Capacity Loss on 2011-2012 LEAFs

spooka said:

leafkabob said:

because the only problem with charging to 100% is the amount of heat that is generated between 80% and 100%. The ABC Nissan leaf tech that was helping with this was nodding his head in agreement at this remark.

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I was told this also by a Blink/Ecotality tech that I met a the 101/17 QC station at Bell Ford about a month ago. He said this was especially an issue with QCing. I am thinking that the best way to combat the heat issue when charging beyond 80% is to L-1 charge to keep the heat as low as possible.

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On standard L2 - there is no appreciable heat generated from 80-100%. QC - yes. L2 - you're not going to see a difference between it an L1 the charge rates are so low. Will have to ask Ingineer to do some data logging of pack temperature during a L2 charge...

Edit: Asked and Phil was quick to answer (Thanks Phil!):

Ingineer said:

The 2 rates are so close that the difference isn't really observable. Keep in mind, while the L1 is a lower rate, it's doing it for longer, which seems to tie with the L2 rates because they finish a lot faster.

Now if it was really cold/hot out, these numbers may change, but here in NorCal, I don't notice any difference. Even when I charge at 6.7kW!

The battery has a certain resistance, and it's got a LOT of thermal mass with little effect from the outside air, so it's pretty linear up to the point where the chemistry non-linearity starts to affect it. (Which probably doesn't start until around 1/2C rates)

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vegastar said:

Making a cell voltage difference at 383.53V total pack voltage is not effective. 383.53V/96 = 3.995, very close to the maximum, so the minimum cell voltage is an outlier and the maximum cell voltage is the norm. 24mV difference from the average cell voltage is equivalent to 381.22 total pack voltage if all the cells were like the weakest one. This 2.31V difference is around 1 kW.h of energy, so around 5% total pack capacity. I think the cell voltage difference must be done in 100% charge to check for imbalances, and around the knee of the voltage (3.71V) to check for damaged cells.

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There's a reason why the service manual says to check for cell voltage differences with 2 SOC bars or less. I'd argue that it should be done at LBW or lower, preferably at VLBW or lower. 100% is not effective because the LBC should be actively balancing the cells.

The Leaf segment on EVTV from October 5:

drees said:

There's a reason why the service manual says to check for cell voltage differences with 2 SOC bars or less. I'd argue that it should be done at LBW or lower, preferably at VLBW or lower. 100% is not effective because the LBC should be actively balancing the cells.

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Correct, all the 100% test shows is that the BMS is top balancing the cells, it does not show if a cell has lost capacity, which will only show up on discharge. The proper test would be to do a 100% charge, check all cell voltages to see if they are being balanced, then fully discharge the pack, checking cell voltage sag under load, and cell voltage at the end of discharge. Cells with lost capacity would hit low voltage before the rest, limiting your range, cells sagging excessively under load before a low SOC is reached would show excessive internal resistance and indicate replacement.

The problem with sitting at 100% SOC for extended periods is the electrolyte is subjected to the higher voltage potential for a a longer period, which speeds electrolyte solvent breakdown.

L1 or L2 charging should make no difference since near the end of charge the charge current is cut back in both cases.

I'm afraid some people at Nissan don't really know what the hell they are doing or saying!

leafkabob said:

Here are the numbers from the Min/Max Voltage test:
HV Battery - Maximum Cell Voltage - 3997 mV
HV Battery - Minimum Cell Voltage - 3971 mV
HV Battery - Total Battery Voltage - 383.53 V
That's my report.

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You need to go back and ask them to perform the test properly. The very first step in the CVLI is to check if the minimum cell voltage is 3712 or less (April 2011 SM page EVB-268). You should hit this just below VLBW. The delta between the cells is less at higher charge levels thanks to top-side balancing so this result is meaningless. Based on this and the other comments from your dialog (as well as some from my own interview), it is clear very few people inside Nissan really understand the car (and probably none of them in the US).

vegastar said:

leafkabob said:

Here are the numbers from the Min/Max Voltage test:
HV Battery - Maximum Cell Voltage - 3997 mV
HV Battery - Minimum Cell Voltage - 3971 mV
HV Battery - Total Battery Voltage - 383.53 V

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Great report!

Making a cell voltage difference at 383.53V total pack voltage is not effective. 383.53V/96 = 3.995, very close to the maximum, so the minimum cell voltage is an outlier and the maximum cell voltage is the norm. 24mV difference from the average cell voltage is equivalent to 381.22 total pack voltage if all the cells were like the weakest one. This 2.31V difference is around 1 kW.h of energy, so around 5% total pack capacity. I think the cell voltage difference must be done in 100% charge to check for imbalances, and around the knee of the voltage (3.71V) to check for damaged cells.

