The 40KWH Battery Topic

[DaveinOlyWA]

Olymipia Dave, on reddit there is someone who claims their 40 Leaf lost 2 bars. They traded the car in, and have no photos, so not sure how credible, but it is a report.

https://www.reddit.com/r/leaf/comments/jlw9w7/nissan_leaf_beats_bmw_i3_and_tesla_model_s_in/?utm_medium=android_app&utm_source=share

Interesting. No details so only guessing but sounds like he only DC'd a few times a week. Probably charged to too high an SOC in heat is my guess. Not really enough here to do anything with. Let me know if he has any details like VIN dash pix, etc

 

[danrjones]

So I have noticed an interesting trend. Since peaking early summer my HX has been dropping like a rock. I know we still have no idea if HX even means anything, but still interesting.

Whether it lags summer heat or Winter Cold, or has something to do with my battery or charging habit? I used to charge to about 80% +/- but I dialed that down to around 70% some months back. No need to charge that high, so I don't.

On 5/19/2020 my HX peaked at 109.17.

As of this AM, its dropped down to 105.24.

Too bad I don't know if that's a good or bad thing! LOL

 

[lorenfb]

So I have noticed an interesting trend. Since peaking early summer my HX has been dropping like a rock. I know we still have no idea if HX even means anything, but still interesting.

No idea, really? There've been numerous threads on Hx with data.

Whether it lags summer heat or Winter Cold, or has something to do with my battery or charging habit? I used to charge to about 80% +/- but I dialed that down to around 70% some months back. No need to charge that high, so I don't.

On 5/19/2020 my HX peaked at 109.17.

As of this AM, its dropped down to 105.24.

You haven't included the actual temperatures at the data points. You do realize temperature is a key battery parameter?

 

[danrjones]

So I have noticed an interesting trend. Since peaking early summer my HX has been dropping like a rock. I know we still have no idea if HX even means anything, but still interesting.

No idea, really? There've been numerous threads on Hx with data.

Whether it lags summer heat or Winter Cold, or has something to do with my battery or charging habit? I used to charge to about 80% +/- but I dialed that down to around 70% some months back. No need to charge that high, so I don't.

On 5/19/2020 my HX peaked at 109.17.

As of this AM, its dropped down to 105.24.

You haven't included the actual temperatures at the data points. You do realize temperature is a key battery parameter?

Yes, numerous threads, where most people agreed that for 2018 and on, they had no idea if HX meant the same as it did on the previous models.

HX changes very slowly, so including the temperature at one moment in time would not be a proper snapshot. Do I include morning temp or evening temp? Where I live, my battery can change 20-30 degrees over the course of a 24 hour period. For a big chunk of the year - May to October, the battery is almost always above 90f and often above 100f. But again, that varies significantly during the course of a 24 hour period, as my car sits in both the sun and the moon.

So you would end up in a 24 hour period with two vastly different temp readings and the same HX reading. That doesn't sound helpful. I'd have to find the average battery temp at the correct time of day, or take multiple readings per day and calculate the average temp, and that's more work and time than I have.

 

[OrientExpress]

No idea what Hx is? You aren’t alone, even the creator of LEAFSpy is not sure what it is.

Here is a quote from him on the meaning of Hx

“ Hx
The meaning of this number is not fully understood but it appears to be inversely related to the battery internal resistance. As the internal resistance of the battery pack increases it is thought this percentage decreases. As internal resistance increases more energy is lost within the pack and the pack heats up more under load.”

 

[danrjones]

Yes, the rumor is that it is internal resistance but other folks here said the data for HX changed dramatically for 2018 and beyond, possibly because Nissan changed what it meant.

Anyway, my HX readings are what they are, whatever they are! Just an interesting trend.

 

[lorenfb]

Yes, the rumor is that it is internal resistance but other folks here said the data for HX changed dramatically for 2018 and beyond, possibly because Nissan changed what it meant.

Rumors lack veracity! Your Hx longitudinal data are here; https://mynissanleaf.com/viewtopic.php?f=9&t=25773&start=920#p591935
It has a very small negative slope over time.

For Leaf1, longitudinal data indicate the Hx tracks SOH, i.e. declines with battery degradation. Longitudinal data also indicate
that the actual battery resistance increases with battery degradation. One can then conclude for Leaf1, Hx does not represent
battery resistance, but it represents battery conductance.

With regard to Leaf2, Hx for one of the oldest (40 kWh, 2+ yrs) indicated the Hx had a positive slope over time, which results
its being a battery resistance value. Obviously that single sample is anecdotal. Therefore more data are required for any
conclusion about Leaf2's Hx. The data for this sample is here;
https://mynissanleaf.com/viewtopic.php?f=9&t=25773&start=920#p592021

 

[danrjones]

Yes, the rumor is that it is internal resistance but other folks here said the data for HX changed dramatically for 2018 and beyond, possibly because Nissan changed what it meant.

Rumors lack veracity! Your Hx longitudinal data are here; https://mynissanleaf.com/viewtopic.php?f=9&t=25773&start=920#p591935
It has a very small negative slope over time.

