Capacity Loss on 2011-2012 LEAFs

[edatoakrun]

Which is why I think that many with gid meters may be mistaken in their conviction that gid meters can be depended on to determine total battery capacity, much less actual battery "degradation".

IMO, It's sort of pathetic to hear of so many LEAF drivers leaving their cars at home, and driving their ICEVs on hot days, or even worse, selling or trading in their LEAFs, just because they have seen a dropping gid count.

I am not leaving my Leaf at home on hot days due to dropping Gid count. I am leaving it at home because hot weather has been shown to greatly accelerate capacity loss, and Nissan has said "this is normal". Remember that of the 7 Leafs tested at Casa Grande, the best one had still lost 14% of capacity. If we ever hear something different from Nissan officially, I may change my behavior. However, right now I am just protecting my investment with a few weeks of driving my ICE when temperatures are above 95 degrees.

Remember, the Casa Grande LEAFs were selected because they were the cars showing the greatest capacity bar loss, in the hottest climate where LEAFs are sold, worldwide.

And, yes, the very incomplete reports we have are of capacity losses of 14% to 15%, (IIRC) from those LEAFs, many of which had histories of high miles driven, and, quite possibly, other extreme battery uses, which would themselves be expected to lead to faster capacity loss.

I seriously doubt that paying for gas and maintenance to drive an ICEV on days above 95 degrees is cost-effective, and can really be justified as "protecting (your) investment", on the basis of the information on battery capacity loss now available.

 

[surfingslovak]

I'm very interested to see the Gid count for each car at 100% charge and at lbw. It would be great to circle a QCer until all the cars reach lbw or vlbw. Then we could measure average capacity loss over time and miles in AZ.

Great idea, please be sure to record pack voltage both at the beginning and at the end of the test. It's the only value that supposedly comes directly from the battery and it's a source of truth. I've been very busy the last few days, but I'm ready and willing to mail you my Gid meter if it helped conduct the test.

 

[TickTock]

I up for the range test. 9/15 looks open right now.

 

[TonyWilliams]

I seriously doubt that paying for gas and maintenance to drive an ICEV on days above 95 degrees is cost-effective, and can really be justified as "protecting (your) investment", on the basis of the information on battery capacity loss now available.

Honestly, your thinking is perfectly inline with every denier of climate change: not enough proof, but if you are wrong, then what? If it turns out the awesome Nissan battery design was in fact the best for Phoenix, and it's just simple (and cheap) instrument and software issues, nothing was lost for those owners who choose to drive their ICE in hot weather (except some gas).

But, if there is indeed an issue, they made a smart, logical choice that may aid the long(er) life of their poorly designed car.

 

[TonyWilliams]

I'm very interested to see the Gid count for each car at 100% charge and at lbw. It would be great to circle a QCer until all the cars reach lbw or vlbw. Then we could measure average capacity loss over time and miles in AZ.

Great idea, please be sure to record pack voltage both at the beginning and at the end of the test. It's the only value that supposedly comes directly from the battery and it's a source of truth. I've been very busy the last few days, but I'm ready and willing to mail you my Gid meter if it helped conduct the test.

Awesome. I'd like to take this conversation to the thread I started:

Please post replies to this thread

 

[TonyWilliams]

I up for the range test. 9/15 looks open right now.

Woo Hoo!!! I know it will be a good test then :mrgreen:

Let's move the details and planning to to the other thread.

Please post replies to this thread

 

[Stoaty]

Remember, the Casa Grande LEAFs were selected because they were the cars showing the greatest capacity bar loss, in the hottest climate where LEAFs are sold, worldwide.

Yes, at the time there weren't many Leafs with more severe capacity loss, but we now have about 30 with 2 bar loss or more--and that is just the ones we happen to know about. It may be that there will be hundreds in 6-12 months more.

I seriously doubt that paying for gas and maintenance to drive an ICEV on days above 95 degrees is cost-effective, and can really be justified as "protecting (your) investment", on the basis of the information on battery capacity loss now available.

In that case, feel free to drive your Leaf no matter the temperature.

 

[DaveEV]

I seriously doubt that paying for gas and maintenance to drive an ICEV on days above 95 degrees is cost-effective, and can really be justified as "protecting (your) investment", on the basis of the information on battery capacity loss now available.

In that case, feel free to drive your Leaf no matter the temperature.

Let's look at this from a logical perspective with some back-of-the-envelope calculations.

Assumptions:
1. Capacity degradation due to temperature follows Arrhenious equation.
2. Not driving the car for a day reduces the pack temperature by 10C for 12 hours (battery might stay at 82F instead of 100F).
3. Too-hot temperatures last for 3 months of the year.

