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Marktm
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Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Tue Jul 23, 2019 5:37 am

Yes, now the decisions about how to make that happen quicker vrs extending battery life - within the confines of acceptable usage and care. I believe the "defective" is 10 years. However, a replacement "Lizard" start date might be in question??
2012 Leaf SL; 43,000 miles. Battery replaced November 1st, 2016.

Lothsahn
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Leaf Number: 007797

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Tue Jul 23, 2019 8:14 am

Marktm wrote:Depleted battery totally today with mix of highway, suburban, sitting with drive on. The final SOC was 2.4% with 4 GIDS. Full power was 80,000 watts right up until turtle. When turtle kicked in, the max was around 7000 watts (LeafSpy battery bar readings). At present L1 charging (for the next 12 hours of so!).

The battery values at shutdown:
I am going to re-iterate that it looks like you might have a couple slightly weak cells, but nothing I would call defective. This test really shows the car is running fairly well and the BMS is balancing out the differences. My 7-bar battery had significantly worse values than this, although it was a canary pack and heavily degraded.

The first LeafSpy you linked showed an average cell voltage of 3.45V, whereas the new graph shows a voltage of 3.1V. While this sounds like a huge difference, it's actually very small for the 24 kWh cells. See the SECOND discharge curve on this page: (the top discharge curve is the new 40 kWh cells):
https://pushevs.com/2018/01/29/2018-nis ... eal-specs/

The second curve shows the voltage falloff occurs at around 3.6V (use the top light blue line, as you were presumably not driving while getting the LeafSpy screenshot, which means you should be using the 1/3C line). If you look at this graph, you can see the difference between 3.45V and 3.1V is less than 1 Ah. Each cell holds 30 Ah, so a 1Ah difference is very small.

We know that the central battery cells in the Leaf pack heat up faster and stay hot longer, so they will wear out faster. This is amplified in hot environments, like yours. It is normal as the pack ages to have the center cells get slightly weaker than the outside ones and show small differences like this.

Honestly, I don't think you have a defect.
Marktm wrote:Yes, now the decisions about how to make that happen quicker vrs extending battery life - within the confines of acceptable usage and care. I believe the "defective" is 10 years. However, a replacement "Lizard" start date might be in question??
Your car looks fine to me. I would not try to stress it to bring out the "defect", as I don't think you have one. You're likely to just wear out your battery more quickly.

Are you getting the range you would expect out of this pack for your driving conditions? Are there any other symptoms, or is the only concern that the car is showing voltage differences and turtled 2-3% sooner than it should?
2011 Silver SV, purchased 2018, lives in Missouri (previously in CA)
LeafSpy Pro + BAFX Products OBDII dongle
Battery swap 2019/04/24 (87% SOH, 12 bar)

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Marktm
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Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Wed Jul 24, 2019 6:41 am

Losthan;

I appreciate your factual, technical insights. I helps us that are not so familiar with Li cell characteristics (used lead/acid most of my life!), to understand the significant voltage/amperage parameters that can be used to analyse cell performance/aging/failure. I don't believe I have a range issue, nor a power issue. Yes, my main concern is degradation that seems to be quite rapid by any realistic expectations of a modern EV - especially when compared to (let's say) a Tesla.
2012 Leaf SL; 43,000 miles. Battery replaced November 1st, 2016.

SageBrush
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Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Wed Jul 24, 2019 7:47 am

Lothsahn wrote:
The first LeafSpy you linked showed an average cell voltage of 3.45V, whereas the new graph shows a voltage of 3.1V. While this sounds like a huge difference, it's actually very small for the 24 kWh cells. See the SECOND discharge curve on this page: (the top discharge curve is the new 40 kWh cells):
https://pushevs.com/2018/01/29/2018-nis ... eal-specs/

The second curve shows the voltage falloff occurs at around 3.6V (use the top light blue line, as you were presumably not driving while getting the LeafSpy screenshot, which means you should be using the 1/3C line). If you look at this graph, you can see the difference between 3.45V and 3.1V is less than 1 Ah. Each cell holds 30 Ah, so a 1Ah difference is very small.
This weak cell test *should* be performed dynamically, while the car is putting out maximum power. That is where the weak cells will matter, because they will cause the car to limit power or go into turtle despite a SoC that is otherwise high enough to not trigger those conditions.

We have been told in multiple threads that Nissan will not perform, or will ignore cvli results unless a specific DTC is logged. It is tempting to guess that DTC occurs when the system hobbles power output, but that would occur only if the power demand exceeds the system allowance.

Put another way, I suspect that sustained maximum power is the way to expose weak cells and log the needed DTC.
What is sustained ? I'm not sure. 30 -60 seconds sounds reasonable to me since it could be seen in mountain driving.
If I hard Mark's LEAF I would stress test it every 6 months or so, and a week before the warranty lapses.

@lorenfb, do you have an opinion or advice ?
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

Lothsahn
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Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Wed Jul 24, 2019 12:02 pm

SageBrush wrote: This weak cell test *should* be performed dynamically, while the car is putting out maximum power. That is where the weak cells will matter, because they will cause the car to limit power or go into turtle despite a SoC that is otherwise high enough to not trigger those conditions.

We have been told in multiple threads that Nissan will not perform, or will ignore cvli results unless a specific DTC is logged. It is tempting to guess that DTC occurs when the system hobbles power output, but that would occur only if the power demand exceeds the system allowance.

