Capacity Loss on 2011-2012 LEAFs

[planet4ever]

I hope somebody will correct me, but I thought the capacity bars were 15%, then 7.5%, then 6.25%, etc. i cant find the actual Nissan chart.

The table currently in the Wiki shows 6.25% for every bar after the first. I believe that came from the first edition of the Nissan LEAF Service Manual. I have a private image file dated 2011-01-11 showing the same thing that I downloaded from the forum. The Wiki references page MWI-23, which has no table at all in the second (April 2011) edition. Instead that page has a pictorial "glass half full" explanation of why you can have 12 charge bars when you don't have 12 capacity bars. Whether the table was removed by accidental omission, because it was inaccurate, or because Nissan didn't want us to know, is a matter for conjecture.

Ray

 

[RegGuheert]

Scott: I lost my fourth bar today at 28,190 miles.

Added to Wiki.

Scott: It gets turned in September 15th.

At least Scott was leasing and has some recourse. To date Nissan has offered no recourse for owners like opossum and azdre.

 

[JRP3]

I know the Lithium batteries are superior on paper, but the track record of the EV-95 NiMH battery in the real world is incredible. I would trade the Lithium pack for a NiMH pack in a New York second (if they could be built---thanks Chevron :evil: ) even with the lower energy density and hence higher mass and physical size. Ten years from now it will be interesting to see how many (if any) LEAF's will have their orginal packs and orginal range.

Certainly not any in AZ However, I'd expect to see Honda Fit packs last that long, since they use SCIB Li titanate cells. The mistake is treating all lithium cells as a single chemistry when they are not. So if you are looking to swap out your lithium pack then choose a better lithium chemistry.

 

[scottf200]

Scott: I lost my fourth bar today at 28,190 miles.

Added to Wiki.

Via wiki for mileage/time reference

1 bar_: Apr 07, 2012 Scott Yarosh Avondale, AZ 20000 miles 10 months
2 bars: Jun 07, 2012 Scott Yarosh Phoenix, AZ  23800 miles 12 months
3 bars: Jul 07, 2012 Scott Yarosh Phoenix, AZ  25870 miles 13 months
4 bars: Aug 31, 2012 Scott Yarosh Phoenix, AZ  28190 miles 14 months

 

[Herm]

I wonder how much Nissan will get for selling Scotts Leaf with 4 bars missing.

 

[RegGuheert]

Via wiki for mileage/time reference

1 bar_: Apr 07, 2012 Scott Yarosh Avondale, AZ 20000 miles 10 months
2 bars: Jun 07, 2012 Scott Yarosh Phoenix, AZ  23800 miles 12 months
3 bars: Jul 07, 2012 Scott Yarosh Phoenix, AZ  25870 miles 13 months
4 bars: Aug 31, 2012 Scott Yarosh Phoenix, AZ  28190 miles 14 months

Yeah, I was looking at that. Not a lot of leveling off going on.

It's going to be hard to get much data beyond the loss of the fourth bar since I expect most will dump the car by about that time, just as Scott is doing.

 

[Stoaty]

It's going to be hard to get much data beyond the loss of the fourth bar since I expect most will dump the car by about that time, just as Scott is doing.

This is certainly a black eye for Nissan. Even a leased Leaf in one of their first markets can't make it more than 14 months. Nissan tests the car, returns it to the owner, and then does... nothing. :twisted:

 

[edatoakrun]

Scott: I lost my fourth bar today at 28,190 miles.

Added to Wiki.

Via wiki for mileage/time reference

1 bar_: Apr 07, 2012 Scott Yarosh Avondale, AZ 20000 miles 10 months
2 bars: Jun 07, 2012 Scott Yarosh Phoenix, AZ  23800 miles 12 months
3 bars: Jul 07, 2012 Scott Yarosh Phoenix, AZ  25870 miles 13 months
4 bars: Aug 31, 2012 Scott Yarosh Phoenix, AZ  28190 miles 14 months

Too bad that we haven't heard the overnight SOC (80% or 100%), recharging habits, and ambient temperature (garaged at night-how hot?) on this car (IIRC).

The fact that he was still putting ~2,000 miles a month, until very recently, on a car with what many consider to be a battery degraded to less than 70% of capacity, with (possibly) less than 70% of new driving range, would tend to indicate a large proportion of 100% charges, and very many mid-day recharges or QC sessions, in Phoenix Summer temperatures.

I wonder if his battery pack has spent much time at 8 or more dash temperature bars?

Herm

I wonder how much Nissan will get for selling Scotts Leaf with 4 bars missing.

I'd say about $22k, give or take a $k.

With a new battery pack.

I think Nissan will probably want to take this pack apart to see what cooked it.

