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TickTock
Posts: 1701
Joined: Sat Jun 04, 2011 10:30 pm
Delivery Date: 31 May 2011
Leaf Number: 3626
Location: Queen Creek, Arizona
Contact: Website

Re: 20% capacity loss in 9 months is "normal"

Sat Mar 24, 2012 8:23 pm

Stoaty wrote:After re-reading this thread, I am going to change my stance a bit:

1) It appears that you Gid count was low from the start, though oddly has risen with time. I would say that your car has a 9.3% loss (255/281) over 9 months, which I would consider high. Mine is at 269 Gids (4.3% loss) after a full charge after 9 months of use (but I have fewer miles). From what I have seen on the forum so far, I would say my Gid count is at the lower end of "normal" for the Leaf.

2) I don't think you can use the miles remaining on the GOM to conclude anything, especially since the demo Leaf may have the updated GOM estimates.

3) As I found out when testing my Leaf, you have to drive the Leaf through a very large part of its range in order to get true capacity. In that regard, how many miles is your commute, what is the miles/kWh for your commute (on the dash), and what is your typical starting and ending Gid count? My guess is that you will still be an outlier, but I doubt this will show a 20% loss.

wrt#2: My Leaf got the latest update prior to the test so it is apples to apples. None-the-less, I agree the GOM isn't the best means to determine capacity. I was frankly surprised that this was the only tool in the dealer arsenal to determine capacity. Why they don't have kWh meters on their chargers or read the available charge (gids) is mind-boggling. The "
conscious" Leaf owner with gary's SOC meter, it seems, has] more information than the technicians at the dealer.
[edit:corrected grammar]
Last edited by TickTock on Sat Mar 24, 2012 9:09 pm, edited 1 time in total.

smkettner
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Location: Orange County, CA

Re: 20% capacity loss in 9 months is "normal"

Sat Mar 24, 2012 8:36 pm

I think I would commit three hours and drive the car in best possible conditions for 80 to 90 miles before you panic about capacity.
1 bar lost at 21,451 miles, 16 months.
2 bar lost at 35,339 miles, 25 months.
LEAF traded at 45,400 miles for a RAV4-EV

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Boomer23
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Location: Orange County, CA

Re: 20% capacity loss in 9 months is "normal"

Sat Mar 24, 2012 9:06 pm

Just to add some data to the discussion, my LEAF #889 was delivered March 30, 2011, almost 12 months ago. It has 11,049 miles at this moment. I have had one of Gary's SOC meters for months, since September IIRC. I charge to 100% routinely and I have logged gids upon first drive each day and at end of day for months. I've been getting 281 gids repeatedly, in fact 6 times out of 13 full charges that I have documented in March were to 281 gids, and 5 more charges were no lower than 278 gids. So I think that I have full capacity at the same total mileage as Tick Tock, and I'm ignoring Nissan's "long life" recommended charging schedule of 80% charging.

If I can be of any help in providing gid data from my car, please let me know.
2014 BMW i3 with Range Extender
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garygid
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Leaf Number: 000855
Location: Laguna Hills, Orange Co, CA

Re: 20% capacity loss in 9 months is "normal"

Sat Mar 24, 2012 9:38 pm

If Nissan's official diagnosis is that your LEAF has "lost"
(or never had) over 19% of its new capacity, perhaps ask
Nissan to fix your car's "defective" Capacity-Bars meter?
See SOC/GID-Meter and CAN-Do Info
2011 LEAF, sold in 2015
2010 Prius, 2014 silver Tesla S
Nissan EVSE, mod to 240/120v 16A
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drees
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Re: 20% capacity loss in 9 months is "normal"

Sat Mar 24, 2012 11:20 pm

smkettner wrote:I think I would commit three hours and drive the car in best possible conditions for 80 to 90 miles before you panic about capacity.

I do believe that TickTock has done this before, but certainly if it were my car I'd be curious and run this test:

1. Charge to 100% and let the car sit at least 4 hours on the charger.
2. Record GIDs/Volts
3. For good measure, top it off before departure in case the car didn't automatically top-off after balancing and record GIDs/Volts after done.
4. Hit the road at a fairly constant speed on a well known out-and-back loop with the goal of getting home around LBW. Aim for highway between 55-65 mph.
5. Record distance, economy (mi/kWh) and GIDs at LBW.
6. Optionally drive around a bit longer until VLBW and record distance, economy.
7. Charge back to 100% and record the amount of energy used to charge back to 100%.

Report back!

Given your 100% GID counts appear to be around 92% of "full" (281), I'd expect you to log about 92% the distance one might otherwise expect.

Some other comments:

The reported "20%" loss came from the dealer comparing the GOM readout of two cars - we all know how unreliable this can be even with very slight differences between drives. For example, I can get home after my daily commute of ~25 miles with the same mi/kWh and have GOM readings over 10 miles different.

It certainly seems that people who frequently charge to 100% seem to also seem to consistently have higher GOM readings. I think this is either due to BMS calibration or battery balancing.

One common method of forcing a recalibration is to drain the battery and then do a full charge (unsure if this will trigger it on the LEAF). If you wish to avoid the risk of stranding yourself, the service manual recommends running the heater on max temp with the windows open in a well ventilated area. Do this until turtle engages or power bubbles start disappearing and charge to 100% - record energy consumed in the charge to help confirm battery capacity!

