Discuss data from the LEAF Battery app, and Comparisons

[mwalsh]

6/22: AHr=54.07 CAP=81.61%. Mileage: 30,455 miles. Lost bar 12.
6/24: AHr=54.01 CAP=81.52%
6/25: AHr=54.12 CAP=81.68%
7/11: AHr=53.16 CAP=80.23%
7/12: AHr=53.30 CAP=80.45% Hlth=76.57%
8/26: AHr=52.54 CAP=79.30% Hlth=75.16%
9/11: AHr=51.49 CAP=78.49% Hlth=73.22%
10/2: AHr=51.81 CAP=78.98% Hlth=73.82%. Mileage: 34,507
10/8: AHr=51.58 CAP=78.63% Hlth=73.39%. Mileage: 34,813. Lost bar 11.
10/23: AHr=52.12 CAP=79.51% Hlth=74.46%. Mileage: 35,220
11/5: AHr=52.68 CAP=80.31% Hlth=75.43%. Mileage: 35,723
11/12: AHr=52.47 CAP=79.98% Hlth=74.80%. Mileage: 36,071
11/22: AHr=52.74 CAP=80.40% Hlth=75.53%. Mileage: 36,445
11/25: AHr=52.89 CAP=80.63% Hlth=75.81%. Mileage: 36,509
12/22: AHr=52.74 CAP=80.40% Hlth=75.53%. Mileage: 37,596
1/21: AHr=51.38 CAP=78.32% Hlth=73.02%. Mileage: 38,471
2/25: AHr=51.37 CAP=78.31% Hlth=73%
3/12: AHr=50.75 CAP=77.37% Hlth=71.86%
3/24: AHr=51.93 CAP=79.16% Hlth=72.36%. Mileage: 40,228
4/17: AHr=50.81 CAP=77.46% Hlth=71.97%. Mileage: 41,232

5/5: AHr=48.64 CAP=74.15% Hlth=67.96%. Mileage: 41,754

Ruh, roh! Look what last week's hot spell has done to my numbers! Started seeing a fall below 200 Gids for a 100% charge with pretty alarming regularity last week, so I decided to take a set of numbers today instead of leaving it until later in the month. I feel like I'm pretty darn close to loosing bar 10 as it stands right now.

 

[jguenst]

6/22: AHr=54.07 CAP=81.61%. Mileage: 30,455 miles. Lost bar 12.
6/24: AHr=54.01 CAP=81.52%
6/25: AHr=54.12 CAP=81.68%
7/11: AHr=53.16 CAP=80.23%
7/12: AHr=53.30 CAP=80.45% Hlth=76.57%
8/26: AHr=52.54 CAP=79.30% Hlth=75.16%
9/11: AHr=51.49 CAP=78.49% Hlth=73.22%
10/2: AHr=51.81 CAP=78.98% Hlth=73.82%. Mileage: 34,507
10/8: AHr=51.58 CAP=78.63% Hlth=73.39%. Mileage: 34,813. Lost bar 11.
10/23: AHr=52.12 CAP=79.51% Hlth=74.46%. Mileage: 35,220
11/5: AHr=52.68 CAP=80.31% Hlth=75.43%. Mileage: 35,723
11/12: AHr=52.47 CAP=79.98% Hlth=74.80%. Mileage: 36,071
11/22: AHr=52.74 CAP=80.40% Hlth=75.53%. Mileage: 36,445
11/25: AHr=52.89 CAP=80.63% Hlth=75.81%. Mileage: 36,509
12/22: AHr=52.74 CAP=80.40% Hlth=75.53%. Mileage: 37,596
1/21: AHr=51.38 CAP=78.32% Hlth=73.02%. Mileage: 38,471
2/25: AHr=51.37 CAP=78.31% Hlth=73%
3/12: AHr=50.75 CAP=77.37% Hlth=71.86%
3/24: AHr=51.93 CAP=79.16% Hlth=72.36%. Mileage: 40,228
4/17: AHr=50.81 CAP=77.46% Hlth=71.97%. Mileage: 41,232

5/5: AHr=48.64 CAP=74.15% Hlth=67.96%. Mileage: 41,754

Ruh, roh! Look what last week's hot spell has done to my numbers! Started seeing a fall below 200 Gids for a 100% charge with pretty alarming regularity last week, so I decided to take a set of numbers today instead of leaving it until later in the month. I feel like I'm pretty darn close to loosing bar 9 as it stands right now.

