Capacity Loss on 2011-2012 LEAFs

[azdre]

Add me to the 11 bar list. I should have reported it sooner on this thread.

I live in the Phoenix area, and I saw my Leaf drop to 11 bars around June 15th at ~8500 miles and ownership time of 14.5 months.

FYI - I am now keeping the original post up-to-date with the list of 'losers'. DarkDave has been added.

 

[SanDust]

Take away the cycling and you still have calendar losses, so I would say heat has its own loss mechanism. Granted, I haven't seen many studies of calendar losses without cycling (of course there are a few cycles to measure the battery), but the one I have seen on chemistry similar to the Tesla shows calendar losses ACCELERATING once you pass a 15% drop in capacity.

Unfortunately, that is the regime the LEAF batteries in Phoenix are being operated in: calendar losses dominating over cycling losses. Does the LEAF have the same shape for its calendar losses? I don't know, but in absence of evidence to the contrary, I will suspect that it does. None of the anecdotal evidence posted on this forum to date leads me to believe otherwise.

Just to be fair to Tesla, the study you cite most certainly did not look at batteries being used in the Model S. The study was published in 2004 and the new Panasonic cells were only released in 2012. The cells used in the Leaf also would not have been available. I'm not completely clear what cells they looked at but they didn't look at what is being used in EVs now.

But the bigger problem is that you've misinterpreted the study. All the study finds is that overcharging the battery or storing a battery with a full SOC for an extended period of time results in a loss of battery capacity, especially at high temperatures. I'm assuming that neither of these things is happening to the Leaf batteries in Phoenix.

Keep in mind that what your'e calling calendar losses and cycling losses are the same thing. Basically you have the free Li ions in the electrolyte forming a layer on the anode. This is made clear by your study when it says: "The term ‘side reaction’ indicates the parasitic reactions between the electrolyte and reversible lithium, which forms complex organic products that are electrochemically inactive. Side reactions occur on both electrodes but predominantly on the surface of the negative electrode."

In this regard, there are things a manufacturer can do to prevent this from occurring. For example, they can apply a layer to the anode that resists the formation of a further layer. So just because a study says X about Y battery doesn't mean you can apply the same findings to Z battery. The general trends will be there but you can't apply the numbers exactly.

 

[DaveEV]

Update: full charge overnight went to 265 Gid (94.3%) and took 21.7 kWh from the wall.

Thanks for the data, definitely interesting and useful.

One thing I've wondered for a while is whether or not there's any other proxies for estimating capacity loss without a GID reading.

For example, surfingslovak's range table includes L1 charging time - his chart indicates that the car should estimate 21-22 hours to 100% once you hit LBW, but I know my car was at least an hour short last time I got there.

But going down to LBW or lower is not always convenient - after all, who wants to drive around needlessly wasting energy.

So whenever I need more than 80% charge, I hit the timer-override to charge to 100% about 2 hours before I leave and record the length of time and amount of energy my Blink records before it stops charging. I typically do this about once a month, here's the data I have for the last 6 months (how long I've been recording this):

Jan 2012: 1:28 4.959 kWh
Mar 2012: 1:25 4.667 kWh
Apr 2012: 1:14 ? kWh (Blink crashed, didn't record energy)
May 2012: 1:14 4.379 kWh
Jun 2012 1:13 4.247 kWh
Jul 2012 1:07 3.959 kWh

There's a clear trend here and it certainly looks like I'm down on capacity even though not showing of the impending signs yet. For sure, some of this could simply be caused by the pack being out of balance since I don't let the car sit at 100% for any longer than I need to. Regardless, this is very easy data for Blink owners to collect, even if they normally charge to 100%. Lots of LEAF owners have Blinks out there - would be very interesting to see what someone who's down to 11 bars records as well as anyone else.

 

[Herm]

For sure, some of this could simply be caused by the pack being out of balance since I don't let the car sit at 100% for any longer than I need to.

That is very interesting data.. I do think that too many people here worry about balancing and getting back that last 1%* but perhaps you should do it at least once every 6 months. If only for this kind of test. I would like to know how the BMS remaps the 80% point as the battery capacity fades.

*.. that they really never are going to use.

