Capacity Loss on 2011-2012 LEAFs

TickTock said:

Not sure about the Nissan pack chemistry, but many batteries are endothermic during discharge (will actually absorb heat) and exothermic during charging. I suspect this is the case for the Leaf pack since you saw a large rise in temperature during charging and a very small rise during driving (which typically pulls more power then charging). This could also explain why they limit the regen to 20kW but will let you have 80kW for accelleration.

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I believe it is the charge phase that can be partially endothermic, not discharge, based upon this report I first posted in another thread:
http://www.micro-power.com/userfiles/file/mp_tempcharge-1250026530.pdf

As stated in this report, the endothermic chemistry can be dominated by ohmic losses in the copper conductors, explaining the heating we have seen with QC.

In applying the t^.5 dependence for the time-dependent loss component as mentioned by Stoaty on pg 65 and others, taking Sqrt(years) is not necessarily right. It depends upon where the "knee" in the curve occurs, the point at which "t" is one. I have not seen enough data to conclude that the knee is at 6 months, 9 months, 1 year, or even 1.5 years. The higher this value, the more time it will take before this component slows.

I am willing to agree with the consensus that the time-dependent loss is the largest loss component right now, but I still feel perhaps 30% of more of reported loss might be best-fit correlated with charge cycling, if it turns out that temperature amplifies cycling loss as well as shelf-life loss. If the cycling component is non-negligible now, it will gradually become a bigger fraction of the total loss and our total loss will not "level out" as much as many have hoped.

Those of us with Gid meters in more moderate but still warm climates are showing continued loss. I am hopeful that, by keeping the car out of the sun when parked, and cooling the garage at night, I will not experience a loss of a full capacity bar by October, when the warm weather ends.

Daytime 81-85 F
Night-time 65-65 F
Charge begins 4 am
Now limiting charge to 65-72 % range many nights.
Last charge to 100% June 5: 267 Gids (95%)

80% charges:
5-30: 225 Gids (-2.1 %)
6-9: 223 Gids
6-24: 219 Gids (down 12 Gids from Winter high) -4.3%

I believe it is unrealistic to assume I will lose less than another 12 Gids at 80% by October. The corresponding 100% loss will be proportionately higher, perhaps 12% loss, which will feel quite constraining.

Well, another one bites the dust.

Lost a capacity bar about 20 minutes ago.

2011 LEAF, purchased and delivered on 8/6/2011. Lost the capacity bar on 6/21/2012 (10 months and 15 days) at 10,216 miles.

Typical charging - almost always to 80% (including weekends) with 100% charges approximately once every 3-4 weeks. 4 Quick Charges.

I'm going to take it in to the dealer tomorrow. I know the answer I'm going to receive, but I just want to create the paper trail.

1. Azdre - Reported bar lost mid April to early May, 2012. 17K miles/14 months ownership. Phoenix
2. bturner - May 12, 2012. 13.6K/12 months. Phoenix
3. turbo2ltr - May 18, 2012. 13K/15 months. Phoenix
4. TickTock - May 20, 2012. 14K/12 months Phoenix
5. Volusiano - May 20, 2012. 16.5K/12 months. Phoenix
6. Mark13 - May 22, 2012. 15.7K/12 months. Phoenix
7. Leafkabob - May 26, 2012. 9.5K/12 months. Phoenix
8. Cyellen - June 7,2012. 10.2K/14 months. Phoenix
9. RickS - June 10, 2012. 11.3K/13 months. Phoenix
10. Pipcecil - June 17, 2012. 20.2K/12 months. Dallas, Texas
11. Phxsmiley - June 17, 2012. 13.7K/10 months. Phoenix
12. AZknauer - June 17, 2012. 9.2K/13.5 months. Phoenix
13. Myleaf - June 19, 2012. 13.3K/14 months. Phoenix
14. johndoe74 - June 5, 2012. 13.5K/ 9 months. Phoenix
15. Matt Ferris - June 20, 2012. 15K/ 12 months. Dallas, Texas (Reported on GreenAutoBlog)
16. shrink - June 21, 2012. 10.2K miles/10.5 months. Phoenix

Not reported by owner, but by others:
1. Opossum has reported of two cars in Phoenix that have lost 2 bars.
2. Leafkabob reported a street encounter with a Leaf owner who stated he lost a bar after about a year.
3. Skywagon approx. May, 2012. Phoenix

shrink said:

Well, another one bites the dust.

Lost a capacity bar about 20 minutes ago.

