Li-ion cells cycle ageing

Jan-Erik-86 said:

Simply the fact that you ask this about the GA, makes it clear that it needs to be tested by more people, yes.

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Considerating Hillhater's GA post on your 14S Thread another test isn't necessary by docware as also supported by Pajda. Hillhater's following comment supports docware's exacting cycle ageing research test (GA graph) ..."https://endless-sphere.com/forums/download/file.php?id=261802" ...

Hillhater said:

I have packs of GA cells 10s, 4P, and have no problems or complaints.
.. But, i do not run much more than 2C, and i am not a daily user/ charger , so no experience with cycle life etc.
However, i have seen comments on this forum from other GA users who have reported poor cycle life with heavy use.

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On a positive note from the looks of docware's M36 graph, Erik is smiling with his final choice of M36 for his 14S Vruzend pack. :thumb:

docware said:

Pajda, I know that you are very experienced in this area, therefore I assumed that maybe you know something more, than you want or can share. I know you as a realistic guy who after all these experiences trust only verified facts. Also understand your Panasonic PD argument, however, exist any study on any cell which has different conclusions on calendar ageing ?

I agree that each cell is different and also probably can have different calendar ageing characteristics, just wanted to remind that there is another aspect of ageing except cycle ageing. We just miss more reports on various cells.

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Docware, Pajda and others are providing a significant contribution to this ES ebiking Battery forum ... ... (me not so much)

Pajda said:

The cycle life test results of GA measured by docware are valid. I got the similar results on more than dozen samples from different batches. So if you do not believe them, why are you asking for other cell test results?

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Happy Trails and Holidays to all,
eMark

doc: do you already have 250cycles data for 29E and GA as well? :wink:

Currently have 300 cycles finished on PF, M36 and GA, waiting for 29E 250 cycles to have all data together, will post during weekend.

Another batch of the charts. PF, M36 and GA after 300 cycles, 29E 250cycles.
DCIR range is unified for easier comparison but still sensitive enough for displaying DCIR changes. Some bigger variation on capacity curves are probably caused by higher temperature variation toward down. All cells and equipment are on the table near the window and lower outside temperatures invoke higher temperature variation inside the room during occasional ventilation.
Panasonic PF keeps worsing trend, both capacity and DCIR.
GA DCIR rise has nearly stopped, capacity decrease continues.
Both M36 and 29E are good, both in capacity retention and DCIR.

docware said:

Another batch of the charts. PF, M36 and GA after 300 cycles, 29E 250cycles.
DCIR range is unified for easier comparison but still sensitive enough for displaying DCIR changes. Some bigger variation on capacity curves are probably caused by higher temperature variation toward down. All cells and equipment are on the table near the window and lower outside temperatures invoke higher temperature variation inside the room during occasional ventilation.
Panasonic PF keeps worsing trend, both capacity and DCIR.
GA DCIR rise has nearly stopped, capacity decrease continues.
Both M36 and 29E are good, both in capacity retention and DCIR rise.

Panasonic PF 300 cycles.jpg
LG M36 300 cycles.jpg
Sanyo GA 300 cycles.jpg
Samsung 29E 250 cycles.jpg

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Thanks for the hard work

Yes very valuable contributions to the community.

It would be tedious, but #cycles to get to 70% SoH would be a great real-life metric.

Studies like this https://www.nrel.gov/docs/fy18osti/70616.pdf

use 80% but it seems many consumers push EoL past that point, even though the risks of catastrophic failure increase geometrically.

hi doc, thank you for updated graphs. Just few remarks:

1. I will recommend to periodically update graphs only in the first post of this topic and only "bump" that there is an update available. This partial result graphs become obsolete imediatelly after you add updated one. For someone who find this topic for the first time it is always dilema if it is worth to read all the posts for getting more informations.

2. I suggest to add into the Samsung graph title informaton, that it is 29E7 version.

3. I thought that your initial setting for both HE cells LG and Sanyo was 4.1V-3.4V but in this last update you have range down to 3.3V for LG M36, I think it is a typo.

I understand your point, on the other hand we will loose contact between the graphs and written posts. Maybe we will find some optimal solution.
E7 and 3,4 V - modified.

So it appears that 29e has a similar to PF capacity trend downwards ,but starts off higher at the same load ,maintains a much lower DCIR, and appears to be a much better choice based on that. M36 appears to be clearly far superior to them all , and GA appears to be utter garbage in comparison . The lithium manganese cells seem to hold their crap together better than the lithium cobalt variants do. Am I missing anything ?