I assume you mean 10th bar?

 

[mwalsh]

I assume you mean 10th bar?

Sorry, yes. You're correct. Not enough coffee for me yet this morning.

 

[Weatherman]

Sure looks like a lot of battery replacements are coming for Southern California LEAFs by the end of this year.

I wonder of anyone will admit to crossing the 60,000 mile mark with only 9 bars. Sorry, too late. No new battery for you.

 

[Berlino]

After five and a half months, I was finally able to take the Winter tires off my LEAF. It felt like having a chain removed from neck, the ride with the OEM Michelin Energy Savers is much smoother and quieter than with the Xice X3's from the same manufacturer.

After a brutal Winter, the downside of warm weather is that I'm now losing AHr, Hx, SOH and Gids again. In fact, the rate they're bleeding off is faster than what I experienced last Fall. I'm curious to see where they'll level off. I'll post details later. I'm planning to sell the LEAF in about two weeks and want to give the buyer an accurate idea of the battery's state.

 

[mwalsh]

6/22: AHr=54.07 CAP=81.61%. Mileage: 30,455 miles. Lost bar 12.
6/24: AHr=54.01 CAP=81.52%
6/25: AHr=54.12 CAP=81.68%
7/11: AHr=53.16 CAP=80.23%
7/12: AHr=53.30 CAP=80.45% Hlth=76.57%
8/26: AHr=52.54 CAP=79.30% Hlth=75.16%
9/11: AHr=51.49 CAP=78.49% Hlth=73.22%
10/2: AHr=51.81 CAP=78.98% Hlth=73.82%. Mileage: 34,507
10/8: AHr=51.58 CAP=78.63% Hlth=73.39%. Mileage: 34,813. Lost bar 11.
10/23: AHr=52.12 CAP=79.51% Hlth=74.46%. Mileage: 35,220
11/5: AHr=52.68 CAP=80.31% Hlth=75.43%. Mileage: 35,723
11/12: AHr=52.47 CAP=79.98% Hlth=74.80%. Mileage: 36,071
11/22: AHr=52.74 CAP=80.40% Hlth=75.53%. Mileage: 36,445
11/25: AHr=52.89 CAP=80.63% Hlth=75.81%. Mileage: 36,509
12/22: AHr=52.74 CAP=80.40% Hlth=75.53%. Mileage: 37,596
1/21: AHr=51.38 CAP=78.32% Hlth=73.02%. Mileage: 38,471
2/25: AHr=51.37 CAP=78.31% Hlth=73%
3/12: AHr=50.75 CAP=77.37% Hlth=71.86%
3/24: AHr=51.93 CAP=79.16% Hlth=72.36%. Mileage: 40,228
4/17: AHr=50.81 CAP=77.46% Hlth=71.97%. Mileage: 41,232
5/5: AHr=48.64 CAP=74.15% Hlth=67.96%. Mileage: 41,754

5/21: AHr=48.10 CAP=73.33% Hlth=66.97%. Mileage: 42,485

 

[TomT]

That is where I expect to be: Just shy of an 8BL and a new battery... But if I make it even a month before my lease is up, I'm going to make them replace it!

I wonder of anyone will admit to crossing the 60,000 mile mark with only 9 bars. Sorry, too late. No new battery for you.

 

[mxp]

Consider a tale of 3 2011 Leafs: (we got them all at the same dealer and same week)
2 of which we own (both equal miles, 29K miles), and a friend who lives nearby whose Leaf still have 12 bars (P3227 applied) and have 32k miles.