 

[TonyWilliams]

Just to be clear, while the threshold for 4 lost capacity bars is 33.75% total battery loss, it could be as much as 39.99%.

Therefore, I suggest that the actual losses be described as such; one bar lost is 15%-21.24%, etc.

1 bar - 15.00% to 21.24%: Apr 07, 2012, 20000 miles, 10 months of service since new
2 bars - 21.25% to 27.24%: Jun 07, 2012, 23800 miles, 12 months (3800 miles/2 months)
3 bars - 27.50% to 33.74%: July 07, 2012, 25870 miles, 13 months (2070 miles/1 month)
4 bars - 33.75% to 29.99%: Aug 31, 2012, 28190 miles 14 months (2320 miles /1.7 months)
5 bars - 40.00% is the next threshold displayed on the LEAF's dash instrument of 12 total bars.

 

[brettcgb]

I'm sorry to hear about your bar loss, Brett.

Am I correct in saying that this is only the second report of a 2012 LEAF losing a bar?

Finally, Brett, can you please update your LEAF VIN number in the User Control Panel? 5143 is too low for a 2012 LEAF. I'm thinking you must have entered that at some point in the past when the forum only permitted 4 digits. Perhaps it is 15143? TIA!

Done.
I don't know how many other 2012s have lost a bar.

As an early adopter (and everyone here is) I expected some capacity loss. I didn't expect it so soon, but I'm also not very surprised. It hasn't impacted my daily travel, but trips to the far side of town now need to be planned a little better (each way was always at the limit of my range). I'm not angry or upset, but I am very interested.

 

[Herm]

Herm
I wonder how much Nissan will get for selling Scotts Leaf with 4 bars missing.

I'd say about $22k, give or take a $k.
With a new battery pack.
I think Nissan will probably want to take this pack apart to see what cooked it.

They know what cooked it, they have known for a long time.

 

[mksE55]

Herm
I wonder how much Nissan will get for selling Scotts Leaf with 4 bars missing.

I'd say about $22k, give or take a $k.
With a new battery pack.
I think Nissan will probably want to take this pack apart to see what cooked it.

They know what cooked it, they have known for a long time.

Heat you silly Rabbit.

 

[JeremyW]

Via wiki for mileage/time reference

1 bar_: Apr 07, 2012 Scott Yarosh Avondale, AZ 20000 miles 10 months
2 bars: Jun 07, 2012 Scott Yarosh Phoenix, AZ  23800 miles 12 months
3 bars: Jul 07, 2012 Scott Yarosh Phoenix, AZ  25870 miles 13 months
4 bars: Aug 31, 2012 Scott Yarosh Phoenix, AZ  28190 miles 14 months

What this tells me is that there is no leveling off. Capacity loss accelerates after loosing the first bar.

The level period is for the first year or two when the pack is new. Then range plummets.

Jeremy

 

[mksE55]

Via wiki for mileage/time reference

1 bar_: Apr 07, 2012 Scott Yarosh Avondale, AZ 20000 miles 10 months
2 bars: Jun 07, 2012 Scott Yarosh Phoenix, AZ  23800 miles 12 months
3 bars: Jul 07, 2012 Scott Yarosh Phoenix, AZ  25870 miles 13 months
4 bars: Aug 31, 2012 Scott Yarosh Phoenix, AZ  28190 miles 14 months

What this tells me is that there is no leveling off. Capacity loss accelerates after loosing the first bar.

The level period is for the first year or two when the pack is new. Then range plummets.

Jeremy

seems logical, the packs that are left will cycle more and you will need to do deeper cycles to keep your range. This worsens as bars drop off. and a Viscous cycle continues. They should have made the design with about 23-24Kw, and software to cont to maintain 21Kw battery, as the initial battery was broke in and you lost the first 10%, the software would give you slow access to the rest of the battery, and then it would slow down your loss and you would really start with 21Kw battery for the life of the car instead of 15% loss within the first year or less. why didnt they break the batteries in with charge cycles, they stil break motors in before the put then in Cars. Ok enough rambling for now. And these people are the Professionals/scientist.

 

[mwalsh]

What this tells me is that there is no leveling off. Capacity loss accelerates after loosing the first bar.

The level period is for the first year or two when the pack is new. Then range plummets.

Jeremy

But that's contrary to what we understand about lithium packs. Traditionally you would see the worst degradation during the early life of the pack. I've asked this elsewhere and never got an answer, but will somebody with more experience in these matters explain to me why we're seeing this now with these packs?

 

[brettcgb]

What this tells me is that there is no leveling off. Capacity loss accelerates after loosing the first bar.

The level period is for the first year or two when the pack is new. Then range plummets.

Jeremy

But that's contrary to what we understand about lithium packs. Traditionally you would see the worst degradation during the early life of the pack. I've asked this elsewhere and never got an answer, but will somebody with more experience in these matters explain to me why we're seeing this now with these packs?