2011 LEAF, purchased and delivered on 8/6/2011. Lost the capacity bar on 6/21/2012 (10 months and 15 days) at 10,216 miles.

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Sorry to hear that. Just want to let you know that some of us in the cooler parts of the country fully support those of you in Phoenix and related areas that have been affected by this accelerated battery capacity loss. I don't think the "blame the victim" approach some are taking is going to go over well, and don't want to see this issue split the Leaf community.

It looks like about one per day is being reported on the forum here. I think we are at a total of 20 Leafs now.

cwerdna said:

1. Azdre - Reported bar lost mid April to early May, 2012. 17K miles/14 months ownership. Phoenix
2. bturner - May 12, 2012. 13.6K/12 months. Phoenix
3. turbo2ltr - May 18, 2012. 13K/15 months. Phoenix
4. TickTock - May 20, 2012. 14K/12 months Phoenix
5. Volusiano - May 20, 2012. 16.5K/12 months. Phoenix
6. Mark13 - May 22, 2012. 15.7K/12 months. Phoenix
7. Leafkabob - May 26, 2012. 9.5K/12 months. Phoenix
8. Cyellen - June 7,2012. 10.2K/14 months. Phoenix
9. RickS - June 10, 2012. 11.3K/13 months. Phoenix
10. Pipcecil - June 17, 2012. 20.2K/12 months. Dallas, Texas
11. Phxsmiley - June 17, 2012. 13.7K/10 months. Phoenix
12. AZknauer - June 17, 2012. 9.2K/13.5 months. Phoenix
13. Myleaf - June 19, 2012. 13.3K/14 months. Phoenix
14. johndoe74 - June 5, 2012. 13.5K/ 9 months. Phoenix
15. Matt Ferris - June 20, 2012. 15K/ 12 months. Dallas, Texas (Reported on GreenAutoBlog)
16. shrink - June 21, 2012. 10.2K miles/10.5 months. Phoenix

Not reported by owner, but by others:
1. Opossum has reported of two cars in Phoenix that have lost 2 bars.
2. Leafkabob reported a street encounter with a Leaf owner who stated he lost a bar after about a year.
3. Skywagon approx. May, 2012. Phoenix

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Isn't it interesting how the loss of a bar is clustering around the mid june timeframe ??

shrink said:

2011 LEAF, purchased and delivered on 8/6/2011. Lost the capacity bar on 6/21/2012 (10 months and 15 days) at 10,216 miles.

Typical charging - almost always to 80% (including weekends) with 100% charges approximately once every 3-4 weeks. 4 Quick Charges.

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I've had mine one week more and 2,000 miles more, charging pattern almost identical. Still holding good here in TN. It's 90 in the garage this evening. Wonder if Tennessee will start reporting later this year once the heat takes it's toll. The problem does seem to be restricted to the hotter states for now.

I see you have 7 temp bars, I've had 6 or less all year. Only saw 7 temp bars once last year after driving fast in heat and charging soon after.

JPWhite said:

I see you have 7 temp bars, I've had 6 or less all year. Only saw 7 temp bars once last year after driving fast in heat and charging soon after.

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I think that 7 temperature bars (= 98.2 degree F. or above) means that your Leaf has a fever. If the fever persists or goes higher, your Leaf is going to have some degree of brain (battery pack) damage. I have never seen 7 bars on my Leaf, it is usually at 5 bars, but spends significant time at 6 bars in the Valley during the summer; my pack appears to be in good shape (around 95-96% on a full charge by Gid-o-meter last I checked). I propose that time spent at 7 bars or above may be a good indication of who is going to have premature aging of the pack (assuming Leaf is not left at high SOC for significant periods of time). This fits well with the information on the Volt chemistry that 90 degrees is a lot worse for the pack (5 year life expectancy if) than 72 degrees (8 year life expectancy). My guess is that higher spikes are even worse, even if few and short-lived.

Stoaty said:

Sorry to hear that. Just want to let you know that some of us in the cooler parts of the country fully support those of you in Phoenix and related areas that have been affected by this accelerated battery capacity loss. I don't think the "blame the victim" approach some are taking is going to go over well, and don't want to see this issue split the Leaf community.

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Thanks, Stoaty. Much appreciated.

JPWhite said:

Wonder if Tennessee will start reporting later this year once the heat takes it's toll.

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Hope not, JP. It'll happen to all of us eventually, but I would hope in TN it will be much farther out than 10 months.