 

[Volusiano]

Add me to the 11 bar list. I should have reported it sooner on this thread.

I live in the Phoenix area, and I saw my Leaf drop to 11 bars around June 15th at ~8500 miles and ownership time of 14.5 months.

FYI - I am now keeping the original post up-to-date with the list of 'losers'. DarkDave has been added.

It would be nice to see the updated list posted up each time there's a new addition. Can you post it up here?

 

[RegGuheert]

Just to be fair to Tesla, the study you cite most certainly did not look at batteries being used in the Model S. The study was published in 2004 and the new Panasonic cells were only released in 2012.

I neither stated nor implied that these are the cells used in the Tesla. Obviously they are not, since the study was done with pouch cells. I merely stated that they were a "similar" chemistry.

The cells used in the Leaf also would not have been available.

Agreed. This study was done on cells using a different chemistry than the LEAF cells. The cells used in the Nissan LEAF are purported to be MORE sensitive to high temperatures than the chemistry used in this study.

I'm not completely clear what cells they looked at but they didn't look at what is being used in EVs now.

Let's hope not! This study is eight years old!

But the bigger problem is that you've misinterpreted the study.

Have I? I don't think so. My interpretation of the study is that it shows capacity loss ACCELERATING in pouch Li-ion cells after passing about 15% degradation. It clearly shows that.

All the study finds is that overcharging the battery or storing a battery with a full SOC for an extended period of time results in a loss of battery capacity, especially at high temperatures.

Sorry, that is not "all" the study shows. Note that the light blue curve in figure 5(b) represents cells stored at 4.0 Volts per cell open circuit at 35C. Note that the rate of capacity degradation of the cell gets faster as the cell degrades further. Please note that 4.0 Volts per cell is below the 100% voltage for the LEAF and probably is close to the 80% point in the LEAF.

I'm assuming that neither of these things is happening to the Leaf batteries in Phoenix.

While no LEAF is sitting at a constant 35C, many, many are sitting around at 80% charge (or higher) and their temperature approaches that level sometimes during the summertime. In Phoenix, the LEAF batteries will spend nearly ALL of their time between the 5C and the 35 C curves given. It is too bad they stopped the 5C testing after just 7 months.

In this regard, there are things a manufacturer can do to prevent this from occurring. For example, they can apply a layer to the anode that resists the formation of a further layer. So just because a study says X about Y battery doesn't mean you can apply the same findings to Z battery. The general trends will be there but you can't apply the numbers exactly.

No one said anything about exact numbers. My ENTIRE point in posting a link to this study was to show the trend of accelerating calendar capacity losses in Li-ion batteries.

Again, most studies show capacity loss under a cycling regime and those tend to slow down as cycling increases. But this study does not cycle the battery and the losses accelerate over time. You can claim the losses are the same, but I seriously doubt that is the case. Cycling a battery is quite a different condition than allowing it to sit charged.

 

[bturner]

I'm already on the one bar lost list.... Please update my status to "2nd Bar Lost - 7/7/2012"

Thanks,
bturner

 

[EdmondLeaf]

bturner sorry to hear that. Wonder if this going to slow any time soon, but not really optimistic here.

 

[Pipcecil]

I think Nissan was right when they publicly said the capacity loss was not linear. But, I think we all assumed it was non-linear and would decelerate. Instead the Nissan PR people ment was it would accelerate. See? They never lied, they said it was non-linear. A very cruel joke.

 

[EdmondLeaf]

http://www.youtube.com/watch?feature=player_embedded&v=DShtvd5jJHQ#!
1:05
I trust what Mark Perry said, 70-80% capacity left after 10 years. He is the Leaf guy

 

[TomT]

And I also believe in the tooth fairy... :lol:

I guess he needed to qualify that with "depending on where you live..."

http://www.youtube.com/watch?feature=player_embedded&v=DShtvd5jJHQ#!
1:05 I trust what Mark Perry said, 70-80% capacity left after 10 years. He is the Leaf guy

 

[EdmondLeaf]

And I also believe in the tooth fairy... :lol:

I guess he needed to qualify that with "depending on where you live..."

http://www.youtube.com/watch?feature=player_embedded&v=DShtvd5jJHQ#!
1:05 I trust what Mark Perry said, 70-80% capacity left after 10 years. He is the Leaf guy