2011 Silver Leaf (no P3227, QC=13, L1/L2=896)
06/28/13: AHr=58.84 CAP=88.81%. Hlth= n/a
10/25/13: AHr=57.87 CAP=87.87%. Hlth=85.33%
03/10/14: AHr=56.05 CAP=81.61%. Hlth=81.75% (lost 12th bar somewhere in Mar, 2014)
05/11/14: AHr=56.13 CAP=84.69%. Hlth=81.87%
05/18/14: AHr=55.10 CAP=83.16%. Hlth=79.88%


2011 Blue Leaf (no P3227, QC=1, L1/L2=1096)
09/23/13: AHr=57.03 CAP=86.07%. Hlth=83.67%
05/11/14: AHr=55.10 CAP=79.89%. Hlth=85.33% (lost 12th bar somewhere in Mar, 2014)


2011 Friend's Blue Leaf (P3227 applied, QC=13, L1/L2=1465) * mostly L1 (120V charging)
05/20/14: AHr=58.00 CAP=87.54%. Hlth=85.57% (no bars lost)

 

[opencar]

Consider a tale of 3 2011 Leafs: (we got them all at the same dealer and same week)
2 of which we own (both equal miles, 29K miles), and a friend who lives nearby whose Leaf still have 12 bars (P3227 applied) and have 32k miles.

2011 Silver Leaf (no P3227, QC=13, L1/L2=896)
06/28/13: AHr=58.84 CAP=88.81%. Hlth= n/a
10/25/13: AHr=57.87 CAP=87.87%. Hlth=85.33%
03/10/14: AHr=56.05 CAP=81.61%. Hlth=81.75% (lost 12th bar somewhere in Mar, 2014)
05/11/14: AHr=56.13 CAP=84.69%. Hlth=81.87%
05/18/14: AHr=55.10 CAP=83.16%. Hlth=79.88%


2011 Blue Leaf (no P3227, QC=1, L1/L2=1096)
09/23/13: AHr=57.03 CAP=86.07%. Hlth=83.67%
05/11/14: AHr=55.10 CAP=79.89%. Hlth=85.33% (lost 12th bar somewhere in Mar, 2014)


2011 Friend's Blue Leaf (P3227 applied, QC=13, L1/L2=1465) * mostly L1 (120V charging)
05/20/14: AHr=58.00 CAP=87.54%. Hlth=85.57% (no bars lost)

are you guessing it's the P3227 causing the difference or the L1 charging (or some other difference between your friend & your usage)?

 

[Weatherman]

July 11th: 57.45 Ahr
Aug 12th: 56.30 Ahr
Sept 10th: 55.46 Ahr
Oct 23rd: 54.61 Ahr
Nov 4th: 54.26 Ahr
Dec 10th: 53.86 Ahr
Jan 25th: 53.06 Ahr

May 21st: 52.36 Ahr


A bit of a gap between the last two reports. Capacity held relatively steady, around 52.80, during February and March, but began falling rapidly, again, in April. With battery temps back in the 90s, I'd expect to lose the 10th bar within the next two months. 9th one may be gone by the end of 2014.

I'm counting down the days to turn the car back in to Nissan. I don't think I'll hold onto it after Memorial Day next year.

 

[mxp]

Consider a tale of 3 2011 Leafs: (we got them all at the same dealer and same week)
2 of which we own (both equal miles, 29K miles), and a friend who lives nearby whose Leaf still have 12 bars (P3227 applied) and have 32k miles.

2011 Silver Leaf (no P3227, QC=13, L1/L2=896)
06/28/13: AHr=58.84 CAP=88.81%. Hlth= n/a
10/25/13: AHr=57.87 CAP=87.87%. Hlth=85.33%
03/10/14: AHr=56.05 CAP=81.61%. Hlth=81.75% (lost 12th bar somewhere in Mar, 2014)
05/11/14: AHr=56.13 CAP=84.69%. Hlth=81.87%
05/18/14: AHr=55.10 CAP=83.16%. Hlth=79.88%


2011 Blue Leaf (no P3227, QC=1, L1/L2=1096)
09/23/13: AHr=57.03 CAP=86.07%. Hlth=83.67%
05/11/14: AHr=55.10 CAP=79.89%. Hlth=85.33% (lost 12th bar somewhere in Mar, 2014)


2011 Friend's Blue Leaf (P3227 applied, QC=13, L1/L2=1465) * mostly L1 (120V charging)
05/20/14: AHr=58.00 CAP=87.54%. Hlth=85.57% (no bars lost)

are you guessing it's the P3227 causing the difference or the L1 charging (or some other difference between your friend & your usage)?

