..

How about if your alignment is off?.. if your range is significantly lower the first thing you will assume is that the battery capacity dropped. So you still will have a nagging need to test the battery. The heater test should give you consistent running times (5 hours) from year to year, assuming the temperature in the garage is fairly constant... it is just more convenient than driving up and down a mountain. I assume the heater will stop automatically at VLBW..

Testing how many kWh it took to recharge the battery will also give you a consistent number that you can use to keep track of battery capacity over the years, but it only applies to your own car due to the variables of charging.. as long as you have an accurate way of measuring the energy. Range is so dependent on other factors that it is almost useless for this purpose.

So in conclusion, if you want to test your battery.. discharge it to a set point (LBW is sufficient), and then measure how much it takes to recharge.. not sure I would trust carwings for this. You only have 1000 cycles of life so dont go crazy doing this too often.
 
TonyWilliams said:
Besides, Gidmeter shows stored energy, not range. What if a disc brake is dragging, or a tire is low?
You're actually making Herm's argument for him. If you want to measure battery capacity then range is irrelevant at best and misleading at worst. Obviously wh/mile can differ depending on circumstances. If his brake was dragging and his tires were low and the wind was howling on the route the first time, then the fact he got more range on a subsequent attempt when his brakes weren't dragging and the tires weren't low and the wind was still doesn't establish that his battery capacity has increased.
 
In my experience, for those that have a Gid meter or BCM, it's really accurate and soooo much easier and quicker. Obviously, if one doesn't have one, the other method would just have to suffice. With my BCM, I've read a 14% loss for two people so far, and shortly thereafter, they both lost a capacity bar.
 
SanDust said:
TonyWilliams said:
Besides, Gidmeter shows stored energy, not range. What if a disc brake is dragging, or a tire is low?
You're actually making Herm's argument for him. If you want to measure battery capacity then range is irrelevant at best and misleading at worst. Obviously wh/mile can differ depending on circumstances. If his brake was dragging and his tires were low and the wind was howling on the route the first time, then the fact he got more range on a subsequent attempt when his brakes weren't dragging and the tires weren't low and the wind was still doesn't establish that his battery capacity has increased.

I see it different. A real range test is the only thing that tells you how far it will go (hence my posted parameters). It has nothing to do directly with battery capacity, given other variables. That is for the user to find and determine.

That's why I suggest driving and ANY OTHER DATA to support that (except known bad sources). So, again, driving plus LEAFscan, Gidmeter, Consult III, et al, to analyze the actual range. That is not exclusive, one over the other.
 
TonyWilliams said:
I see it different. A real range test is the only thing that tells you how far it will go (hence my posted parameters). It has nothing to do directly with battery capacity, given other variables. That is for the user to find and determine.
No doubt you'd get a lot more range out of a Leaf over the same route as I would. No argument there. But the OP was trying to use his range on a given route as proof that his battery hadn't degraded. That's different. His battery might not have lost capacity but getting the same range on two different attempts doesn't prove that. For example if I did the first attempt and you did the second then if range indicates battery capacity we'd have to conclude the battery capacity was going up. Then when I did a third attempt we'd have to conclude it was going down!
 
SanDust said:
TonyWilliams said:
I see it different. A real range test is the only thing that tells you how far it will go (hence my posted parameters). It has nothing to do directly with battery capacity, given other variables. That is for the user to find and determine.
No doubt you'd get a lot more range out of a Leaf over the same route as I would. No argument there. But the OP was trying to use his range on a given route as proof that his battery hadn't degraded. That's different. His battery might not have lost capacity but getting the same range on two different attempts doesn't prove that. For example if I did the first attempt and you did the second then if range indicates battery capacity we'd have to conclude the battery capacity was going up. Then when I did a third attempt we'd have to conclude it was going down!


That, I absolutely agree with. That's why there's specific guidelines in my range protocol to eliminate variables like regeneration, etc.

Thanks for clarifying.
 
What the two of you have clarified, is that you are both unaware of Carwings use, and do not comprehend the plain language of my OP.
SanDust:: ...the OP was trying to use his range on a given route as proof that his battery hadn't degraded....

No, I was not. And please do not misrepresent my posts, in the future, as you have so often done in the past.

I explicitly stated that the CW energy report, not a range test, is the most accurate method. of assessing kWh use between different battery pack SOC indicators.:

...you can simply use Carwings, for data of total kWh use between whichever initial charge % and charge end point you select. Any inaccuracies in the CW reports, IMO, are probably not nearly as significant to accuracy, as other variables, such as the “100%” charge level, the battery warnings levels, and unknown battery temperature effects, to name just a few...

