2016-2017 model year 30 kWh bar losers and capacity losses

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The study notes that loss goes down with higher mileage, which doesn't make sense for heat. The more you drive, the hotter the batteries, the faster the capacity loss.

Remember that the only cooling these packs have is passive: air blows over the case while driving. I suspect that this is the same issue as cars using V2H having more degradation, in that the less you drive after charging, the hotter the pack stays and the more it degrades.
 
So if it’s a heat from charging thing would it be a good idea to lower charge currents. We generally charge outside but it can get hot here in summer. Maybe even 120 volt 12 amp charging. Charging overnight slowly is not an issue for us.

Thanks for any opinions.

John.
 
webeleafowners said:
So if it’s a heat from charging thing would it be a good idea to lower charge currents. We generally charge outside but it can get hot here in summer. Maybe even 120 volt 12 amp charging. Charging overnight slowly is not an issue for us.

That may be true...but only after a certain point. The "C" rate charging @L2 in most residences (I have a 30a feed) is not much worse than L1 rates. In other words, might as well keep charging @L2 @home.
 
LeftieBiker said:
The study notes that loss goes down with higher mileage, which doesn't make sense for heat. The more you drive, the hotter the batteries, the faster the capacity loss.

Remember that the only cooling these packs have is passive: air blows over the case while driving.

And remember that 24kWh packs show more loss with higher mileage, which makes sense both for cycle wear out and for heat. The 30kWh packs show the reverse. Why?

When I put 150 miles on my car in a day, the battery gets a lot toastier.
 
webeleafowners said:
So if it’s a heat from charging thing would it be a good idea to lower charge currents. We generally charge outside but it can get hot here in summer. Maybe even 120 volt 12 amp charging. Charging overnight slowly is not an issue for us.

Thanks for any opinions.

John.

It would be interesting if a battery resistance comparison were made between a 24kWh battery and a 30kWh battery.
Below are my Leaf resistance values taken over the years using the LeafDD BMS reader. LeafSpy also provides the
Leaf's battery resistance.

12/2 - 14.100 miles, 55 mohms per LeafDD, 28 deg, 67% SOC
12/16 - 14,500 miles, 89 mohms per LeafDD, 15 deg, 93% SOC
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

One would expect, given the higher kWhs output of the 30kWh battery verses the 24kWh battery, that the output resistance should
be lower, i.e. more parallel cells. If the resistance is higher, e.g. different chemistry/supplier, then when charging and driving,
the 30kWh battery will always be hotter than the 24kWh battery. As noted from my data, the battery resistance has a negative
temp coefficient, offsetting some of the additional potential power dissipation.
 
WetEV said:
LeftieBiker said:
The study notes that loss goes down with higher mileage, which doesn't make sense for heat. The more you drive, the hotter the batteries, the faster the capacity loss.

Remember that the only cooling these packs have is passive: air blows over the case while driving.

And remember that 24kWh packs show more loss with higher mileage, which makes sense both for cycle wear out and for heat. The 30kWh packs show the reverse. Why?

When I put 150 miles on my car in a day, the battery gets a lot toastier.

The 30kwh packs seem to show the reverse because there is something badly wrong in the chemistry, as I now see it - something much worse than anything that was ever present in the 24kwh packs. Not only do they seem to suffer more damage over a shorter time, but the damage seems to accelerate. As I wrote earlier, I suspect that it's the accumulation of destructive reaction byproducts, with no way for them to be removed or transformed.

Your driving circumstances make your battery get hot, but not everyone else's does. On one of my typical non-Summer trips, the bar temp display stays unchanged. So miles added that heat the pack add to degradation. Miles added that don't significantly heat the pack may have no negative effect at all.
 
LeftieBiker said:
WetEV said:
LeftieBiker said:
Remember that the only cooling these packs have is passive: air blows over the case while driving.

And remember that 24kWh packs show more loss with higher mileage, which makes sense both for cycle wear out and for heat. The 30kWh packs show the reverse. Why?

When I put 150 miles on my car in a day, the battery gets a lot toastier.

The 30kwh packs seem to show the reverse because there is something badly wrong in the chemistry, as I now see it

I'm not a real battery expert, so would you please explain and provide references to some similar issue? I've been an electrical engineer working on multiple battery powered projects, however not directly on the battery, and I've never heard of such an issue. Evidence, please.


LeftieBiker said:
Your driving circumstances make your battery get hot, but not everyone else's does.

Everyone's battery mostly warms while driving, unless it starts out at roughly 10C or more warmer than the air temperature. The more you drive, or the faster you drive, the more the pack warms. Yes, there is a range of discharge that absorbs heat, so it might be possible to cool the pack a tiny amount over a short, slow drive. Even to below ambient, which would be weird. Probably other strange effects as well.

