Capacity Loss on 2011-2012 LEAFs

[mkjayakumar]

I am not sure replacing a few cells is the right solution. That will give you a few more months of better range only to find yourself in the same state again..I

 

[Herm]

You guys might have a few bad modules (or one) bringing the whole pack down prematurely, Nissan might be becoming receptive to fixing these cases now that the brown stuff has hit the fan.. it cant be inexpensive to fix. You will never know unless they tell you a module is significantly lower than the rest.

 

[LEAFfan]

You guys might have a few bad modules (or one) bringing the whole pack down prematurely, Nissan might be becoming receptive to fixing these cases now that the brown stuff has hit the fan.. it cant be inexpensive to fix. You will never know unless they tell you a module is significantly lower than the rest.

It's very unlikely they have bad modules. In this kind of heat, it's the whole battery that degrades, not just a few cells or modules. When I was down about 10%, I thought that some cells went bad, but every one tested 'good' and I was given a copy of the whole report. At the time of the test, I was down to 2-3 fuel bars.

 

[Joeviocoe]

You guys might have a few bad modules (or one) bringing the whole pack down prematurely, Nissan might be becoming receptive to fixing these cases now that the brown stuff has hit the fan.. it cant be inexpensive to fix. You will never know unless they tell you a module is significantly lower than the rest.

It's very unlikely they have bad modules. In this kind of heat, it's the whole battery that degrades, not just a few cells or modules. When I was down about 10%, I thought that some cells went bad, but every one tested 'good' and I was given a copy of the whole report. At the time of the test, I was down to 2-3 fuel bars.

From what I've heard, there is a small fan inside the sealed pack that keeps the temperature consistent to avoid hot spots and single modules going bad. I suppose it could happen though. But I don't see it as likely. The problem is showing statistically to be heat soak degrading the calendar life. Which is something that would affect all modules equally within the pack.

 

[TonyWilliams]

From what I've heard, there is a small fan inside the sealed pack that keeps the temperature consistent to avoid hot spots...

Not true. There was in prototypes, but not production LEAFs.

 

[surfingslovak]

It's very unlikely they have bad modules. In this kind of heat, it's the whole battery that degrades, not just a few cells or modules. When I was down about 10%, I thought that some cells went bad, but every one tested 'good' and I was given a copy of the whole report. At the time of the test, I was down to 2-3 fuel bars.

As we have heard in one of the many interviews recently, Nissan can track the state and health of the battery pack through CarWings very granularly, supposedly down to the cell level. If any of the affected Leafs had a bad module or two, it's possible that a repair would have been attempted. Additionally, Randy indicated that a cell-pair voltage test was conducted on his car and revealed that the pack was Normal (TM).

He also showed me the voltage output of all 96 cells of the battery were in specification. I tried to explain to him that the output voltage of a battery means nothing if it can only sustain that for a limited amout of time. He just told me this shows there is not obvious issues with the battery and therefore the car is working "normally".

 

[Joeviocoe]

From what I've heard, there is a small fan inside the sealed pack that keeps the temperature consistent to avoid hot spots...

Not true. There was in prototypes, but not production LEAFs.

Thanks. Didn't know that.

 

[DaveEV]

It's very unlikely they have bad modules. In this kind of heat, it's the whole battery that degrades, not just a few cells or modules. When I was down about 10%, I thought that some cells went bad, but every one tested 'good' and I was given a copy of the whole report. At the time of the test, I was down to 2-3 fuel bars.

While I agree that it's generally the entire pack that degrades, I think you really need to go below LBW to get a better picture of weak cells.

In fact, if I'm understanding Nissan's test procedures - you are more likely to trigger a case for cell replacement with the lowest SOC possible since that's most likely to generate the highest differences in cell voltage.

 

[Herm]

While I agree that it's generally the entire pack that degrades, I think you really need to go below LBW to get a better picture of weak cells.
In fact, if I'm understanding Nissan's test procedures - you are more likely to trigger a case for cell replacement with the lowest SOC possible since that's most likely to generate the highest differences in cell voltage.

