12% capacity loss in 9 months is "normal"

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Stoaty said:
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]
 
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.
 
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?
 
smkettner said:
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.
 
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?
 
drees said:
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.
 
vegastar said:
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!
 
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...

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

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.
 
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).
 
Nissan needs to fix this particular car (replace battery / cells etc). Nobody would want to buy a car where 20% capacity loss in the first year is "normal".
 
garygid said:
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.

If you have a low capacity module it will be charged to 100% along with all the modules, and balanced at that point only if needed.. once you start driving that low cap module will hit the low voltage limits first and force the car into turtle, while all the other modules still have 9% charge remaining.. once you recharge all the modules are brought back up to 100% without a need for rebalancing. The weakest link in the chain determines the overall pack capacity.
 
RegGuheert said:
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.

Reg,

Congrats on your new car. I'm not sure how much you've followed along on here prior to your purchase, but nobody puts much thought into what the GoM says. Personally, I cover the thing, since bad data (to me) is worse than no data.

The only true method to determine how far your car will go is to actually drive the car from 100% to Turtle. The important parameters to consider are listed in the notes in the bottom of the range chart (link in my signature line).

If you ever think your battery is experiencing an abnormality, as previously suggested in the thread, try to duplicate a test drive in the same conditions (and preferably course) that you test drove when you bought the car. That means you have to make this run now, and then compare it to that same run in the future when you suspect an abnormality. You should always use climate control off, as there are too many variables there, and I suggest as level highway as can be found in your area.

Temperature is easy to match, but an important note is BATTERY temperature. If you just used a DC quick charger 6 times in a row, and the ambient air is 55F, your battery might be 120F.

Conversely, if your car is left sitting outside in the freezing cold overnight, but it's now 70F in the afternoon, your battery is not at 70F. This is a typical southern California winter weather pattern.

So, the baseline run when your car is new (and record all the data for future use) and a subsequent future run when you suspect a battery abnormality later needs similar battery temperature, ambient temperature (it's important to match up air density at the same elevation), same level terrain if possible (level terrain and steady speed will eliminate the variables of regeneration, because there won't be any), no heater or a/c (for hopefully obvious reasons), the same vehicle weight and dry road conditions. The end result should give you a baseline to compare your performances to consider battery degradation. Some great tools for data collection are Gidmeter or LEAFscan tools !!!

Some more notes to gather your baseline range data; you want a road where you can maintain a steady speed. To compensate for any wind and to compensate for elevation variations (you absolutely will be returning to the same elevation when you pull back in your driveway at the end of the test), I recommend 40-ish miles out, and return of 40-ish miles in the opposite direction, all at 60mph. If you can't travel at 60mph, match whatever speed you use with your estimated range; for example, 50mph steady speed can go about 97 miles per the range chart, so drive outbound about 45-47 miles before turning around for the return.

You need to reset your odometer and miles/kWh economy meter on the dash at the beginning of your run, but don't reset this data until you've collected the data at the end of the test. You should use the Nav economy meter (which reads 0.1 high with the present firmware) to get steady speed data. Get your car at the stable target speed (again, let's choose 60mph) and then reset the Nav economy meter while at that target speed to (hopefully) get the target miles/kWh at that speed. For instance, while on the outbound 40-ish mile leg, at 60mph with cruise control, hit reset on the Nav economy screen reset, and at the end of a continuous 40-ish miles while still at 60mph, expect to see 4.0 miles/kWh on that meter before you start slowing down to reverse course. Then subtract 0.1 to match the console date, to get 3.9 miles/kWh.

Then do the same on the return run. Get to speed, then reset Nav economy gauge, and read the result at the end BEFORE you change the speed. Again, if there's any wind, or elevation changes, or both, you'll get two different numbers for each direction. Again, do not reset the dash economy meter until you've recorded that data for the entire trip, from 100% charge to Turtle mode. Naturally, the dash miles/kWh number won't match your two way averaged 60mph Nav data (even when corrected -0.1), since you weren't driving 60mph the entire trip, like in your driveway, and through the neighborhood to the highway that your test was conducted on.

Its not so important to note fuel bars (but you can) as they are a variable In energy capacity per unit (but not as crazy as the GoM). For instance, the fuel bars will show 12 units at "100%" charge, even if the battery is -20C with 50% degradation. Important "hard data" landmarks are the mileage readings at Low Battery Warning, Very Low Battery, and subsequently Turtle. You don't need to drive the car to dead, just Turtle mode.