Usually, however, driving and charging both warm the battery pack. The more driving and charging you do, the more the pack warms.

Example: A recent 18.7 mile drive of mine at ambient temperatures between 37F and 32F, starting at 77% SOC and ending at 47% SOC. Battery temperatures started at 43.8F to 47.6F and ended at 45.4F to 49.8F. Average speed was 33.8 mph. Fairly flat, near sea level. Data as recorded by Leafspy Pro.


LeftieBiker said:
On one of my typical non-Summer trips, the bar temp display stays unchanged.

The bat temperature display is very coarse and has a lot of hysteresis, so is hard to see much.


LeftieBiker said:
So miles added that heat the pack add to degradation. Miles added that don't significantly heat the pack may have no negative effect at all.

Even a cold battery degrades with cycle count.
 
WetEV said:
Usually, however, driving and charging both warm the battery pack. The more driving and charging you do, the more the pack warms.

P (internal battery power - heat) = I ^2 (battery current) X R (internal battery resistance)

P (total vehicle power consumed) = RR (rolling resistance - k X V) + DL (drag losses - k X V^3) = I (battery current) X 400 (battery voltage)

From above, it becomes obvious that for every incremental increase in speed an incremental increase in power in required.
But since the battery voltage is constant, the battery current increases resulting in the battery power (heat) increasing exponentially
( I^2 X R ) as the speed increases. This is further compounded by the DL factor at higher and higher speeds.

The same battery heating effect (I^2 X R) occurs while charging, i.e. the longer the charging time the greater will be the increase
in battery temp. This becomes more problematic with long QCs and higher QC currents.
 
WetEV said:
joeriv said:
A great study!

After reading it I think there are two factors at play:

1. The battery chemistry is different.
2. The packaging for the cells was changed (not mentioned in the study).

I suggest a third factor to consider.

I think that there might be a problem in the charging and/or balancing algorithm(s). Maybe due to a change in the charger/BMS, maybe due the change in chemistry that requires a slightly different charging and/or balancing algorithm(s).

The study notes that loss goes down with higher mileage, which doesn't make sense for heat. The more you drive, the hotter the batteries, the faster the capacity loss.

Both this study and other things I've heard suggest that cars that are driven a lot are doing better.


joeriv said:
If the trends in the study are indicative of things to come, Nissan will be replacing lots of batteries and the 40 may show similar degradation. Nissan will have to make some mods to chemistry and/or packaging to avoid future expensive warranty claims.

Yes, Nissan will be replacing a lot of batteries. Hopefully they will find and fix the issue, which might not be chemistry or packaging, but electronics/firmware.


Agreed the graph is one dimensional.

Also agree that BMS has issues. I HIGHLY doubt its the batteries. Using time only on a graph doesn't say how much the car was driven, time spent at high SOC or really any other factor.

What is does say is that Nissan failed to provide basic BMS operation that would lessen any negative impact by the customer. A monumental oversight.

America is overrun by products redeveloped due to a litigation of one sort or another and many were rooted in situations were lives and livelihoods were on the line.

Sadly, despite overwhelming evidence that we simply do not know how to manage our packs, Nissan has failed to idiot proof the process like EVERY EV manufacturer has done.


FYI; On my LEAF, I am seeing over 98% SOC to full charge if car is driven within 30 mins of charge completion. Something I have managed to do 4 times (due to before 4 AM departures... :( )

On other days when the charge cycle completed several hours before departure, I am seeing SOC's in the high 96's or low 97's


To have this as not only the default but the ONLY setting is simply...
 
DaveinOlyWA said:
What is does say is that Nissan failed to provide basic BMS operation that would lessen any negative impact by the customer. A monumental oversight.

Like what?
 
lorenfb said:
DaveinOlyWA said:
What is does say is that Nissan failed to provide basic BMS operation that would lessen any negative impact by the customer. A monumental oversight.

Like what?
??

Did you read my post?

How about charging to 99.5%? Is that ok too?

http://daveinolywa.blogspot.com/2018/02/2018-leaf-week-one-ups-and-yes-downs.html


Examine the LEAF Spy log....
 
DaveinOlyWA said:
lorenfb said:
DaveinOlyWA said:
What is does say is that Nissan failed to provide basic BMS operation that would lessen any negative impact by the customer. A monumental oversight.

Like what?
??

Did you read my post?

How about charging to 99.5%? Is that ok too?

http://daveinolywa.blogspot.com/2018/02/2018-leaf-week-one-ups-and-yes-downs.html


Examine the LEAF Spy log....