Probably so but not to Nissan's interest to test there. Voltages will start to vary wildly below the knee anyways.

 

[DaveinOlyWA]

It's very unlikely they have bad modules. In this kind of heat, it's the whole battery that degrades, not just a few cells or modules. When I was down about 10%, I thought that some cells went bad, but every one tested 'good' and I was given a copy of the whole report. At the time of the test, I was down to 2-3 fuel bars.

While I agree that it's generally the entire pack that degrades, I think you really need to go below LBW to get a better picture of weak cells.

In fact, if I'm understanding Nissan's test procedures - you are more likely to trigger a case for cell replacement with the lowest SOC possible since that's most likely to generate the highest differences in cell voltage.

actually when you get that low, you will be unable to detect any issues due to a pretty wide variance that can still be considered "ok"

now with lead acid (granted much different but still a battery) i saw weak cells very early in my ZENN. problem with "pack mentality" is batteries work the same way. they find the weakest cell and exploit it and early. in most cases a weak cell can be detected easily at SOC of 60-80% under even moderate loads.

what happens is weaker cells will have greater voltage drop. essentially the knee appears to move to a fairly high voltage level (this is reason why degraded cells still charge to 393 volts) which means the knee voltage effect will happen to the weak cell long before the rest of the pack gets there.

if you look at cells as not singular units but a group of entities that hold a charge. the voltage on each entity is equal to the cell voltage. now suppose you have a bad cell in with a bunch of good ones. the bad cell has 100 units of charge, the good cells have 200 units of charge. the "knee" happens when you are at 25 units of charge (numbers for illustration only) so it would make sense that when the pack calls on each cell for a total of 75 units of charge the bad cell will start to reveal itself correct? wrong.

as the pack calls for power, say one unit, each cell (when balanced) gives up a single charge unit and under load, the voltage drop occurs. when pack is full, the cells have a lot of resilience to this drop. but the weaker cell since its started only half charged to begin with, its voltage drop will be greater

 

[JRP3]

what happens is weaker cells will have greater voltage drop. essentially the knee appears to move to a fairly high voltage level (this is reason why degraded cells still charge to 393 volts)

Weak cells still charge to the same voltage because they are top balanced by the BMS, which means they are unbalanced at the bottom. Weak cells will show increased voltage drop near the end of discharge since they have less capacity. Reading the voltage of each cell, or cell pair, during discharge will point out the weak cells.

 

[RegGuheert]

now with lead acid (granted much different but still a battery) i saw weak cells very early in my ZENN. problem with "pack mentality" is batteries work the same way.

Dave, did the ZENN have a sophisticated cell balancing scheme with shunts across each cell as is employed in the LEAF?

 

[DaveinOlyWA]

now with lead acid (granted much different but still a battery) i saw weak cells very early in my ZENN. problem with "pack mentality" is batteries work the same way.

Dave, did the ZENN have a sophisticated cell balancing scheme with shunts across each cell as is employed in the LEAF?

yep!! that is after i installed one. and it was shunts across each battery. it did balance 24/7 but was simply too weak to head of degradation. the amount of power transfered from battery to battery was pretty small.

in a vain effort to extend my battery pack life, i would charge for an hour (only took about 3) then let it sit and it would take up to 90 minutes to balance which obviously was a bit inconvenient.

 

[leiko49]

2nd bar loss this morning, first bar reported about 2 months ago (in Wiki). 10,100 miles! Given my loss of battery capacity, I might just drop my yearly Leaf mileage (due to range loss, and lack of opportunity to charge on the fly) from 10K a year to the Nissan normed average of 7,500. At least I'll know I am now normal.

 

[TonyWilliams]

2nd bar loss this morning, first bar reported about 2 months ago (in Wiki). 10,100 miles! Given my loss of battery capacity, I might just drop my yearly Leaf mileage (due to range loss, and lack of opportunity to charge on the fly) from 10K a year to the Nissan normed average of 7,500. At least I'll know I am now normal.

Fresh off the presses:

Use this 75% chart for a battery that has 10 of 12 capacity bar segments.