Baseline is that by not driving the car for 90 days, you maintain 100% capacity.
By driving your car 5 days/week to work, you subject the car to 60 days * 12 hours of 2x degradation. This is like adding 2 months of extra wear - so instead of 3 months of aging, you add 2 months of aging to the car.

But during that time, you've lost 3 months of use of the car.

So - in my very rough back-of-the-envelope calculations - unless you can keep the battery at least 15-20C cooler than it would be otherwise - by avoiding using the car on hot days you are actually getting less use out of the battery than you would otherwise.

This doesn't take into account any degradation rates due to SOC differences - it's nearly certain that most cars in storage will be sitting at 80% instead of something lower it's sitting in the heat.

 

[edatoakrun]

Remember, the Casa Grande LEAFs were selected because they were the cars showing the greatest capacity bar loss, in the hottest climate where LEAFs are sold, worldwide.

Yes, at the time there weren't many Leafs with more severe capacity loss, but we now have about 30 with 2 bar loss or more--and that is just the ones we happen to know about. It may be that there will be hundreds in 6-12 months more.

I seriously doubt that paying for gas and maintenance to drive an ICEV on days above 95 degrees is cost-effective, and can really be justified as "protecting (your) investment", on the basis of the information on battery capacity loss now available.

In that case, feel free to drive your Leaf no matter the temperature.

I more or less do.

But I try avoid driving, when it's really hot (which I consider over 105 or so) whenever possible, for my own benefit, more than my battery's.

And if it helps relieve your or anyone else's anxiety, my LEAF, which is older, has more miles (~12,400), and has probably had many more charge cycles, much more high kW use and high kW charging by regen (due to mountainous terrain) and also has (perhaps) experienced higher peak and average battery temperatures than yours while driving, still has no detectable loss of range, and no loss of capacity bars, either.

However, the one thing I have almost never done, unlike most LEAF owners, is park in a closed garage at night, so I never have prevented my battery pack from taking advantage of the very significant overnight ambient temperature declines, to cool off my battery pack.

 

[Stoaty]

Assumptions:
1. Capacity degradation due to temperature follows Arrhenious equation.
2. Not driving the car for a day reduces the pack temperature by 10C for 12 hours (battery might stay at 82F instead of 100F).
3. Too-hot temperatures last for 3 months of the year.

Well, my Leaf will be at 70 degrees F if left at home, 100 degrees F if driven on a hot day, which means a difference of 16.7 degrees C. So far, I have not driven the Leaf for about 4 weeks this summer following my rule. Since I work 4 days a week this means about 16 days I didn't drive the Leaf. I can drive it the other 3 days of the week since I live near the coast where it is much cooler. So my Leaf doesn't fit your assumptions at all.

This doesn't take into account any degradation rates due to SOC differences - it's nearly certain that most cars in storage will be sitting at 80% instead of something lower it's sitting in the heat.

At work the Leaf is at about 60% SOC during the day; when left at home it is about 40% SOC. Again, your assumptions don't fit my Leaf, so the rest of the analysis won't be valid.

 

[DaveinOlyWA]

guess its a bit early to expect significant cooling in Phoenix yet but what is anyone predicting one would get back when it does cool down? 5%? 10%? (i am guessing around 7-8%) but what good is that going to do for someone who is 25% down?

now; one possible scenario; 5-10% temporary loss added to say 5-10% " heat adjustment" by Car to psyche driver into doing what?? who knows? so maybe when all is said and done, the worst case scenarios are in the 10% range?

either way, a blanket statement that the gauges are wrong without a followup statement means nothing. where is the "we should have a software fix available by the end of the month?"

he is stalling. pure and simple. waiting on something. guessing a ready supply of replacement batteries. guessing he will try to replace the worst of the worst quietly to prevent a run on replacement requests from people who are only seeing expected degradation (what ever that is)

please post here if anyone gets a NDA request

 

[mwalsh]

guess its a bit early to expect significant cooling in Phoenix yet but what is anyone predicting one would get back when it does cool down? 5%? 10%?
<snip>
guessing he will try to replace the worst of the worst quietly to prevent a run on replacement requests from people who are only seeing expected degradation (what ever that is)

I don't know. I do hope it has significant restorative effect, but a part of me has doubts. One thing I'm certain of...I've never wished for winter to arrive this hard my entire life.

Oh, and I do think we should be supplied with some kind of explanation as to what the average person should reasonably expect in terms of yearly degradation.