For Leaf1, longitudinal data indicate the Hx tracks SOH, i.e. declines with battery degradation. Longitudinal data also indicate
that the actual battery resistance increases with battery degradation. One can then conclude for Leaf1, Hx does not represent
battery resistance, but it represents battery conductance.

With regard to Leaf2, Hx for one of the oldest (40 kWh, 2+ yrs) indicated the Hx had a positive slope over time, which results
its being a battery resistance value. Obviously that single sample is anecdotal. Therefore more data are required for any
conclusion about Leaf2's Hx. The data for this sample is here;
https://mynissanleaf.com/viewtopic.php?f=9&t=25773&start=920#p592021

I'm more than willing to run with the idea that HX for the 2018 is a direct measure of resistance - so lower is better. My data shows two humps, a small one followed by a larger one, but I can't really correlate them to anything. The first hump peaked in late august of 2019 and then starts declining the second hump peaked in this May and has since been on a bigger decline. So those don't jive with seasonal temperature directly.

 

[lorenfb]

I'm more than willing to run with the idea that HX for the 2018 is a direct measure of resistance - so lower is better.

For Leaf1 Hx was a ratio, not an actual value, with an initial value of 100, as was SOH.

My data shows two humps, a small one followed by a larger one, but I can't really correlate them to anything. The first hump peaked in late august of 2019 and then starts declining the second hump peaked in this May and has since been on a bigger decline. So those don't jive with seasonal temperature directly.

Actually, there's some info that your data provides since 6/5/20, i.e. SOH and HX have been correlated as both have been declining.
Assuming that Hx is ratio of some parameter that changes relative to its initial value, and that battery resistance typically increases as the
battery degrades, one would conclude that your data is now tracking the Leaf1 Hx, where Hx is the ratio of battery conductance and
not battery resistance. Given that your data for SOH changes are very small, any conclusions without additional longitudinal data are marginal.

 

[danrjones]

I'm more than willing to run with the idea that HX for the 2018 is a direct measure of resistance - so lower is better.

For Leaf1 Hx was a ratio, not an actual value, with an initial value of 100, as was SOH.

My data shows two humps, a small one followed by a larger one, but I can't really correlate them to anything. The first hump peaked in late august of 2019 and then starts declining the second hump peaked in this May and has since been on a bigger decline. So those don't jive with seasonal temperature directly.

Actually, there's some info that your data provides since 6/5/20, i.e. SOH and HX have been correlated as both have been declining.
Assuming that Hx is ratio of some parameter that changes relative to its initial value, and that battery resistance typically increases as the
battery degrades, one would conclude that your data is now tracking the Leaf1 Hx, where Hx is the ratio of battery conductance and
not battery resistance. Given that your data for SOH changes are very small, any conclusions without additional longitudinal data are marginal.

Actually my SOH jumped up for the first time in my last 3 month adjustment in Sept and the daily drop has almost stopped, right now with the cooler weather. My current SOH is higher than it has been since end of may. I have all my data plotted and their is no apparent correlation between my SOH and HX.

 

[DaveinOlyWA]

My Hx take.

2018, Hx changed. There is no doubt in my mind about that. Mine (both 2018 and 2019 did nearly the same) started in the high 90's and slowly moved into the mid 100's staying for a while then as Summer approached, they skyrocketed into the lower 120's. This also included a lot more DC charging usage. During this point, I was seeing my largest downward adjustments. Then, the Hx started dropping a bit. On the 2018, it was down to 114 from a high of 121.79, The last two adjustments were plus 1.12% and zero.

Now my 2019 due to COVID, didn't DC nearly as much as several planned trips were cancelled so Hx peaked at 117.85 and DC charging slowed down considerably due to no NCTC, etc. My last adjustment was .37% drop which is the smallest by far and I am in the mid 113's now. Its my prediction my next adjustment will be zero or positive.

So what does this mean? DK other than two other LEAFers have Hx either just below or just above 100 and are over 100,000 miles still 12 capacity bars.

At this point, I don't know if the Hx drop has to do with lack of DC charging as the number bounces up and down a lot but did see most of the major jumps (as much as .63% in a day) happened on days when DC charging occured.

 

[lorenfb]

I'm more than willing to run with the idea that HX for the 2018 is a direct measure of resistance - so lower is better.

You can do this procedure to get an idea of the value for the dynamic (impulse function) resistance of your battery;
https://mynissanleaf.com/viewtopic.php?f=9&t=28911&hilit=resistance&start=320#p559503

 

[Jollermd]

My second leaf, and I drive it hard and pay not much attention to it. Home charger . Came to this site as close to needing new tires for the Chicago winter. My range seems to be holding, the % battery charge remaining on guess-o-meter is not linear. From 100% my first commute uses 23 - 25%. Next day I use 30 -35% on same trip!