Check the tire pressure before a run! 36psi is recommended, many of us run right up to the 44psi limit specified by the tire manufacturer. Reset both economy meters and odometers. Do not attempt this on windy days. Do NOT use the GoM (that's just dumb) or CarWings (current firmware is off 2.5% for mileage).

BALANCE THE BATTERY CELLS FIRST!!! That means, charge to 100% and let the car sit for 4 hours after the car reaches 100% while still plugged in. Or, if you observe a top off charge between one and four hours after reaching 100%, you can then consider the cells balanced (as much as is possible). You don't have to do anything else. The LEAF's automation will take care of all the dirty work.

Data to record:

1. Any changes to car from stock (different tires, bike rack, Texas cattle horns, etc)
2. Tire pressures set, heater and air conditioning off, car at 100% charge, cells allowed time to balance
3. Gross vehicle weight? 3350 pounds plus operator, passengers, spare tire, bags, concrete, etc
4. Route, length, elevation, hills if any, general conditions (dry, concrete/asphalt, etc)
5. Assumed or measured battery temp (from LEAFscan tool)
6. Ambient air temp
7. Gid count at start, if available
8. SOC, if available (from LEAFscan)
9. Starting total voltage (should be 393.5v from GidMeter or LEAFscan tools)

Now, the run data:

1. Outbound steady speed (confirm with cruise control on)
2. Outbound observed steady speed miles/kWh from Nav adjusted -0.1
3. Inbound steady speed (confirm with cruise control on)
4. Inbound observed steady speed miles/kWh from Nav adjusted -0.1
5. Miles at Low Battery Warning
6. Miles at Very Low Battery
7. Overall miles covered to Turtle
8. Overall miles/kWh from dash economy display
9. Calculated battery useable energy (miles / miles/kWh = battery kWh)
10.Ending pack voltage, SOC, and Gid (350v-ish from GidMeter or LEAFscan tools)

Post all this data on here for our crack team of LEAFers to decode, but plug the car in to recharge first!

Tony
 
TonyWilliams said:
RegGuheert said:
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.

The only true method as to how far your car will go is that 100% to Turtle test. The important parameters to consider are listed in the notes in the bottom of the range chart (link in my signature line).

+1.

Tony,

Why don't you make this post in to a new "how to check your battery capacity / full range" thread and I'll sticky it.
 
evnow said:
Tony,

Why don't you make this post in to a new "how to check your battery capacity / full range" thread and I'll sticky it.

Ok, I'll do that with the expanded version.

http://www.mynissanleaf.com/viewtopic.php?p=184814#p184814" onclick="window.open(this.href);return false;
 
After reading through this thread I am having a thought… a charger problem??? I am wondering if this could be an overlooked cause of your lower state of charge.

Do you have the QC port? Could you do a QC and then read your gids? I believe a QC completely bypasses the onboard charger.

Would someone with a bit more experience or knowledge with the communication between the BCM and charger comment about the possibility of a charging issue?
 
Herm said:
garygid said:
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.

If you have a low capacity module it will be charged to 100% along with all the modules, and balanced at that point only if needed.. once you start driving that low cap module will hit the low voltage limits first and force the car into turtle, while all the other modules still have 9% charge remaining.. once you recharge all the modules are brought back up to 100% without a need for rebalancing. The weakest link in the chain determines the overall pack capacity.

I think it makes sense that the procedure to identify bad cells only looks at the voltage at near full discharge. Since the charge controller performs cell balancing, we can assume that even if this cell was the weak link (and hit the peak voltage first during charging) it would then have been discharged to allow the other cells to finish filling up. This would, of course, result in this cell hitting the min voltage first when you discharged the pack. Since the slope of voltage vs. charge is largest when near full discharge, this is the best condition to look at all the cell-pair voltages.

The 60mV max-min cell-pair voltage implies I really don't have a single bad cell. Looking at the battery voltage versus gids curve(http://www.mynissanleaf.com/viewtopic.php?f=31&t=6116&hilit=turtle+dead&start=79), it appears the slope near VLBW is about 6V/gid or 6/96=62.5mV_per_cell/gid. Call it 60; so even if all my cells were matched to the highest (and could discharge all 96 an additional 60mV), that would only buy me 80wH. I think this means that my entire pack is degraded and it's not a matter of replacing a single cell. This is particularly alarming. Not only is Nissan not standing behind their battery capacity it appears the claim that repair costs will be low because you will only have to replace once cell is wishful thinking.

[Edit: clicked submit too soon, had unfinished sentences]
 
jamesanne said:
Do you have the QC port? Could you do a QC and then read your gids? I believe a QC completely bypasses the onboard charger.

An excellent suggestion. We're so focused on the bad battery, we may have overlooked something quite simple.
 
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