Indeed we were also pondering the exact same questions. I hope someone here on the forums can share some light on this.

The Friend's Blue Leaf (1465 cycles) are 95% all purely L1 (120V) charging/top-ups etc.

All 3 vehicles are acquired from Boardwalk, all our VINs are ....46xx. Our cars are pretty much same manufacture batch, similar mileage, commute locations similar (flat surface) and location temps are the same. The only difference is how we charge the cars.

I hope someone can find some nuggets of learning from this data.

More info:
All 3 cars do 40-50 mile commutes per day.
My Silver Leaf has a erratic commute schedule. Some days I drive some days I don't but the mileage is the same with the other Blue Leaf.
My other Blue Leaf has a strict Mon, Wed, Friday routine commute which sees 100% L2 charging on those days. Mainly gets almost no charge cycles or driving on weekends.

 

[Pipcecil]

ok, I am wondering if anyone can figure this one out. Today I started off with three bars missing and an AHr value of 43.14 (65%). I QC'd twice, once to 80% and once to almost full (98% on the QC display) plus a level 1 until 90%ish in between. The entire time all three bars. Drive home, using most of the battery (30sih miles), stop to get dinner 10 miles away from home and when I hop back into the car, my fourth bar went away. I only noticed it while I was driving so I quickly turned on leaf spy - my AHr had jumped from 43.14 to 43.32. I don't understand how my AHr could jump that much with that much charging (and increasing my battery temp from 95 to 105). In addition why did I loose my bar AFTER my AHr jumped by 18 units? Why didn't it drop when it was at it's lowest? Anyone venture a guess?

 

[TimLee]

... In addition why did I loose my bar AFTER my AHr jumped by 18 units? Why didn't it drop when it was at it's lowest? Anyone venture a guess?

Bit unclear what algorithm Nissan uses for capacity bars but bars loss can vary a lot.
May be due to long term average. But also may tie more strongly to health rating and internal resistance. I lost my first bar fairly early, but had done a lot of quick charge. Did much less quick charge the last nine months and second bar hasn't fallen yet. Although LEAF Spy Pro indicates I am close.
The two quick charges and 105 F temp probably helped cause fourth bar loss in time for capacity warranty assuming you didn't Opt Out and had your annual battery tests in a timely manner.
Good luck with battery replacement and wishing you luck on getting the heat resistant chemistry.
Nissan put you through a lot of poor treatment on that on board charger failure.
You deserve a break

 

[lorenfb]

"But also may tie more strongly to health rating and internal resistance."

It might be interesting to have the battery "internal resistance" data as a function bar loss.
For those that have the LeafDD, that data can be easily determined:

(http://www.mynissanleaf.com/viewtopic.php?f=44&t=12561&start=310#p371789" onclick="window.open(this.href);return false:

The LeafDD is useful to determine another proxy for battery condition.
A typical battery condition evaluation is a load test, which basically
measures the output impedance of the battery.

Since the LeaffDD can display simultaneously both the Leaf's instantaneously
battery voltage and current, the instantaneous output impedance can then be
determined. Obviously, the output impedance will vary as the battery becomes
discharged. As a result, any evaluation over time should be done at the
same charge level of the battery. This method is not to be considered as a
rigorous and robust calculation of output impedance, but as a quick and simple
method to evaluate the Leaf's battery condition over time.

As an example:

Mileage - 7600, Charge Level - 50Ahr, Temp - 76 deg, Speed ~ 30 MPH
Load ~ 64 amps (25% of FS from acceleration), Voltage Change ~ 4 volts

Then Z (out of battery) = 4 volts / 64 amps ~= 62.5 milli-ohms or 16 mhos

 

[GregH]

I've actually seen much more variation on impedance based on pack temperature than SOC.. although maybe I've just been watching that more. Chemistry is inherently more efficient (lower impedance) at higher temps. A company I consulted for used battery voltage exclusively for their SOC calculations with a slow filter and compensation for current based on an assumed impedance. These batteries (made of 2Ah 18650s) didn't have nearly as much capacity fade with age as the Leaf, but they did have greatly increased impedance. I did a number of tests at various temperatures to show them how big a component the temperature was as well.