That's been discussed before and concluded that it has an insignificant effect relative to other factors, e.g. battery heat, cycles, age.
There's a whole thread devoted to that discussion with detailed graphs!
 
lorenfb said:
DaveinOlyWA said:
lorenfb said:
Like what?
??

Did you read my post?

How about charging to 99.5%? Is that ok too?

http://daveinolywa.blogspot.com/2018/02/2018-leaf-week-one-ups-and-yes-downs.html


Examine the LEAF Spy log....

That's been discussed before and concluded that it has an insignificant effect relative to other factors, e.g. battery heat, cycles, age.
There's a whole thread devoted to that discussion with detailed graphs!

Ohhhh.... ok. So u r in "that" camp.

Got it!
 
DaveinOlyWA said:
??
Did you read my post?
How about charging to 99.5%? Is that ok too?
http://daveinolywa.blogspot.com/2018/02/2018-leaf-week-one-ups-and-yes-downs.html
Examine the LEAF Spy log....
The 2018 pack is being charged to 4.2V with different chemistry to the 2016-17 which I believe top out around 4.12V. The regen when nearly full is when less than 4.2V and I suspect will be limited to 4.2V so probably ok. I don't think the 40kWh details are very relevant for the 30kWh but still interesting.
 
dwl said:
DaveinOlyWA said:
??
Did you read my post?
How about charging to 99.5%? Is that ok too?
http://daveinolywa.blogspot.com/2018/02/2018-leaf-week-one-ups-and-yes-downs.html
Examine the LEAF Spy log....
The 2018 pack is being charged to 4.2V with different chemistry to the 2016-17 which I believe top out around 4.12V. The regen when nearly full is when less than 4.2V and I suspect will be limited to 4.2V so probably ok. I don't think the 40kWh details are very relevant for the 30kWh but still interesting.

hmmm...

sorry but I don't believe a word of what you have to say after "so"
 
DaveinOlyWA said:
dwl said:
The 2018 pack is being charged to 4.2V with different chemistry to the 2016-17 which I believe top out around 4.12V. The regen when nearly full is when less than 4.2V and I suspect will be limited to 4.2V so probably ok. I don't think the 40kWh details are very relevant for the 30kWh but still interesting.

hmmm...

sorry but I don't believe a word of what you have to say after "so"
If the cell voltage doesn't rise above the maximum of 4.2V on the 40kWh chemistry I don't see why there is an issue if regen is allowed below this. I should have said I don't think the 40kWh details are relevant to this thread which is about 30kWh bar losers - sorry if I caused confusion.
 
WetEV said:
Yes, Nissan will be replacing a lot of batteries. Hopefully they will find and fix the issue, which might not be chemistry or packaging, but electronics/firmware.

I've lost hope that Nissan are even trying to resolve the issue anymore. Let's face it, poor battery degradation has been present since the first car came off the production line in 2010. If after 8 years they haven't figured it out, they either are incompetent or simply dealing with the issue until they can get someone else (eg LG) to make the batteries for their cars. If the fix was simply electronics/firmware they would have taken care of the issue a long time ago.

The advantage for Nissan with going 3rd party is that they will recover any warranty costs from the OEM rather than have to continually eat the costs themselves. By selling the battery factories Nissan may have achieved that financial goal already.
 
Levenkay said:
JPWhite said:
If the fix was simply electronics/firmware they would have taken care of the issue a long time ago.
Oh?? Have you tried using a LEAF's Nav system?

There is a lot more at stake when comparing a major drive train component to an optional feature.

There is a strong financial motive for Nissan to resolve this to avoid warranty costs. If it was relatively simple to fix it would be done already. Clearly there is something fundamental wrong with the battery or design of the system that isn't easy to overcome and Nissan have opted to absorb the warranty cost instead of fixing the issue.
 
JPWhite said:
I've lost hope that Nissan are even trying to resolve the issue anymore. Let's face it, poor battery degradation has been present since the first car came off the production line in 2010.

The lizard battery(late 2013 to 2016 24kWh) is pretty good. If the 30kWh battery was similar, few would be complaining.

JPWhite said:
If the fix was simply electronics/firmware they would have taken care of the issue a long time ago.

The problem with the 30kWh battery is different than the problems with early 24kWh batteries. Batteries, regeneration, charging and balancing are all fairly complex. The fact that simply driving more seems to improve lifetime suggests to me that a firmware change could make a large difference in battery life.


JPWhite said:
The advantage for Nissan with going 3rd party is that they will recover any warranty costs from the OEM rather than have to continually eat the costs themselves. By selling the battery factories Nissan may have achieved that financial goal already.

Not if the OEM can prove that Nissan's other electronics is shortening the life of the batteries.
 
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