Stoaty said:

I think that 7 temperature bars (= 98.2 degree F. or above) means that your Leaf has a fever. If the fever persists or goes higher, your Leaf is going to have some degree of brain (battery pack) damage. I have never seen 7 bars on my Leaf, it is usually at 5 bars, but spends significant time at 6 bars in the Valley during the summer; my pack appears to be in good shape (around 95-96% on a full charge by Gid-o-meter last I checked). I propose that time spent at 7 bars or above may be a good indication of who is going to have premature aging of the pack (assuming Leaf is not left at high SOC for significant periods of time). This fits well with the information on the Volt chemistry that 90 degrees is a lot worse for the pack (5 year life expectancy if) than 72 degrees (8 year life expectancy). My guess is that higher spikes are even worse, even if few and short-lived.

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Yeah, there's been discussion on the regional Phoenix thread. Most of us are getting 6 temp bars in the AM and 7 in the afternoons/evenings. If I recall correctly, temps started entering the 100's in mid May or so. I do wish there was more guidance on this. If I'm remembering the manual correctly, as long as the temp bars are not too low and in the blue or too high and in the red, that is considered within the "normal" range for the battery.

Well, higher temps are obviously having an effect.

Sorry about that shrink, its becoming clearer that charging to 80% wont save you in Phoenix.

Maybe with the higher temperature, the higher voltage reaches a threshold that is equivalent to charging to 100%... really wish we knew if maintaining a lower than 80% SOC was worthwhile... I'm erring in that direction now, since I am enjoying somewhat frequent QC's!

Herm said:

Sorry about that shrink, its becoming clearer that charging to 80% wont save you in Phoenix.

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Herm said:

Sorry about that shrink, its becoming clearer that charging to 80% wont save you in Phoenix.

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Thanks, Herm, but thank you more for the Gozer reference and picture. My cat is actually named Gozer and your almost out of the blue reference was very witty and cracked me up! Loved it.

GaslessInSeattle said:

... really wish we knew if maintaining a lower than 80% SOC was worthwhile...

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I've wondered that since I got the car. Am I needlessly limiting my range ina range limited vehicle? Since Nissan went to the trouble of creating a feature and mentioning charge level for long life in the manual I'd comply where possible. In fact as I have gained experience in how far it will go 'per bar' I charge to 100% less often as my experience and confidence level increases regarding practical range.

Stoaty said:

This fits well with the information on the Volt chemistry that 90 degrees is a lot worse for the pack (5 year life expectancy if) than 72 degrees (8 year life expectancy).

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This implies that Volts will tend to have similar battery lives. OTOH, LEAFs will experience a wide range of battery life. In fact, I expect that many LEAFs will have much longer-lived batteries than the Volts because their batteries will live at lower temperatures. Time will tell.

I am not Volt specialist but what I know Volt allow battery temp to be from 18 to 90F and if not plugged or charged TMS will be off on hot day or cold day. Running TMS while driving won't be enough to keep battery at 71, same apply to low temp assuming that car is driven for half electric range each way.

EdmondLeaf said:

I am not Volt specialist but what I know Volt allow battery temp to be from 18 to 90F and if not plugged or charged TMS will be off on hot day or cold day.

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I'm certainly not an expert here, either. If 18F is really the lowest target for the Volt TMS, then I am wrong here. But I though it was 50F. If 50F and with a thermal time constant measured in hours, I would expect Volt batteries to live at a much higher average temperature than LEAF batteries in cold climates.

RegGuheert said:

EdmondLeaf said:

I am not Volt specialist but what I know Volt allow battery temp to be from 18 to 90F and if not plugged or charged TMS will be off on hot day or cold day.

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I'm certainly not an expert here, either. If 18F is really the lowest target for the Volt TMS, then I am wrong here. But I though it was 50F. If 50F and with a thermal time constant measured in hours, I would expect Volt batteries to live at a much higher average temperature than LEAF batteries in cold climates.

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Re: Volt, TMS, and battery temp
From this article:
http://www.caranddriver.com/reviews/2011-chevrolet-volt-full-test-road-test

... requires its own coolant circuit in order to heat or cool the 288 cells to keep them in the optimal temperature range (32° to 90°F).

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SAE article:

Temperature extremes can diminish a battery’s efficiency and rapidly accelerate battery aging, noted Frank Weber, Volt’s enthusiastic and laser-focused Global Chief Engineer who departed the program last year for Opel.

“For example, the delta between 70°F (21°C) and 90°F (32°C) can be critical to battery life,” he asserted. The battery is designed to work while plugged in, at temperatures from -13°F (-25°C) to +122°F (+50°C). The permitted temperature gradient within a battery cell, and from cell to cell, is 5 to 10 K.