 

[leiko49]

2nd bar loss this morning, first bar reported about 2 months ago (in Wiki). 10,100 miles! Given my loss of battery capacity, I might just drop my yearly Leaf mileage (due to range loss, and lack of opportunity to charge on the fly) from 10K a year to the Nissan normed average of 7,500. At least I'll know I am now normal.

Fresh off the presses:

Use this 75% chart for a battery that has 10 of 12 capacity bar segments.

Your truly magic graph will not grant me the magick I seek, to return to the day when the car was anew, and a 107 number graced my fully charged GOM (Nissan pseudo magick), minus the 2% a year promise. I was naive back then, I know that now. But still, I dream.

 

[cwerdna]

2: The only people that win in class action lawsuits (or any for that matter) are the lawyers. IANAL, so I will not participate in any class action.

I've gotten close to 1000 dollars from class-action lawsuits. $25 from the CD/record Company cartel case, $85 from the paypal case, and 800 from the Equinox MLM class-action case.

I'm getting $4500 (in an unrelated suit) as a named plaintiff, as are the other 7 named plaintiffs, after two years of back and forth in court. The class members who aren't named are getting $10 each. The lawyers are getting $3.5 million. I wouldn't peruse legal action like this again. The only plus side of it for me is that the company we sued is going to have to change the way they do business, which was very important to me personally.

FWIW, I wanted to amend my statements about the best class action settlement I've gotten. Previously it was for http://www.girardgibbs.com/Prius.asp" onclick="window.open(this.href);return false;, where I received a check for the cost of 2 HID bulbs (~$110 total, IIRC) bought from Amazon, even though I was a bit past the time and mileage provided by the settlement's warranty extension when one of my HID bulbs started failing.

Today, I was shocked and pleasantly surprised to receive a settlement check of over $3000 (!) for something totally unrelated. (If one's curious, Google for rosemary cohorst bre settlement. And no, I am not Rosemary Cohorst and did no work other than filling out the paperwork. But, I did rent apartments and look for apartments w/the companies involved.) It had to do w/unauthorized (not informing all parties about) recording of phone calls. I'm glad I filled out the paperwork!

That said, I've gotten settlement notices where the award was so tiny or useless, it wouldn't be even worth my effort to fill out the papers, find the documentation, makes copies, etc. There was one guy on Tivocommunity who got a $0.07 settlement check as a result of some Ebay class action suit. Numerous other chimed in of awards of <$0.30. :roll:

 

[leafkabob]

Nissan buys back more cars: http://www.plugincars.com/nissan-moves-resolve-leaf-range-loss-claims-124827.html

 

[azdre]

It's very unlikely they have bad modules. In this kind of heat, it's the whole battery that degrades, not just a few cells or modules. When I was down about 10%, I thought that some cells went bad, but every one tested 'good' and I was given a copy of the whole report. At the time of the test, I was down to 2-3 fuel bars.

While I agree that it's generally the entire pack that degrades, I think you really need to go below LBW to get a better picture of weak cells.

In fact, if I'm understanding Nissan's test procedures - you are more likely to trigger a case for cell replacement with the lowest SOC possible since that's most likely to generate the highest differences in cell voltage.

We had Nissan do a cell test at full SOC and at VLBW. Variances were in tolerance both times.

 

[DaveinOlyWA]

It's very unlikely they have bad modules. In this kind of heat, it's the whole battery that degrades, not just a few cells or modules. When I was down about 10%, I thought that some cells went bad, but every one tested 'good' and I was given a copy of the whole report. At the time of the test, I was down to 2-3 fuel bars.

While I agree that it's generally the entire pack that degrades, I think you really need to go below LBW to get a better picture of weak cells.

In fact, if I'm understanding Nissan's test procedures - you are more likely to trigger a case for cell replacement with the lowest SOC possible since that's most likely to generate the highest differences in cell voltage.

We had Nissan do a cell test at full SOC and at VLBW. Variances were in tolerance both times.

which is the expected result in well manufactured packs. Nissan did a great job in balancing cells. (too much concentration on that and not enough of temperature effects i guess :? )