Here are my stats. I really am concerned as numbers dropping lot faster than my 2015.. 24kw leaf did. , HX sudden drop How am I doing????
DATA corrected for error

Date...... ODO......; Ahr.; SOH; SOC; hx.; "GIDS" kwh
4/01/2018 00960 114.8 99.5 96.6 106.9 490 38.0
9/29/2018 08496 111.6 96.7 99.1 108.2 489 37.9
8/24/2019 19503 107.8 93.3 98.9 100.5 472 36.5
1/15/2020 23660 106.9 92.6 95.8 99.18 453 35.1
11/6/2020 32250 103.2 90.1 99.2 87.3 456 35.3

 

[cwerdna]

My second leaf, and I drive it hard and pay not much attention to it. Home charger . Came to this site as close to needing new tires for the Chicago winter. My range seems to be holding, the % battery charge remaining on guess-o-meter is not linear. From 100% my first commute uses 23 - 25%. Next day I use 30 -35% on same trip!

Here are my stats. I really am concerned as numbers dropping lot faster than my 2015.. 24kw leaf did. GIDS down 20%, HX sudden drop How am I doing????

Date...... ODO......; Ahr.; SOH; SOC; hx.; "GIDS" kw
4/01/2018 00960 114.8 99.5 96.6 106.9 490 38.0
9/29/2018 08496 111.6 96.7 99.1 108.2 489 37.9
8/24/2019 19503 107.8 93.3 98.9 100.5 472 36.5
1/15/2020 23660 106.9 92.6 95.8 99.18 453 35.1
11/6/2020 30250 103.2 90.1 99.2 87.3 403 35.3

For the bolded portions, you talking about kWh?

Battery capacity and energy are measured in kWh, not "kw".

 

[LeftieBiker]

So you have an early build 2018 40kwh Leaf? I don't know that bad cells (which have been an issue with these cars) will lower the SOH like that, but give us the X mv difference, as provided by LeafSpy Pro, between the lowest and highest cell anyway.

 

[Jollermd]

I posted correction , had the GIDS wrong and changed kw to kw/h.

Yes it was one of the first 2018 delivered in late Feb.

to answer the voltage question is see:

min/ave/max of 4.203 / 4.203/4.206 (3mv)

 

[DaveinOlyWA]

My second leaf, and I drive it hard and pay not much attention to it. Home charger . Came to this site as close to needing new tires for the Chicago winter. My range seems to be holding, the % battery charge remaining on guess-o-meter is not linear. From 100% my first commute uses 23 - 25%. Next day I use 30 -35% on same trip!

Here are my stats. I really am concerned as numbers dropping lot faster than my 2015.. 24kw leaf did. , HX sudden drop How am I doing????
DATA corrected for error

Date...... ODO......; Ahr.; SOH; SOC; hx.; "GIDS" kw/h
4/01/2018 00960 114.8 99.5 96.6 106.9 490 38.0
9/29/2018 08496 111.6 96.7 99.1 108.2 489 37.9
8/24/2019 19503 107.8 93.3 98.9 100.5 472 36.5
1/15/2020 23660 106.9 92.6 95.8 99.18 453 35.1
11/6/2020 30250 103.2 90.1 99.2 87.3 456 35.3

Hx is unusually low. Most I see are well over 100. If your car follows the pattern, your degradation rate should slow way down. Expect 1-1.5% a year or so.

What are your charging/driving habits? Looks like your needs are quite modest. What is your target SOC when you charge?

 

[Jollermd]

I charge after midnight, when rates are super low. I don't have ability to control charge as my Clippercreek is not programmable and as far as I know nor is the car, so charge to 100%. It seems the battery can spend a lot of time at 95%+. I assume its doing something to renew the battery. Anyone else notice that?

I drive mostly hwy, with COVID traffic around 60-75 mph. Flat the pedal plenty. Occasional 90 mile trip on hwy to beach cabin, 60 to 80mph with COVID traffic. (speed limit 70)

date..... charges qc
4/1/2018 031 04
9/29/2018 226 12
8/24/2019 539 18
1/15/2020 684 19
11/6/2020 958 22

 

[LeftieBiker]

The car tries to balance the pack as it nears full. This is called "top balancing." From that very small voltage difference I deduce two things: that the pack is very well balanced, likely with no bad cells, and that it is being charged to full too often for the pack's health. This still leaves the mystery of the rapidly dropping SOH...

 

[SageBrush]

Here are my stats. I really am concerned as numbers dropping lot faster than my 2015.. 24kw leaf did. , HX sudden drop How am I doing????
Date...... ODO......; Ahr.; SOH; SOC; hx.; "GIDS" kWh
4/01/2018 00960 114.8 99.5 96.6 106.9 490 38.0
9/29/2018 08496 111.6 96.7 99.1 108.2 489 37.9
8/24/2019 19503 107.8 93.3 98.9 100.5 472 36.5
1/15/2020 23660 106.9 92.6 95.8 99.18 453 35.1
11/6/2020 30250 103.2 90.1 99.2 87.3 456 35.3

About 10% battery capacity loss.
If you want to slow degradation, reduce the time the battery sits at a high SoC

By the way, energy is written in kWh ("kilowatt hours"), not kw/h