edatoakrun
Posts: 5222
Joined: Thu Nov 11, 2010 9:33 am
Delivery Date: 15 May 2011
Leaf Number: 2184
Location: Shasta County, North California

Use CW report from range test to determine battery capacity

Mon Jun 04, 2012 11:11 am

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.p ... e&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.

Image

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.p ... 1&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.


Image

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

Image
Last edited by edatoakrun on Wed Aug 01, 2012 7:21 am, edited 3 times in total.
no condition is permanent

edatoakrun
Posts: 5222
Joined: Thu Nov 11, 2010 9:33 am
Delivery Date: 15 May 2011
Leaf Number: 2184
Location: Shasta County, North California

Re: Range test-determine initial/reduced LEAF battery capaci

Wed Jun 20, 2012 9:15 am

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.
no condition is permanent

Herm
Posts: 3765
Joined: Sun May 23, 2010 3:08 pm
Delivery Date: 29 Aug 2012
Location: Timbuktu, Mali

Re: Range test-determine initial/reduced LEAF battery capaci

Wed Jun 20, 2012 9:44 am

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.

edatoakrun
Posts: 5222
Joined: Thu Nov 11, 2010 9:33 am
Delivery Date: 15 May 2011
Leaf Number: 2184
Location: Shasta County, North California

Re: Range test-determine initial/reduced LEAF battery capaci

Wed Jun 20, 2012 9:59 am

Herm wrote: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.
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TonyWilliams
Posts: 10091
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Location: San Diego
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Re: Range test-determine initial/reduced LEAF battery capaci

Wed Jun 20, 2012 2:17 pm

Herm wrote: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.

Herm
Posts: 3765
Joined: Sun May 23, 2010 3:08 pm
Delivery Date: 29 Aug 2012
Location: Timbuktu, Mali

Re: Range test-determine initial/reduced LEAF battery capaci

Wed Jun 20, 2012 4:16 pm

TonyWilliams wrote: 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.

SanDust
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Re: Range test-determine initial/reduced LEAF battery capaci

Wed Jun 20, 2012 8:26 pm

TonyWilliams wrote: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.

LEAFfan
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Re: Range test-determine initial/reduced LEAF battery capaci

Wed Jun 20, 2012 8:55 pm

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.
2013 LEAF SV Del. 2/28/13
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TonyWilliams
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Location: San Diego
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Re: Range test-determine initial/reduced LEAF battery capaci

Wed Jun 20, 2012 9:50 pm

SanDust wrote:
TonyWilliams wrote: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.

SanDust
Posts: 1363
Joined: Fri Aug 06, 2010 10:54 am

Re: Range test-determine initial/reduced LEAF battery capaci

Fri Jun 22, 2012 11:29 am

TonyWilliams wrote: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!

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