The 40KWH Battery Topic

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As a side note, I have never charged the car above 85%. I've been keeping it between about 45% and 80% normally. Should I charge it to 100% once just to see the data?
 
Unless you have big range needs or have a real hankering to see the 100% data, I wouldn't bother. The time will likely come when you need to do it for a trip anyway.
 
Why did the Hx value in my 40 kWh start off in the mid 90's and now with a SOH of 95.70 the Hx is around 113. Is there any technical reason?
 
jdcbomb said:
Why did the Hx value in my 40 kWh start off in the mid 90's and now with a SOH of 95.70 the Hx is around 113. Is there any technical reason?

Yes there is a technical reason but specifics can only be supposed.

I "think" the change in chemistry and resulting change in resistance values has caused the higher than normal reading. My Hx has been between 118-119 for months now.
 
DaveinOlyWA said:
jdcbomb said:
Why did the Hx value in my 40 kWh start off in the mid 90's and now with a SOH of 95.70 the Hx is around 113. Is there any technical reason?

Yes there is a technical reason but specifics can only be supposed.

I "think" the change in chemistry and resulting change in resistance values has caused the higher than normal reading. My Hx has been between 118-119 for months now.

Nissan most likely didn't modify the algorithm that calculated Hx (the ratio of the battery's conductances - present/initial) based
on the later batteries, e.g. using the older batteries' initial conductance value which would cause Hx to be greater than 100%.
 
lorenfb said:
DaveinOlyWA said:
jdcbomb said:
Why did the Hx value in my 40 kWh start off in the mid 90's and now with a SOH of 95.70 the Hx is around 113. Is there any technical reason?

Yes there is a technical reason but specifics can only be supposed.

I "think" the change in chemistry and resulting change in resistance values has caused the higher than normal reading. My Hx has been between 118-119 for months now.

Nissan most likely didn't modify the algorithm that calculated Hx (the ratio of the battery's conductances - present/initial) based
on the later batteries, e.g. using the older batteries' initial conductance value which would cause Hx to be greater than 100%.

Are you sure that is the algorithm used to calculate Hx? I find it hard to imagine that while reprogramming the BMS for the new models that the value of the initial conductance (a constant) wasn't changed. As far as I know, no one here really knows what Hx means. Like the old adage "those that know don't say and those that say don't know". It will be interesting to see what happens to Hx values as the 40kWh and 60kWh packs age but practically speaking, what difference does it make? Does it affect charge rate, regen rate, or anything meaningful at all?
 
goldbrick said:
lorenfb said:
Nissan most likely didn't modify the algorithm that calculated Hx (the ratio of the battery's conductances - present/initial) based
on the later batteries, e.g. using the older batteries' initial conductance value which would cause Hx to be greater than 100%.

Are you sure that is the algorithm used to calculate Hx?

1. It appears to be a percentage, e.g. 0 - 100%.
2. It tracks SOH, i.e. declines as the battery ages.
3. It does agree with the inverse of the ratio of the battery resistance over time.
4. It provides additional insight into battery degradation over time.

My 2013 battery resistance over time:

12/27/14 - 14,800 miles, 103 mohms per LeafDD, 11 deg, 24% SOC
3/10 - 17,400 miles, 60 mohms per LeafDD, 30 deg, 73% SOC
3/14 - 17, 550 miles, 56 mohms per LeafDD, 32 deg, 47% SOC
4/14 - 19,100 miles, 59 mohms per LeafDD, 25 deg. 38% SOC
5/4 - 19,989 miles, 64 mohms per LeafDD, 24 deg. 48% SOC
5/15 - 20,400 miles, 73 mohms per LeafDD, 20 deg. 41% SOC
5/22 - 20,700 miles, 58 mohms per LeafDD, 28 deg. 50% SOC
12/10/15 - 28,000 miles, 90 mohms per LeafDD, 19 deg. 92% SOC
4/5 - 32,000 miles, 74 mohms per LeafDD, 24 deg, 55% SOC
5/16 - 33,700 miles, 89 mohms per LeafDD, 22 deg, 47% SOC
5/16 - 33.700 miles, 58 mohms per LeafDD, 31 deg, 76% SOC
10/5 - 39,300 miles, 100 mohms per LeafDD, 22 deg, 50% SOC
10/6 - 39,400 miles, 61 mohms per LeafDD, 30 deg, 51% SOC
10/7 - 39,500 miles, 80 mohms per LeafDD, 25 deg, 56% SOC
10/15 - 40,000 miles, 71 mohms per LeafDD, 27 deg, 45% SOC
10/30 - 41,000 miles, 74 mohms per LeafDD, 23 deg, 66% SOC
12/26/16 - 43,000 miles, 110 mohms per LeafDD, 13 deg, 77% SOC
6/10/17 - 49,600 miles, 89 mohms per LeafDD, 19 deg, 70% SOC
7/1/17 - 51,000 miles, 62 mohms per LeafDD, 33 deg, 44% SOC
8/15/17 - 53,400 miles, 61 mohms per LeafDD, 35 deg, 57% SOC
4/2/18 - 62,100 miles, 110 mohms per LeafDD, 18 deg, 94% SOC
6/13/18 - 65,000 miles, 84 mohms per LeafDD, 26 deg, 52% SOC
8/13/18 - 67,000 miles, 80 mohms per LeafDD, 26 deg, 91% SOC
9/14/18 - 68,000 miles, 84 mohms per LeafDD, 27 deg, 57% SOC

And you have a better assumption?
 