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+1 (and NOW I see vegastar already covered this)

TonyWilliams said:

I posted a response addressing that, amongst other sundry items.

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Thanks Tony, that was an irritating article..

TickTock said:

leafkabob said:

Here are the numbers from the Min/Max Voltage test:
HV Battery - Maximum Cell Voltage - 3997 mV
HV Battery - Minimum Cell Voltage - 3971 mV
HV Battery - Total Battery Voltage - 383.53 V
That's my report.

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You need to go back and ask them to perform the test properly. The very first step in the CVLI is to check if the minimum cell voltage is 3712 or less (April 2011 SM page EVB-268). You should hit this just below VLBW. The delta between the cells is less at higher charge levels thanks to top-side balancing so this result is meaningless. Based on this and the other comments from your dialog (as well as some from my own interview), it is clear very few people inside Nissan really understand the car (and probably none of them in the US).

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I appreciate all of the comments on the validity of the test. As a non-techie, my conclusion is that Nissan probably knows very well how to properly conduct the test, but has decided that for purposes of "resolving cases on an individual basis" their current testing method is up to snuff. In other words, my guess is they have already decided what they will or will not do for me, and the tests are simply designed to rule out any obvious defects with the battery.

The host clearly takes exception to the claim that Chelsea is an "EV Expert..."

surfingslovak said:

The Leaf segment on EVTV from October 5

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TomT said:

The host clearly takes exception to the claim that Chelsea is an "EV Expert..."

surfingslovak said:

The Leaf segment on EVTV from October 5

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I think they have a unique angle, since they are predominantly catering to the conversion crowd. In Jack's mind, many of us would not qualify either. We just drive the damn things. That said, I agree with his opinion that the role of early adopters will be crucial, and Nissan would be well advised to engage them properly. I'm a bit dismayed to see that with the exception of their PR and CS vendors, they seem to have dropped off the forum in recent weeks. Perhaps it's just a much needed break after the hot summer?

Perhaps they've lost some capacity and are waiting for cooler weather to see if it comes back! :lol:

surfingslovak said:

TomT said:

The host clearly takes exception to the claim that Chelsea is an "EV Expert..."

surfingslovak said:

The Leaf segment on EVTV from October 5

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I think they have a unique angle, since they are predominantly catering to the conversion crowd. In Jack's mind, many of us would not qualify either. We just drive the damn things. That said, I agree with his opinion that the role of early adopters will be crucial, and Nissan would be well advised to engage them properly. I'm a bit dismayed to see that with the exception of their PR and CS vendors, they seem to have dropped off the forum in recent weeks. Perhaps it's just a much needed break after the hot summer?

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There is where I think Nissan is blowing it... the first wave of customers can generate a ton of sales. We are the canary in the coal mine to friends and family. Personally, I am sure I can generate at least ten~ unit sales as a trusted recommender. Nissan Leaf could very well turn into a Harvard Business Case Study!

mdh said:

Personally, I am sure I can generate at least ten~ unit sales as a trusted recommender. Nissan Leaf could very well turn into a Harvard Business Case Study!

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I have sold more than this for Nissan. I'm still selling; I just make it clear that leasing is the only logical way to drive the LEAF.

For the mega-high mileage crowd, a lease won't work and a new battery will likely be too expensive to beat the price of the Just-Drive-The-Prius(TM) crowd. If they understand it might cost MORE, then I still recommend the car, but would certainly steer them to the Tesla, Rav4, etc.

High mileage AND high ambient heat is CLEARLY a loser of a combination for the LEAF.

drees said:

On standard L2 - there is no appreciable heat generated from 80-100%. QC - yes. L2

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I thought that on QC, that charge rate between 80-100% slows down considerably to avoid the heat issue, no? I assume that the 80-100% charge rate on QC is not any worse than that of L2 because of this slow down, am I wrong to assume?

Volusiano said:

drees said:

On standard L2 - there is no appreciable heat generated from 80-100%. QC - yes. L2

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I thought that on QC, that charge rate between 80-100% shows down considerably to avoid the heat issue, no? I assume that the 80-100% charge rate on QC is not any worse than that of L2 because of this slow down, am I wrong to assume?

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It does both; slows down because of heat, and generates A LOT OF HEAT !!!

TomT said:

Perhaps they've lost some capacity and are waiting for cooler weather to see if it comes back! :lol:

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Gentlemen, plug in your Gid meters! :lol:

mdh said:

There is where I think Nissan is blowing it... the first wave of customers can generate a ton of sales. We are the canary in the coal mine to friends and family. Personally, I am sure I can generate at least ten~ unit sales as a trusted recommender. Nissan Leaf could very well turn into a Harvard Business Case Study!