As for the 4th bar loss (sorry to hear) as others have noted there looks like a huge hysteresis on the bar loss algorithm. Likely below some trigger Ah capacity (43.4? 43.5?) for many days or weeks before the trigger is pulled. By my math 43.3Ah is less than 70% of original capacity.. ouch.. that sucks.

 

[Pipcecil]

I've actually seen much more variation on impedance based on pack temperature than SOC.. although maybe I've just been watching that more. Chemistry is inherently more efficient (lower impedance) at higher temps. A company I consulted for used battery voltage exclusively for their SOC calculations with a slow filter and compensation for current based on an assumed impedance. These batteries (made of 2Ah 18650s) didn't have nearly as much capacity fade with age as the Leaf, but they did have greatly increased impedance. I did a number of tests at various temperatures to show them how big a component the temperature was as well.

As for the 4th bar loss (sorry to hear) as others have noted there looks like a huge hysteresis on the bar loss algorithm. Likely below some trigger Ah capacity (43.4? 43.5?) for many days or weeks before the trigger is pulled. By my math 43.3Ah is less than 70% of original capacity.. ouch.. that sucks.

That does make some sense - as the temperature rises, the battery gets "looser" and is able to hold more - although I always thought that happened as it got colder (but the colder temperature makes the existing capacity less efficient even though more battery is available). I have tracked my AHr since January and never saw am increase this quick in one day, so it just really surprised me. I was on a steady trend downward and had reached this value previously a week and a half ago, so it was pretty confusing to me since it wasn't associated with a cold front or an outside drop in temperature - the usual stuff that causes an increase.

My thought was the BMS - the car set the AHr value once it lost the 4th bar. Maybe the capacity was "drifting" similar to the day-to-day battery state of charge drifts a bit while driving (because of the inaccurate way they measure it) and rights itself after you turn off and start up again. Maybe once the bar was lost it was able to correct the slow drift in the capacity loss? Hmmm..

Well, despite the 4 bars gone, this means I get to replace the battery, YEA! SO I am really excited about that. I am tired of a 50 mile range to turtle and can't wait for 85 miles again (assuming I get a new battery).

 

[lorenfb]

- GregH -

"I've actually seen much more variation on impedance based on pack temperature than SOC.. although maybe I've just been watching that more. Chemistry is inherently more efficient (lower impedance) at higher temps. A company I consulted for used battery voltage exclusively for their SOC calculations with a slow filter and compensation for current based on an assumed impedance. These batteries (made of 2Ah 18650s) didn't have nearly as much capacity fade with age as the Leaf, but they did have greatly increased impedance. I did a number of tests at various temperatures to show them how big a component the temperature was as well."

As with a any battery, its open-circuit voltage and its short-circuit current characterize its impedance
and thus its output/capacity over time. A number of published papers corroborate this relationship:

I. Experimental investigation of the lithium-ion battery impedance characteristic at various conditions and aging states and its influence on the application by Waag, Wladislaw (Electrochemical Energy Conversion and Storage Systems Group, Institute for Power Electronics and Electrical Drives (ISEA) and Institute for Power Generation and Storage Systems (PGS) - E.ON ERC, RWTH Aachen University (Germany)); Käbitz, Stefan; Sauer, Dirk Uwe (Electrochemical Energy Conversion and Storage Systems Group, Institute for Power Electronics and Electrical Drives (ISEA) and Institute for Power Generation and Storage Systems