So far the only known way to make sure that the pack balances itself is to charge to 100% and let the car sit for at least 4 hours before taking it off the charger.
'11 LEAF SL Powered By 3.24 kW Enphase Solar PV

vegastar
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Joined: Mon Dec 13, 2010 11:29 am
Delivery Date: 07 Jul 2011
Leaf Number: 5564
Location: Portugal

Re: 20% capacity loss in 9 months is "normal"

Sun Mar 25, 2012 1:46 am

Regarding the CVLI, I think the 0.06V difference between the highest and lowest cell could explain some of the low capacity if:

- the pack is balanced
- the lowest voltage cell is an outlier
- the highest voltage cell is not an outlier

Do you know the total pack voltage when the CVLI was done?
2011 Nissan LEAF since 2011-07-07, 87000 km on 2015-02-28. 10 bars, 182gids@80%charge, 51.7Ah.

Herm
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Location: Timbuktu, Mali

Re: 20% capacity loss in 9 months is "normal"

Sun Mar 25, 2012 5:39 am

drees wrote:I do believe that TickTock has done this before, but certainly if it were my car I'd be curious and run this test:


Why bother?.. Perhaps back a few months ago when we had no tools, but now we have GID meters and it shows his battery is 9% below normal, probably from day one and probably just one* of the modules.. since all the modules are in series the weakest one determines the total pack capacity.

The question I would be interested in is how stable is this module. A bit more degradation and his first capacity bar will light off.




*I'm always an optimist, but it could be anything, from a bad connector to a blown out cell. It could also be perfectly normal cell manufacturing variability or calibration. No two cells are exactly alike. Dont forget your GID meter when you pick up your new Leaf.

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RegGuheert
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Location: Northern VA

Re: 20% capacity loss in 9 months is "normal"

Sun Mar 25, 2012 6:34 am

vegastar wrote:Regarding the CVLI, I think the 0.06V difference between the highest and lowest cell could explain some of the low capacity if:

- the pack is balanced
- the lowest voltage cell is an outlier
- the highest voltage cell is not an outlier
I think this is an important point. If all of these conditions are true, which is the worst case for cell 25, then you can expect that cell 25 will receive quite a severe overcharge whenever the pack is charged to 100%, which should greatly shorten its life. (This assumes that the Leaf does not actively shunt it during charge in order to protect it. I seriously doubt they are doing something like that.). As a result I would expect this module will need to be replaced sometime within the warranty period.

I guess I don't see an issue with Nissan's response, so far. IMO, one of the beauties of the design of the Leaf battery system is that individual modules can be replaced. They have publicly discussed that they expect this will be necessary in some cases, but that replacement of the entire pack should not be necessary in most cases. In TickTock's case, he can expect this cell to degrade within the next year or so to the point at which Nissan's service computer will recommend replacement during one of the annual inspections. At that point, he should receive a new module which will likely have the same or higher capacity than the rest of the pack, which is not an issue.

BTW, I recently purchased a demo Leaf and just yesterday had a very similar excursion to the one which TickTock described in the OP. GOM was reporting 43 miles and five bars were left after driving only 32 easy miles starting from 80% charge. As such, I can certainly relate to being concerned about battery capacity. But I also see this EV campaign by Nissan as EXTREMELY high profile. They are gearing up to sell massive quantities of these cars. I am quite hopeful that they will not leave us at the end of our 8-year warranty with only 50% battery capacity!
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
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edatoakrun
Posts: 4704
Joined: Thu Nov 11, 2010 9:33 am
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Leaf Number: 2184
Location: Shasta County, North California

Re: 20% capacity loss in 9 months is "normal"

Sun Mar 25, 2012 7:29 am

IMO, the most accurate and comprehensive calculation of battery capacity, can (presently) be accomplished by range tests, from 100% charge, to the lowest level your situation allows. Shortly after I got my leaf, I chose a trip I knew I would want to make repeatedly, near maximum range.

By reducing variations under my control, speed. driving style, and climate control, as much as possible, and recording variations in available battery capacity, energy use and efficiency outside my control, principally (estimated) battery temperature, and driving temperature, I believe I now have a baseline record of maximum range, allowing me to calculate any reduction, in the future.

I’ve repeated the process several times, and, since having CW updated in August, I believe I am able to not only record the range experienced on this drive, but am also able to calculate available battery capacity, with reasonable accuracy. For example, last September:

...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....

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.
So, from the limited info I can gather, looks to me that Carwings may now be accurate as to energy use.

Posts from others who can take the charge lower could verify this...


viewtopic.php?f=31&t=5423&hilit=carwings+update&start=10

Of course, if you feel you have more accurate means of calculating available battery capacity from range, than Carwings, you could use those methods.

I would suggest Every LEAF owner try this. At least until some point in the Future, when Phil, or others, may provide more accurate methods.

But IMO, every LEAF owner should be able get resolution to +/- a few percent, by doing this. You will also see for yourself how variations in temperature, ECO/drive, use, braking, etc., affect your energy use, and how effectively ascent energy is recovered, in descent.

It could also be very useful to have this information, if there is ever a difference of opinion between yourself, and Nissan as to your present or past battery capacity, such as may be so, in this case.
no condition is permanent

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garygid
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Re: 20% capacity loss in 9 months is "normal"

Sun Mar 25, 2012 8:20 am

If a cell-pair is low (high) when the pack is low AND low (high) when the pack is high, the c-p is out of balance.
However, if it is low when the pack is low, and high when the pack is high, the c-p has LOW capacity.

One needs two cell voltage tests to detect this condition (one at high charge and one at low change).
See SOC/GID-Meter and CAN-Do Info
2011 LEAF, sold in 2015
2010 Prius, 2014 silver Tesla S
Nissan EVSE, mod to 240/120v 16A
PU: SDG&E
Solar PV: 33 x 225W -> 7 kW max AC
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