 

[ALLWATZ]

Not sure if anyone has read this yet (http://wendang.baidu.com/view/f461ea27a5e9856a5612605a.htmlbut" onclick="window.open(this.href);return false(you might have to use your google translate, although I didn't have to), just found it online and has some interesting concepts about the battery. It's an obscure article/thesis by the developers of the battery in our Leafs from 2006. Most of it is technical but I thought 2 points were very interesting and revealing (you guys may find more).
The first is under section 2.1, third paragraph, last sentence, talking about predicting battery degradation. This would indicate that they have no idea, when including all real world factors (including high climate heat), how it would react.
Second, is the fourth paragraph, first sentence, where they state that they would need "large volumes of battery data". Anyone else feel like we are mice in a lab? Why else would they need to have the battery checks and what better way to get it than sell a bunch of cars to people and require this (oh, but we'll throw it in for free!)?
Not sure if there is a smoking gun here for anyone but one last thing. At the bottom of the article are the names and e-mail addresses of the designers of the battery. I believe that Mr. Takeshi Miyamoto, Nissan’s EV Energy Development Department project leader, is the one who actually holds the patent on it. Up till now, all of us have been dealing with Nissan-USA and been stonewalled. It might be enlightening to contact someone, politely, from corporate in Japan (assuming Nissan-USA is actually informing them of our situation) to see their response. At the very least, Mr. Takeshi Miyamoto being a scientist/engineer, should be interested in all of the data everyone here has collected as that is what he asked for in this very article/thesis.

P.S. it looks like anyone should be able to contact Nissan Corp. in Japan as I have seen other execs listed with the same address, @mail.nissan.co.jp, the trick would be to figure out the name designation in front of the @.

 

[JRP3]

Your link is messed up. Proper link http://wendang.baidu.com/view/f461ea27a5e9856a5612605a.html" onclick="window.open(this.href);return false;

 

[TonyWilliams]

I do hope it has significant restorative effect, but a part of me has doubts. One thing I'm certain of...I've never wished for winter to arrive this hard my entire life.

Oh, and I do think we should be supplied with some kind of explanation as to what the average person should reasonably expect in terms of yearly degradation.

Winter might be cruel, if there is no "restorative" effect (which I absolutely think is optimism in the highest degree :ugeek:

I guarantee winter will decrease the available power, restorative effect or not.

 

[ALLWATZ]

Your link is messed up. Proper link http://wendang.baidu.com/view/f461ea27a5e9856a5612605a.html" onclick="window.open(this.href);return false;

Oops. Sorry, it worked for me. Tony, this might be someone you would want to contact after you've done the tests in AZ?.

 

[KJD]

According to Tony's range charge LBW will happen at 49 GID's and that is 17.4% SOC.

Tony's chart is based on a 12-bar car. I don't recall anyone checking when LBW, VLBW and turtle show up on a 11 bar or less car.

OK correct me if I am wrong but I seem to remember reading somewhere in these 340 pages that LBW happens at 49 GID's regardless of weather the car has 12 bars, 11 bars or 10 bars.

Is this correct?

 

[mwalsh]

I guarantee winter will decrease the available power, restorative effect or not.

I guess that depends on when in winter we're talking about and how mild (or not) said winter might be in SoCal this year. I'm thinking that any restorative effect might start showing in late October or early November, and we won't be having really cold days (for us at least) until well into December. It also bears remembering that we've only had 2-3 light frost days each winter for the last couple of years, so we definitely appear to be trending more mild.

 

[DaveinOlyWA]

According to Tony's range charge LBW will happen at 49 GID's and that is 17.4% SOC.

Tony's chart is based on a 12-bar car. I don't recall anyone checking when LBW, VLBW and turtle show up on a 11 bar or less car.

OK correct me if I am wrong but I seem to remember reading somewhere in these 340 pages that LBW happens at 49 GID's regardless of weather the car has 12 bars, 11 bars or 10 bars.

Is this correct?

ya, pretty much. i have seen LBW at 50 and 51 a few times but usually 49

 

[surfingslovak]

OK correct me if I am wrong but I seem to remember reading somewhere in these 340 pages that LBW happens at 49 GID's regardless of weather the car has 12 bars, 11 bars or 10 bars.

Is this correct?

ya, pretty much. i have seen LBW at 50 and 51 a few times but usually 49

This is apparently by design. AFAIK Nissan begins to manage available power at 4 kWh remaining, which translates to the low battery warning at the transition between 49 and 50 Gids (50 x 80Wh = 4kWh). The regimen supposedly tightens at 2 kWh, and the very low battery warning appears at the transition between 24 and 25 Gids (25 x 80Wh = 2kWh).

Due to this design philosophy, we don't expect any of these thresholds to change. They represent fixed energy reserves, not SOC percentages. For what it's worth, my car has lost about 10% capacity, yet the Gid count at both the LBW and VLBW has not changed, and remained very predictable.

Lithium ion battery empty warning light

When your battery has 4kWh remaining, your empty warning light will come on and go into a power management mode. A notification on your screen will indicate where to find all charging stations within range.

Power limitation mode

In the event that your battery becomes critically low (2kWh), power limitation mode will automatically minimize your energy consumption and reduce your speed to help you get to a charging dock.

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