(and on the recent tests) I was not trying to replicate speed or other factors leading to my earlier m/kWh performance on this trip, just trying to find the kWh capacity between 100% charge and the same end point...

And I reported that in both recent tests, CW indicated 17.5 kWh use in both recent test from 100% charge to just past VLBW, as opposed to 18.7 in my first test, last Summer.

So, in the simplest analysis, I could conclude this about a 6% reduction in battery capacity was evidence of “degradation”.

However, I believe that there are other factors which cause both the “100%" charge level, and the level of the LBW, to occur at different levels of total capacity.

And I would not make any assertion, of what part of this reduction was a permanent loss in battery capacity, as opposed to a reduction in access to my total battery capacity, imposed by my LEAF’s battery management system.

TonyWilliams:

...That's why there's specific guidelines in my range protocol to eliminate variables like regeneration, etc...

Tony, I would suggest you consider that all three of my range tests I reported here would be impossible on a single charge under your “guidelines”.

This is largely due to your underestimation of recovery of ascent energy, as posted in your range chart, at 50%-75%.

I would think you would come to the same conclusion if you took a look at your energy use during the large ascent/descent segments of your recent BC/BC drive, and would suggest you do so, and correct your range chart to reflect this reality.

Of Course, if you look at the CW reports for the same stretches of road on your recent trip, you should have a far more accurate database to consider.

IMO, there is some more useful information, beyond battery capacity, to be gleaned from my logs of these trips, and I will post more details, as time allows.

The most important point I’d like to make, is that if any suspect you have a significant loss of capacity, such as the “15%” or more that the 12th bar loss is reported to show, I think a range and Carwings kWh use test, such as this, would be very useful, as a battery capacity reduction of that order, should show up much more clearly, above the other “noise” of other available battery capacity and range-affecting factors.
 
Does anyone have an opinion as to whether the update performed at my one-year service check did anything to decrease effective battery capacity? The advisor gave me a 2012 manual and said the car should charge in less time due to update, suggesting they lowered the capacity, possibly to extend life. Or did they recalibrate the way the bars read out? My estimate is that I got about 10 miles from the first bar after 100% charge just prior to update, and now about 5 miles. I have 22K miles and 13 months of driving on my 2011 SL.

Charles
 
Once gain, the dealer has given bad information. What the update DID do was increase the accuracy of the charging time estimate but the actual time did not change. I saw absolutely no change in range before and after the update, and my bar behavior is as it was before the update. BTW, 10 miles on the first bar, assuming level terrain and other than a considerably low speed, would be exceptional and unusual...

chasjacks said:
Does anyone have an opinion as to whether the update performed at my one-year service check did anything to decrease effective battery capacity? The advisor gave me a 2012 manual and said the car should charge in less time due to update, suggesting they lowered the capacity, possibly to extend life. Or did they recalibrate the way the bars read out? My estimate is that I got about 10 miles from the first bar after 100% charge just prior to update, and now about 5 miles. I have 22K miles and 13 months of driving on my 2011 SL.
 
due to update, suggesting they lowered the capacity, possibly to extend life.

Actually they didn't suggest capacity lowering, it was my presumption. At any rate, I definitely see less distance from first bar now, and maybe it's just coincidence I noticed and that my range decrease on that bar was gradual. I typically drive the first five miles at 25-30 mph avg each way to get to freeway, then up to another 3 miles at low speed until traffic speeds pick up where freeway is less congested. It might have been more like 8 miles on first bar before.
 
edatoakrun said:
What the two of you have clarified, is that you are both unaware of Carwings use, and do not comprehend the plain language of my OP.
...
No, I was not. And please do not misrepresent my posts, in the future, as you have so often done in the past.
...
I explicitly stated that the CW energy report, not a range test, is the most accurate method. of assessing kWh use between different battery pack SOC indicators.:
Sorry if I misinterpreted what you were saying. However, if all you're trying to say is that you start with a 100% charge, run the car until you get a VLB warning, and then use CarWings to see how many kWh you used, why not just say that and skip all the extraneous and extensive range discussion? Just say: I run the car until I get the VLB warning. The next day I check CarWings to find the amount of energy used, which is simply "Energy consumed by the traction motor" + "Energy consumed by the vehicle accessories" - "Energy captured by regenerative braking".