"depending on where you live..." - latitude works great for me (Smyrna - OKC), I am very careful driver so I aim 80% after 10 years

 

[TangoKilo]

And I also believe in the tooth fairy... :lol:

I guess he needed to qualify that with "depending on where you live..."

http://www.youtube.com/watch?feature=player_embedded&v=DShtvd5jJHQ#!
1:05 I trust what Mark Perry said, 70-80% capacity left after 10 years. He is the Leaf guy

"depending on where you live..." - latitude works great for me (Smyrna - OKC), I am very careful driver so I aim 80% after 10 years

The battery is going to degrade over time no matter what you do. Just drive the car and enjoy your 73 miles... Besides, isn't everybody gonna trade in their LEAF and buy a new EV in 5 years anyway? I am...

 

[vrwl]

Add me to the 11 bar list. I should have reported it sooner on this thread.

I live in the Phoenix area, and I saw my Leaf drop to 11 bars around June 15th at ~8500 miles and ownership time of 14.5 months.

FYI - I am now keeping the original post up-to-date with the list of 'losers'. DarkDave has been added.

I added him to the Wiki

 

[smkettner]

... Besides, isn't everybody gonna trade in their LEAF and buy a new EV in 5 years anyway? I am...

No, I was thinking in 10 years I could buy a direct swap battery to give 150 mile range for about $3,000. And only if needed

 

[ztanos]

I'm going to assume that bturner is an arizona leaf.

 

[vrwl]

I'm going to assume that bturner is an arizona leaf.

Yep, here's where he/she reports their bar loss and info: http://www.mynissanleaf.com/viewtopic.php?p=197125#p197125" onclick="window.open(this.href);return false;

 

[surfingslovak]

I'm going to assume that bturner is an arizona leaf.

Yep, here's where he/she reports their bar loss and info: http://www.mynissanleaf.com/viewtopic.php?p=197125#p197125" onclick="window.open(this.href);return false;

He is in turbo2ltr's old spreadsheet as well:

 

[SanDust]

Again, most studies show capacity loss under a cycling regime and those tend to slow down as cycling increases. But this study does not cycle the battery and the losses accelerate over time. You can claim the losses are the same, but I seriously doubt that is the case. Cycling a battery is quite a different condition than allowing it to sit charged.

The point you're missing is that what you're calling "calendar losses" only occur when you don't cycle the battery. They only occur if you overcharge the battery and let it sit for many months or if you overcharge the battery and then keep overcharging the battery for months on end. At 35C. This is more an "either/or" situation rather than an "and" situation since you can't be cycling the batteries and not discharging them.

The question becomes: How are the Leaf batteries in Phoenix are being used? Are Leaf drivers charging their cars to 110% and then leaving them in their hot garage over the spring, summer and fall? Or are they using the cars every day and then charging them to 80% or 100% at night? If it's the former then your study offers some insights. If the latter then your study has nothing to offer. What you're calling "cycling losses" is really what happens when the Leaf owners use their Leafs as you'd expect them to.

As for causes of the capacity losses being the same, I quoted your study as describing exactly what these were. That you "seriously doubt" that the side reactions are the same ones that occur with cycling suggests you don't understand the chemistry. Why do you think cycling results in reduced capacity?

Just as an addition, note that a TMS on the Leaf would not affect the capacity losses under the test conditions of your study since it would not come into play.

 

[dgpcolorado]

Besides, isn't everybody gonna trade in their LEAF and buy a new EV in 5 years anyway? I am...

I wonder what the trade-in value of a five year old LEAF would be with two, three or four capacity bars missing in a market flooded with off-lease cars? Not very high would be my guess. My plan was to keep the LEAF and replace the battery pack as needed, assuming that Nissan was still in the business of making them.

No, I was thinking in 10 years I could buy a direct swap battery to give 150 mile range for about $3,000. And only if needed

While I would like for this to be true I wonder whether an advanced tech battery, and the specialized BMS to properly manage it, will ever be made for retrofitting a LEAF, even at a much higher price. Perhaps some sort of aftermarket upgrade will become available. But I think $3000 is a pipe dream.

I fervently hope that you are right and I am wrong.