Click to expand...

TonyWilliams said:

I have sold more than this for Nissan. I'm still selling; I just make it clear that leasing is the only logical way to drive the LEAF.

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Indeed, Nissan's stance was pretty enigmatic, even before we suffered through the bout of battery angst this summer. Although they gave clear positive signals recently, I have hard time recognizing a cohesive approach in this regard. I don't know, perhaps I'm the only one. The advisory board might fill some of this void, but I would think that they could do better on the sales side, and engage owners more broadly.

I really liked all the talks and presentations GM gave about the Voltec drivetrain. I don't know if they had a referral program for the Volt, but it would seem like a no-brainer for the Leaf.

On a related note, cwerdna mentioned how Toyota would invite a group of active participants from Priuschat to a private event. If such invites were not limited to one or two people on Nissan's speed dial, it would create a lot of goodwill, and help improve communication. That would be my two cents, anyway.

TonyWilliams said:

mdh said:

Personally, I am sure I can generate at least ten~ unit sales as a trusted recommender. Nissan Leaf could very well turn into a Harvard Business Case Study!

Click to expand...

I have sold more than this for Nissan. I'm still selling; I just make it clear that leasing is the only logical way to drive the LEAF.

For the mega-high mileage crowd, a lease won't work and a new battery will likely be too expensive to beat the price of the Just-Drive-The-Prius(TM) crowd. If they understand it might cost MORE, then I still recommend the car, but would certainly steer them to the Tesla, Rav4, etc.

High mileage AND high ambient heat is CLEARLY a loser of a combination for the LEAF.

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The Sunnyvale Nissan Dealer NEVER recommended leasing to me or any of my friends. It will be interesting to see how Nissan treats/views the "installed" based of owners with time.

surfingslovak said:

In Jack's mind, many of us would not qualify either.

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In Jack's mind he is the only expert even when he's wrong.

leafkabob said:

I appreciate all of the comments on the validity of the test. As a non-techie, my conclusion is that Nissan probably knows very well how to properly conduct the test, but has decided that for purposes of "resolving cases on an individual basis" their current testing method is up to snuff. In other words, my guess is they have already decided what they will or will not do for me, and the tests are simply designed to rule out any obvious defects with the battery.

Click to expand...

But that's the point, their tests simply do not achieve that goal, all they do is show that the BMS is effectively top balancing the cells. If you have two cells, one at half the capacity of the other, but during charge you make sure they both finish at the same voltage, that does not show how out of balance they really are. That would show up only during discharge.

JRP3 said:

leafkabob said:

I appreciate all of the comments on the validity of the test. As a non-techie, my conclusion is that Nissan probably knows very well how to properly conduct the test, but has decided that for purposes of "resolving cases on an individual basis" their current testing method is up to snuff. In other words, my guess is they have already decided what they will or will not do for me, and the tests are simply designed to rule out any obvious defects with the battery.

Click to expand...

But that's the point, their tests simply do not achieve that goal, all they do is show that the BMS is effectively top balancing the cells. If you have two cells, one at half the capacity of the other, but during charge you make sure they both finish at the same voltage, that does not show how out of balance they really are. That would show up only during discharge.

Click to expand...

Perhaps I should have said their test is simply designed to show me that they generated some data.

surfingslovak said:

TomT said:

Perhaps they've lost some capacity and are waiting for cooler weather to see if it comes back! :lol:

Click to expand...

Gentlemen, plug in your Gid meters! :lol:

mdh said:

There is where I think Nissan is blowing it... the first wave of customers can generate a ton of sales. We are the canary in the coal mine to friends and family. Personally, I am sure I can generate at least ten~ unit sales as a trusted recommender. Nissan Leaf could very well turn into a Harvard Business Case Study!

Click to expand...

TonyWilliams said:

I have sold more than this for Nissan. I'm still selling; I just make it clear that leasing is the only logical way to drive the LEAF.

Click to expand...

Indeed, Nissan's stance was pretty enigmatic, even before we suffered through the bout of battery angst this summer. Although they gave clear positive signals recently, I have hard time recognizing a cohesive approach in this regard. I don't know, perhaps I'm the only one. The advisory board might fill some of this void, but I would think that they could do better on the sales side, and engage owners more broadly.

Click to expand...

I thought they were giving positive signals, too, until I dealt with them last week and realized they had simply decided to double down on denial and their position now is to stonewall, stonewall, stonewall, in a bid to buy them more time and hope that we get tired and stop badgering. They quieted the loudest people--the ones who were going on TV--so maybe that's their definition of a customer-relations success.

I've PM'd Chelsea about my unfortunate and unproductive exchange with Nissan, but haven't heard back from her yet.