After 15 months of regular, fairly consistent decreases in SOH, LeafSpy has reported my first INCREASE in SOH. I started out at 93.95% on July 5th and ended the day at 94.09%. Yesterday it dropped the regular 0.01% to 94.08%. There was nothing significantly different about the driving or charging I did on the 5th - 49 km driven, pack temperature 20-22C, SOC near 50%, no charging. We don't have any L3 chargers within 500 km so I have never rapid charged it. It gets charged to 100% twice a week just prior to a 100 km trip.

Has anyone else seen an increase in SOH with a 40 kWh pack? I know it was common with 24 and 30 kWh packs, particularly after a rapid charge, but I have not read/heard about any 40 kWh packs that have shown an increase in SOH.

Degradation seems to have slowed significantly as the pack has aged. SOH dropped from 99.57% to 94.84% (4.73%) in the first 6 months with 12,000 km (7,500 mi) driven. In the 9 months since (includes 6 months of winter) I have driven 16,000 km (10,000 mi) with SOH only dropping from 94.84% to 94.08% (0.76%). If this trend continues, the longevity of the 40 kWh pack might be pretty good - at least in a cool/cold climate - and if you can trust the data provided by the BMS.
 
I haven't seen an increase, and haven't read of one before yours. My own experience was a disturbing drop in SOH the first 6 months, then virtually no drop over the first Winter and Spring, resulting in a first year drop of about 4.6%, IIRC. I haven't checked it this Summer.
 
SOH rise is unique. I have seen a single "point" (.01%) rise during the day that negated itself by the next morning (only record data in morning or before first drive of the day)

As far as my loss, its settled into a pattern of a relatively large chunk lost every 90 days. Because of this rather predictable pattern, I have varied both charging and driving habits to see if anything affected this 90 day cycle and nothing has so far.

I am a few days to maybe a week to my next "adjustment" so we shall see what happens.
 
DougWantsALeaf said:
So the 40 KW battery is degrading at the same rate as earlier batteries?

My conclusion, subject to change with more data, is that the 40kwh pack degrades much like the Wolf Pack (4/'13 - 2014): it doesn't degrade fast if kept cool but does if kept hot. It may be more sensitive to moderately high temps than the Wolf pack, which if true means that multiple QC sessions should be avoided in warm weather...
 
I was expecting a larger than normal reduction in SOH about now, but instead I got a .34% increase over the last 2 days.

No 100% charges in the last 6 months. Been charging to 65% once reaching about 20%. It has been hot here in Atlanta for the last few months.

I'll give the specifics if I can't get the images to show.


BBDq

BEnG




https://drive.google.com/file/d/18ZTVyHLuTaSVhzJRYlGO19BruyhddYC8/view?usp=sharing
https://drive.google.com/file/d/1kY6FMZhFg3VgATCTkmwfHsjQVTv8tJ4a/view?usp=sharing
 
I will add my car to the list of 2018's that have had battery stats go up (for the first time). I am now at a level that matches my stats from April 8th (a period when ahr went from 107.24 to 106.18 in 5 days) I am now at 107.01

So guessing BMS "overestimated my driving for April to July (which did happen slightly especially in June from 3 short vacations of 2-3 days and one medium one 7 days)
 
It will be interesting to see if this reversal continues to happen. Mine was pushed back to April 23rd.

My 3 month rolling loss not counting this last upward correction since Feb has dropped to .8% last year it was almost 2.5%
 
LeftieBiker said:
DougWantsALeaf said:
So the 40 KW battery is degrading at the same rate as earlier batteries?

My conclusion, subject to change with more data, is that the 40kwh pack degrades much like the Wolf Pack (4/'13 - 2014): it doesn't degrade fast if kept cool but does if kept hot. It may be more sensitive to moderately high temps than the Wolf pack, which if true means that multiple QC sessions should be avoided in warm weather...
My conclusion about the 'Wolf' pack is that the range of experiences is wide. It would not surprise me if the 40 kWh pack fairs similarly ... which would actually be good news since it is a bigger pack and carries a longer warranty than the 24 kWh LEAFs. I would not care to play the LEAF lottery with a new car purchase but it does suggest that informed purchase of a well behaving 40 kWh LEAF coming off lease would be reasonable for gentle use in non-hot climates.

This is my pampered 'Wolf' pack over the past 27 months, which I think fits in the well behaved group -- for LEAF, anyway.
The initial loss seen in the graph is actually the tail of a 10% loss in capacity after I bought the car, I presume part of a reset calibration.

uc
 
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