I bought a batch of lg mh1. Any chance to chart that out?

Thanks

Dak77 said:

So it appears that 29e has a similar to PF capacity trend downwards ,but starts off higher at the same load ,maintains a much lower DCIR, and appears to be a much better choice based on that. M36 appears to be clearly far superior to them all , and GA appears to be utter garbage in comparison . The lithium manganese cells seem to hold their crap together better than the lithium cobalt variants do. Am I missing anything ?

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Yes, you are.
We are not comparing absolute capacity, we are looking at capacity decline comparing to starting value. By setting interval 4,1V - 3,4 V for high energy cells and 4,1 - 3,3 V for 2 900 mAh cells I was trying to get the same capacity. It worked for PF and M36. I´m not sure why GA and 29E7 are so different. One reason may be that GA is little bit old while 29E7 is fresh new. Another may be different capacity distribution, 29E7 has nearly zero capacity bellow 3,1 V.


Another aspect is that we are testing cells at specific conditions. Milder testing conditions, for example 50% DOD, 0,8 A charge, 2 A discharge, would show different picture, probably more positive for GA. Testing at rougher conditions would show another different result. Again, we have to keep on mind that the results are related to the specific testing parameters.

cwah said:

I bought a batch of lg mh1. Any chance to chart that out?

Thanks

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LG product MH1 together with MJ1 is surely another interesting cell for testing.

docware said:

cwah said:

I bought a batch of lg mh1. Any chance to chart that out?

Thanks

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LG product MH1 together with MJ1 is surely another interesting cell for testing.

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if you once fall into battery testing addiction, you fill find that every cell on the market is interesting until you got at least some initial data which tells you that it is a piece of shit. Then one day you figure out, that you are running 30 different cells test in average at the same time for 24/7 and still it is not enough...

Now something state-forming. LG MH1 is excellent cell in terms of cycle life, very close to M36 under many test settings. The only drawback is its higher DCIR, which starting at 45mOhm (DCR 10s value) where M36 starting at 36mOhm (DCIR 10s), MH1 is used by many well known ebike battery producers for its price-performance ratio.

Is resistance an important factor for anything other than C-rates?

john61ct said:

Is resistance an important factor for anything other than C-rates?

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Yes. It's correlated with battery sagging, aging cell as well as temperature

cwah said:

john61ct said:

Is resistance an important factor for anything other than C-rates?

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Yes. It's correlated with battery sagging, aging cell as well as temperature

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Sorry I wasn't more clear. I wasn't talking about comparing new vs old to judge wearing degree, for which measuring changes in IR is very useful

Just in using it resistance as a factor in evaluating / comparing different model cells for purchase when new.

At low C-rates, there is no significant warming, and voltage drop is not an issue; those are factors of concern only when getting to over, say 0.3C usage.

If the use case is low mAh, I'm thinking "maybe" the more expensive low resistance cells will last longer, but I have only seen that anecdotally and then again, in high C-rate usage scenarios.

john61ct said:

If the use case is low mAh, I'm thinking "maybe" the more expensive low resistance cells will last longer, but I have only seen that anecdotally and then again, in high C-rate usage scenarios.

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I think I got your point. Knowledge of initial cell DCIR value is not really useful for any assumption about cell cycle/calendar life. In particular many of the HP(HD) cells with low initial DCIR shows significantly worse cycle life than HE cells cycled under loads up to 1C. But there are always exceptions.

Pajda said:

I think I got your point. Knowledge of initial cell DCIR value is not really useful for any assumption about cell cycle/calendar life. In particular many of the HP(HD) cells with low initial DCIR shows significantly worse cycle life than HE cells cycled under loads up to 1C. But there are always exceptions.

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Yes, so in general would you agree that

Knowledge of initial cell DCIR value

is only useful for those buying cells where higher C-rates are important

?

Yes, it is important particularly for those who need to operate cells at high continuous C-rates.

Nicely put

“It depends on what the meaning of the word 'is' is”

And here is my small addition to discussion, :

View attachment 3
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Panasonic
NCR18650PF: NKON €2.95 / $3.26 (100-199) - IMR $3.25 (100-199)
Nominal Capacity: 2880mAh
Rated Capacity: 2680mAh
Discharge Current: 10A Maximum Continuous
Battery Chemistry: NCA - LiNiCoAlO2

Tesla uses NCA chemistry which is Nickel, Cobalt, and Aluminium (LiNiCoAlO2). They use this particular chemistry because it offers great energy density, long cycle life, and great charge performance.