Abstract: In recent years, lithium-ion batteries have often been proposed as part of various hybrid energy systems. Examples of such applications are hybrid vehicles, photovoltaic-battery or wind-battery systems and power distribution grids. The power capability of the battery is described by its impedance characteristic. It depends significantly on the battery state-of-charge (SoC), the temperature, the current and the previous history. In this paper, these dependencies and their variations over the battery lifetime are investigated on a 40 Ah lithium-ion cell produced by Kokam with nickel manganese cobalt oxide (NMC) cathode material as an example. The results obtained for the new and aged states are compared. The results show, for example, that the SoC range, in which the battery operates with high efficiency, decreases due to significant aging. For the first time, the nonlinearity (current dependency) of the battery resistance is investigated extensively. It varies slightly with the SoC and considerably with the temperature, and it also changes during the battery lifetime. Furthermore, the dependency of the lithium-ion battery impedance on the short-time previous history is shown for the first time for a new and aged cell.

II. Quick testing of batteries in lithium-ion battery packs with impedance-measuring technology
Authors:

Takeno, Kazuhiko; Ichimura, Masahiro; Takano, Kazuo; Yamaki, Junichi; Okada, Shigeto

Publication: Journal of Power Sources, Volume 128, Issue 1, p. 67-75.
Publication Date: 00/2004
Origin: ELSEVIER

Abstract
We discuss a rapid testing of capacity in Li-ion battery packs with impedance-measuring technology to evaluate their capability in mobile phones. Our measurements of the capacity and impedance at 1 kHz for various kinds of battery packs conclusively proved that there is a strong correlation between capacity and impedance. It can be applied even when the pack consists of not only a Li-ion battery but also a Positive Temperature Coefficient (PTC) device and a protection circuit in-series, and this correlation is largely unaffected by the degree of charge. The results we obtained from measuring impedance revealed the possibility of quickly assessing degradation in Li-ion battery packs.

There're a number of other papers presenting similar data correlating capacity and impedance not
presented here.

Therefore, one might expect to find that the Leaf's AHr rating over time based on; average battery temp,
cycling, and age would have a negative correlation coefficient with the battery impedance. And as such,
its impedance being a reliable proxy for battery capacity.

 

[TickTock]

I've actually seen much more variation on impedance based on pack temperature than SOC..

Yup. The noise in the Resr plot does correlate somewhat to SOC (left out of the graph for clarity), but the pack temperature has the largest influence. Also, we had been wondering if maybe Hx was related to resistance, and from the data I've gathered over the last few months, it doesn't look like the case.

 

[lorenfb]

I've actually seen much more variation on impedance based on pack temperature than SOC..

Yup. The noise in the Resr plot does correlate somewhat to SOC (left out of the graph for clarity), but the pack temperature has the largest influence. Also, we had been wondering if maybe Hx was related to resistance, and from the data I've gathered over the last few months, it doesn't look like the case.

How is this "resistance" being measured and/or determined? And what are the units of measure?
Neither of these have been indicated in the post nor on the graph. And what device was used that
provided the data?

 

[GregH]

It kinda sucks.. If we could keep the battery at 0-10 degrees it would last forever but perform rather poorly. If we could keep the battery at 40-50 degrees it would be much more efficient but crap out in a matter of months (as our desert friends witness). 20 degrees seems to be a happy medium for the Leaf. The battery is still relative low impedance but the Ah cap doesn't drop noticeably on a daily basis.

I really have no idea how the Ah capacity number in the BMS is calculated. It seems that every now and then the BMS wakes up, looks at the temp, and deducts a few mAh based on how high the temp is. Even with no cycling I've seen the number change... Other than the clock itself, what else could they be looking at?!?! Normally I would expect capacity adjustments based on charge or discharge events (say for example hitting 3.7v/cell at an earlier or later SOC than expected.. Or similar on charging). But the current sensor on the Leaf is so crappy they can't really rely on Ah counting so there must be constant readjustments based on voltage. Sometimes just sitting there I've seen my current sensor show small charge and the SOC drift up... No, you can't charge from the ether...

I still see a direct relationship between Ah cap and Hx... Even post SW update.

LeafDD looks at Voltage delta at high current during select high current events and notes the SOC and temp at the time of the test (milliohms result). CANary constantly looks at the voltage current relationship to give a somewhat continuous readout of the impedance at the time.