Not valid given how imprecise CarWings is but at least it's clear.
 
There is a lot of merit to the method what OP is suggesting. In essence if Carwaings says I spent 19 kWh from 100% to VLB today and in a month it says I used 18kWh for the same two checkpoints, that means I have lost around 1/19 % = 5.2%.

Seems like a clean way to measure capacity loss, except that you should do that with climate control off (to remove variations between two runs) and also same route.
 
mkjayakumar said:
There is a lot of merit to the method what OP is suggesting. In essence if Carwaings says I spent 19 kWh from 100% to VLB today and in a month it says I used 18kWh for the same two checkpoints, that means I have lost around 1/19 % = 5.2%.

Seems like a clean way to measure capacity loss, except that you should do that with climate control off (to remove variations between two runs) and also same route.
What possible difference would climate control make? All you're doing is relying on CarWings to tell give you the total energy expenditure from 100% charge to VLB warning. Doesn't matter what the energy was used for. As Herm mentioned, if you can trust CarWings to give you accurate numbers, which admittedly is a bit crazy, you could just run the heater and not even move the car.
 
On 7/31 I tried another range/Capacity test on my usual route. I wanted to see if the recent hotter temperatures might have caused a more rapid seasonal decline in capacity, akin to those reported by gid counts, and in more severe climates, bar loss.

Unfortunately, I had a Nav system failure after 55.4 miles, while stopped on my return leg at the second vertical bar on the trip profile on p 1 of this thread.

http://www.mynissanleaf.com/viewtopic.php?f=30&t=9573" onclick="window.open(this.href);return false;

However, as I was tracking each bar loss as I drove, and did receive the LBW (without the voice-over) I did get a fairly accurate Idea of my capacity relative to my most recent previous test on 6/17. I believe any additional capacity loss was negligible.

Miles at loss for the first 8 bars, and was either at or trailing my previous trip slightly, but only (speed and grade adjusted) representing a small fraction of a kWh of use.

I got the LBW twice-the first time that ever happened to me.

The first LBW (to my great aggravation) was just before Hatchet MT Summit, 72.4 miles into the trip.

The LBW went off, 12.5 miles later, as I regened on the downgrade, then came on again in another 6.4 miles, 91.3 miles into the trip.

I considered driving all the way to VLBW, but decided to call it a day 100.5 miles.

Hopefully, I'll get my car back soon, and will be able take it to VLBC, when I can also get the CW kWh use report.
 
On Saturday I ran another "100%" capacity range test on this same route, with close to 6,000 ft of ascent and descent.

8/18/12 capacity test results:

107.1 miles to VLBW, 108.0 miles in total, by the odometer.

CW reports 105.4 miles (~2.5% under-report) total miles, at 6.2 m/kWh, 17.0 kWh used from 100% to about the same capacity level, slightly past VLBW.

6/17 (Most recent previous) capacity test results:

110.9 miles to VLB, 112.7 in total, by the odometer.

CW: 109.9 (~2.5% under-report) total miles, at 6.3 m/kWh, 17.5 kWh used from 100% to about the same capacity level, slightly past VLBW.

Very similar temperatures, speeds, and driving conditions on these two days. They were separated by only about 1,700 miles, from ~10,016 to ~11,743 miles at the start of the tests, but also by much of the Summer, and several weeks of the highest (by far) ambient temperatures that my LEAF has experienced since delivery.

Compare these two tests 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.

The lower m/kWh on my earlier tests on the "shorter" route, could be entirely accounted for by the route and speed variations.

The apparent loss of ~ 9% of total battery capacity since 9/7/11, plus an undetermined amount of capacity loss over the summer of 2011, prior to my first range test, might indicate I am close to losing a capacity bar...or it might not.

9/10/12 edit-

Below is a screenshot of my CW "Electric Rate Simulation" including this trip on 8/18/12.

8-11-12to8-18-12CWRS.png


Below are the trip profile and map route, both excluding the first and last ~0.3 miles and ~200 ft of descent and ascent on my driveway, that is not mapped by google.

Trips two and three above correspond to the drive to Burney Falls, the second vertical red line (point C on the map image), and the end of the profile and two red lines correspond to the return trip. The extra miles to initiate the VLBW, came from repeating ~ mile 1 to ~ mile 4 on the profile.

MonumentRocktohwy89494mileprofile.png


MonumentRocktoClarkCreekandhwy89rangetestmap.png
 
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