A 50:50 glycol mixture is actively circulated through 144 metal “fins” between each of the Volt’s 288 cells. The fins are 1-mm-thick (0.04-in) stamped aluminum plates that conduct heat. The Volt’s pack has five thermal management circuits to handle the multiple subsystems. The system uses multiple electric coolant pumps (12- and 50-W) supplied by Buehler Motor of Germany. The pumps feature brushless dc motors and integrated electronics, and are designed to run extremely quietly, explained Robert Riedford, President of Buehler Motor Inc.

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And a very interesting post in the past few days from SH on gm-volt

This morning I drove rather aggressively, and so I was showing 2.4kWh used for my 10.1 mile commute and a battery temp of 82F (outside gauge said 83F) when I parked. When I got in the car after nine hours of high temps increasing to triple digits (car said 106F when I finally started it,) it showed a battery temp of 90F; I'm not positive if the TMS hit the battery - if so it didn't use much power (there's a 1-200 Wh discrepancy with some of the numbers that could be TMS activity,) and the 16 degree delta could be the result of thermal mass and insulation.

The remote start hit the fan hard pretty quickly - for the majority of it the remote start was drawing around 5 kW while it ran, with momentary drops to 2.8/3.0 and an instantaneous peak of 5.4 kW. I could also hear the radiator fan running.

It seemed to prioritize the cabin - the battery didn't change from 90 for the first few minutes - but by the end of the ten minutes the battery showed 84F, clearly showing the battery was being cooled effectively. From the changes to the "battery remaining" calculation off of the reported SoC in the DashDAQ, the remote start used ~650Wh - but when I started the car, is showed 3.2 kWh used (the discrepancy I mentioned; the SoC often has a slight mismatch to the overall use for some reason - it always starts showing 10.2-10.4, but it;ll show zero when the engine kicks on and the car will say 9.9 used.)

When I turned it on, the car was soon hitting the same 5kW in Park; by the end of my drive home even though the fan was at the same speed and the air blowing cold, the draw was down to around 2kW (colder recycled air means less work for the compressor causing the reduced draw?) and the battery average temp was down to 75F.

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scottf200 said:

Re: Volt, TMS, and battery temp
From this article:
http://www.caranddriver.com/reviews/2011-chevrolet-volt-full-test-road-test

... requires its own coolant circuit in order to heat or cool the 288 cells to keep them in the optimal temperature range (32° to 90°F).

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Thanks, Scott! Interesting stuff! 32F sounds like a decent lower target to me. I'll retract my comment based on that. Volt batteries should do fine in cold climates since they will also limit the high-temperature extremes in summertime.

Sorry to take this off-topic. Back to the regularly-scheduled thread...

There was also this article RE: the Volt:

http://www.hybridcars.com/news/gm-tweaks-2013-volt-increased-range-and-more-46843.html" onclick="window.open(this.href);return false;

While GM has milked an incremental gain in energy density, it also reports “tests have revealed less battery degradation,” not that there were known problems before.

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I'd say that's in stark contrast to the LEAF, especially in warm climates.

I thought a lot about Volt allowing 90F, sure owner have big effect what temp car will be maintained. I will keep it in temp close to 71 as much as possible. If you have TMS you have choice where you want to be concerning battery temp, but my results trying to keep Leaf battery in 71, not driven and not charged, are not very encouraging. I think I will be lucky if I will be able to maintain 85 without AC when heat dome get stacked here next week. I do not understand battery temp gauge. For hot areas, and I guess for all too, 71- 98F (bar 6) seems to be very important segment and will greatly help to maintain car at lower range if one know what temp really is. If one is at the top of the bar, as Stoaty mentioned that battery have a fever. If we will know that battery is approaching fever state, many will apply remedy, unfortunately range of the bar prevent that. I will be much happier if I know what battery temp really is so I will apply medicine as needed. I am very sad that Volt medicine was not included in Leaf

Stoaty said:

This fits well with the information on the Volt chemistry that 90 degrees is a lot worse for the pack (5 year life expectancy if) than 72 degrees (8 year life expectancy).

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Where do these Volt chemistry estimates come from? I recall someone writing at a GM-Volt.com forum that GM engineers at a Detroit event with Volt owners unofficially said Volt packs would likely last around 14-15 years in mild temperature areas and 10-13 in hot climates like the Southwest (when reasonable care is taken like parking in shade or leaving connected to an EVSE for TMS).