Put another way, I suspect that sustained maximum power is the way to expose weak cells and log the needed DTC.
What is sustained ? I'm not sure. 30 -60 seconds sounds reasonable to me since it could be seen in mountain driving.
I get that the test should be performed at maximum load, but we're talking about the state of the cells and the LeafSpy that was pulled. In that graph, it shows that the weak cells are at most 2-3% lower capacity than the rest (excluding effects from cell balancing). This is not a significant difference and it doesn't indicate a cell defect. Encouraging the owner to try to "stress out" the pack to get those cells to fail quickly likely won't work--these cells were slightly weaker, but only slightly. Furthermore, those cells were not showing low voltage again in the next LeafSpy screenshot.

This is very different than, say, Dala, who had two cells that both self-discharged at a rapid rate AND had significantly less capacity than the rest. His car was going to turtle at high SOC's. That is clearly the case of broken cells.

Given how people with actual bad cells (not just slightly weak) have had trouble getting a DTC to trigger, I highly doubt a very small capacity difference will trigger a DTC, and attempts to get it to do so will likely just degrade the battery faster.
SageBrush wrote: If I hard Mark's LEAF I would stress test it every 6 months or so, and a week before the warranty lapses.
I would not. Turtling a battery is hard on it, as it gets the charge level quite low. Unless he starts to see evidence of an actual cell failure, you're not likely to trigger a DTC and you are stressing out the battery pack.
2011 Silver SV, purchased 2018, lives in Missouri (previously in CA)
LeafSpy Pro + BAFX Products OBDII dongle
Battery swap 2019/04/24 (87% SOH, 12 bar)

SageBrush
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Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Wed Jul 24, 2019 1:27 pm

No intent to accelerate degradation of the weak cells, and I do not recommend bring the battery SoC to normal Turtle (what is that -- 3.1 cell voltage or so ?)

I would stress the battery at somewhere between LBW and VLBW. It that leads to a DTC due to the weak cells the battery is defective.
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

GerryAZ
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Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Wed Jul 24, 2019 7:14 pm

Marktm's "weak cells" are not weak enough to be of concern at this time. For example, I had 363 mV difference last night on my way home. I also see VLBW come in with pack voltage above 360 volts (indicates a lot of energy is left in stronger cells). My experience is that results of CVLI tests are quite variable. LEAF Spy Pro performs the CLVI test whenever the average cell pair voltage is low enough to meet the guidelines in the service manual and the car is in neutral or park. I sometimes see LEAF Spy list 1, 2, or more weak cells and other times see it show all cells are OK when battery SOC is near VLBW or lower. So far, it has not set DTCs and there has been no power limitation (other than risk of sudden turtle mode or shutdown if high discharge rate is sustained long enough to keep minimum cell voltage low for too long). LEAF Spy did not show weak cells when I took the car in for the annual battery test in January so I was not surprised that Nissan did not do anything under the defect warranty--will see what happens next year. Regardless of whether LEAF Spy shows weak cells by module number or not, I can see from the cell pair voltage graphs that several modules located at the front of the battery are weak (very low voltage under load and higher voltage while charging compared to other cells). I will try to post some screen shots when I get a chance.
Gerry
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015; traded 8/10/2019 at 82,436 miles
White LEAF 2019 SL+ purchased 8/10/2019

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Marktm
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Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Thu Aug 15, 2019 2:08 pm

GerryAZ wrote:
Wed Jul 24, 2019 7:14 pm
Marktm's "weak cells" are not weak enough to be of concern at this time. For example, I had 363 mV difference last night on my way home. I also see VLBW come in with pack voltage above 360 volts (indicates a lot of energy is left in stronger cells). My experience is that results of CVLI tests are quite variable. LEAF Spy Pro performs the CLVI test whenever the average cell pair voltage is low enough to meet the guidelines in the service manual and the car is in neutral or park. I sometimes see LEAF Spy list 1, 2, or more weak cells and other times see it show all cells are OK when battery SOC is near VLBW or lower. So far, it has not set DTCs and there has been no power limitation (other than risk of sudden turtle mode or shutdown if high discharge rate is sustained long enough to keep minimum cell voltage low for too long). LEAF Spy did not show weak cells when I took the car in for the annual battery test in January so I was not surprised that Nissan did not do anything under the defect warranty--will see what happens next year. Regardless of whether LEAF Spy shows weak cells by module number or not, I can see from the cell pair voltage graphs that several modules located at the front of the battery are weak (very low voltage under load and higher voltage while charging compared to other cells). I will try to post some screen shots when I get a chance.
Has anyone seen evidence that the severely degraded 2011,12,13's will start setting the DTC and fail the CVLI test as the battery reaches end of life (2,3,4,5 bars)? If so, is there any way Nissan can back away from the warranty based on the "language". I'm simply wondering if the 10 year defect warranty might offer some "opportunities" for another round of replacements?
2012 Leaf SL; 43,000 miles. Battery replaced November 1st, 2016.

cwerdna
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Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Fri Aug 16, 2019 12:14 am

Marktm wrote:
Thu Aug 15, 2019 2:08 pm
Has anyone seen evidence that the severely degraded 2011,12,13's will start setting the DTC and fail the CVLI test as the battery reaches end of life (2,3,4,5 bars)? If so, is there any way Nissan can back away from the warranty based on the "language". I'm simply wondering if the 10 year defect warranty might offer some "opportunities" for another round of replacements?
What 10 year defect warranty? It's only 8 years/100K miles, whichever comes first.

Check your warranty booklet if you don't believe me.

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Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

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