"The addition of Aluminum helps NCA cells achieve the highest capacity of all li-ion chemistries. The downsides are a slight decrease in cycle life and power as compared to most other chemistries." (from DIY Lithium Batteries by Micah Toll, 2017).

PanasonicPF uses NCA chemisty and yet its rated capacity is only 2680mAh; whereas the PanasonicB cell makes use of the higher capacity of NCA chemistry with its rate capacity of 3400mAh...

Panasonic
NCR18650B: NKON €3.00 / $3.32 (100-199) - IMR $3.99 (2-199)
Nominal Capacity: 3350mAh
Rated Capacity: 3400mAh
Discharge Current: 4.87A Maximum Continuous
Battery Chemistry: NCA - LiNiCoAlO2

"The Panasonic NCR18650B was used for most all of Tesla's early electric vehicles." (from DIY Lithium Batteries by Micah Toll, 2017).

LG Chem
INR18650M36T(M36): NKON €2.99 / $3.31 (100-199) - IMR $4.25 (100-199)
Nominal Capacity: 3450mAh
Discharge Current: 5A Maximum Continuous
Battery Chemistry: INR - LiNiCoMnO2 (NCM)
INR (NCM) Batteries use a "fairly new chemistry that is still undergoing constant development" (Micah Toll quote, 2017) hybrid chemistry that adds nickel for increased capacity. The combination of both Nickel and Manganese provides not only stable chemistry but extended run times in all devices. NMC is the battery of choice for power tools, e-bikes and other electric powertrains.

“The LG M36 model 18650 battery is ideal for electric vehicles or energy storage as it has a rated life cycle of 1000 when discharged to 2.85v at a maximum of 1.8A (.5C) per the datasheet” (per IMR taken from LG M36 data sheet) … scroll to bottom of 7/13 - 4.3.4 … https://www.imrbatteries.com/content/lg_M36.pdf

My reason for listing the above is wondering if docware intended (has the fortitude) to compare 1000 charge/discharge cycles between PanasonicPF and LG M36 ? Wouldn't a fairer test have been between the PanasonicB and LG M36 being they are similar in capacity (PanasonicB: 3350mAh - 3400mAh and LG M36: 3450mAh) with the difference being the PanasonicB is LiNiCoAlO2 (NCA) chemistry and the LG M36 is LiNiCoMnO2 (NCM) chemistry.

Now that I've seen how awesome the M36 is , it makes me wonder how it would handle 5-7A.

eMark said:

My reason for listing the above is wondering if docware intended (has the fortitude) to compare 1000 charge/discharge cycles between PanasonicPF and LG M36 ? Wouldn't a fairer test have been between the PanasonicB and LG M36 being they are similar in capacity (PanasonicB: 3350mAh - 3400mAh and LG M36: 3450mAh) with the difference being the PanasonicB is LiNiCoAlO2 (NCA) chemistry and the LG M36 is LiNiCoMnO2 (NCM) chemistry.

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There is simple explanation. It is always good approach to compare cells from the same category. From my point of view there are three most popular categories in 18650 format on the market.

1. "2900 mAh" category with excellent price per kWh and discharge current up to 3C continuous and 6C peak. "Big four" offers: Samsung 29E, Panasonic PF, LG M29 and SONY NC1
2. "3500 mAh" category with the highest available energy density on the market with discharge current up to 1C continuous and up to 3C peak . "Big four" offers: Samsung 35E, Sanyo GA, LG M36(MJ1) and SONY VC7
3. "3000 mAh" category of high power cells with discharge currents more than 3C continuous and up to 10C peak. "Big four" offers: Samsung 30Q, LG HG2 and SONY VTC6

So the comparison stays: PF is compared against 29E and then GA against M36.

Original panasonic NCR18650B is not competitor for modern "3500mAh" category, because it is older generation. But its cycle life and DCIR rise is satisfactory.

Dak77 said:

Now that I've seen how awesome the M36 is , it makes me wonder how it would handle 5-7A.

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The miraculous this cell is not. At 3C continuous it wear out in just 100 cycles.