Simple enough. Deep discharges are hard on batteries, the deeper, the harder, and the battery wears out faster.

If the car is driven the same distance each day, and is losing capacity, its going deeper into discharge each day. Rinse and repeat.

 

[ztanos]

Via wiki for mileage/time reference

1 bar_: Apr 07, 2012 Scott Yarosh Avondale, AZ 20000 miles 10 months
2 bars: Jun 07, 2012 Scott Yarosh Phoenix, AZ  23800 miles 12 months
3 bars: Jul 07, 2012 Scott Yarosh Phoenix, AZ  25870 miles 13 months
4 bars: Aug 31, 2012 Scott Yarosh Phoenix, AZ  28190 miles 14 months

He went 20,000 miles in 10 months. Don't we have people in moderate climates losing bars with this amount of miles? Maybe this is a combination of miles and heat?

 

[Nekota]

I don't mean to upset or add stress to those that have lost capacity bars and I'm not looking forward to when I start seeing bars in my LEAF disappear. But for every problem there have to be causes and effects and seeking to blame something is part of our means of dealing with loss (http://en.wikipedia.org/wiki/K%C3%BCbler-Ross_model" onclick="window.open(this.href);return false.

So considering heat as a key process input variable (KPIV) I'm wondering if high power rates from 'fast' acceleration can create local hot spots in the battery cell structure and lead to more rapid capacity loss. One way to gauge this would be the use of ECO vs D where in ECO the current demand is more controlled than in D. I apologize if there is discussion on this but my search key words did not find one but this was close (http://www.mynissanleaf.com/viewtopic.php?f=27&t=8925" onclick="window.open(this.href);return false. Another possible gauge would be accelerated tire wear unless you drive in a curvy area (eg mountain roads).

As for hot spots a planar cell structure (don't know why it's called prismatic) I would expect a hot spot would show increased resistance and shift the current away from the area as a negative feedback or self compensation. Are there any thoughts on what positive feedback factors could generate heat and lead to a thermal runaway hotspot? Again this is purely a conjecture.

 

[JRP3]

There does seem to be a cascade effect where constant heat soaking, and charging while hot, degrades capacity, which leads to a higher and higher percentage of available capacity being used to travel the same distance, which exacerbates the capacity loss. There might be some slow down of capacity loss if one could also proportionally reduce daily miles driven, but that's not practical. I'm not sure what's going on inside the cells but it could be as basic as the electrolyte breaking down in the heat. It's possible that use of a different electrolyte would provide better heat resistance.

 

[RegGuheert]

I'm not sure what's going on inside the cells but it could be as basic as the electrolyte breaking down in the heat. It's possible that use of a different electrolyte would provide better heat resistance.

IMO, you have just named precisely the cause of the problem with LEAF battery capacity losses in very hot climates followed by the solution to the problem. Unfortunately, it seems that Li-ion battery capacity loss due to the breakdown of the electrolyte does not taper off over time, but rather it accelerates. Please have a look at the shape of the curve with the light blue triangles in Figure 5b on page 301 of that document. (Don't worry, it is not 301 pages long!)

Another article in MIT's Technology Review discusses the problem with the lithium hexafluorophosphate in today's lithium-ion batteries and one solution provided by a company called Leyden Energy:

Leyden's battery replaces lithium hexafluorophosphate, one of the components of a lithium-ion battery, with imide salt. Unlike lithium hexafluorophosphate, it does not react with water inside the battery cell, a reaction that significantly degrades the cycle life of a battery. Lithium hexafluorophosphate also starts to decompose at room temperature and loses its effectiveness more significantly when the temperature hits 55 °C. Imide salt doesn't start to decompose at higher temperatures.

However, like most technological improvements, there are severe drawbacks to replacing the popular electrolyte with imide salt, as described later in the same article:

But imide salt can cause trouble by corroding the aluminum current collector that is typically found in a battery cell. Graphite makes a good substitute because it is immune to this assault. "The key advance for Leyden is not the electrolyte. Their magic is, they are not using aluminum as the current collector," says Venkat Srinivasan, a scientist at the Lawrence Berkeley National Laboratory who has seen the company's technology. "This change allowed them to change the electrolyte."

Unfortunately, I am willing to bet that a graphite current collector has a much higher electrical resistance than one made out of aluminum.

I will say if I could get a LEAF with 50% more capacity (what Leyden Energy is promising) but only 50% of the power of the current model, but with greatly reduced calendar capacity losses, I would call that a big improvement. I certainly hope that Nissan is looking into precisely what JRP3 has prescribed. I like that approach much better than the addition of a TMS since with the right chemistry I feel it will prove to be the most reliable solution available for BEVs.