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Results of Capacity Testing 18650s for 800+ Cycles
#51
505 Cycles!!!! (Actually, I just finished Cycle 535, but I just got the time to post this now).

Here are the results:



And the degradation:


One thing that these capacity tests do not show is IR. Even though the LG cell is doing pretty well, it definitely has the highest IR. It takes the longest to charge, and it has the highest "bounce" voltage on the first test in the morning. The THLD cell, though it lost a lot of capacity, still has the tightest voltage and is the fastest to charge. I could literally do 4 tests a day if it was only the THLD cell, but the LG cell is slowing me down. It's getting to the point that I have like a half-hour window to take a picture of the third result of the day between when the THLD cell is fully charged after its third cycle and the LG cell finishes discharging its third cycle.

Androfire - I was hoping to use a Samsung, since they seem to have the highest respect, but the ones I had were too low in capacity and I didn't want it to look like I used a bad Genuine cell to inflate the performance of the Generics. So I had to use the LG - it was the best capacity 2200mAh genuine cell that I have. Ideally, I would have started with a brand new cell, but I never thought I would get to 500+ cycles, so here I am.

AcE Krystal - Well, I am fully charging and discharging these cells, so I don't have any hard data on limiting voltage ranges to prolong life. That kind of test takes a lot of time and sensitive equipment, neither of which I have.

eas - Actually, I do believe self-discharge rate and cycle-age are correlated. When I look at my genuine cells, the cells that self discharge more usually have less capacity. There are of course damaged cells that have great capacity and self-discharge a lot, but in general, cells that are near full capacity will still be at 4.18V after 6 months, while the ones that only have 70% will be around 4.12V after 6 months. Also, don't get me wrong, there is still a lot of Chinese junk out there. But it seems that even in 2011 when these cells were produced, some Chinese manufacturers were already producing decent quality cells. I guess it's like Honda/Toyota in the 80s or Hyundai in the 2000s got a bad wrap for producing junk, and it took some time until those cars became mainstream. I was also considering switching slots every cycle and rotating the cells randomly, but didn't for 2 reasons - (1) I hand wrote capacities and later transferred to a computer; it was easier to keep track of the cells and their capacities every 25 cycles than every cycle; and (2) I didn't rotate the cells in order to keep the cell's label on every picture I took. With the personality I have, I don't really trust anyone I don't know, and I always am second guessing their motivation for giving me information. Usually if someone is trying to sell me something, I assume the opposite of what they say must be true. Anyway, by keeping the cells label-up for the pictures I took of every cycle, I wouldn't have someone telling me the test is fake because I was switching out cells for new ones all the time to inflate the generic cell's results. Paranoid? Maybe. I guess you could photoshop results, too. Anything can be photoshopped, but now that would be paranoid. Yes, part of the jaggedness would be temperature variations. But also, internal resistance, the Opus' margin of error, and how long the cell was charged from the previous cycle all play a part. Again, if I were publishing a scientific paper on this, or selling these cells to a large buyer, you bet I would be doing all you mentioned, as well as Thunderheart, Oz18650, and the rest. All very good suggestions on making this test 100% accurate and reliable. I was just going for good enough for our community while minimizing the shortcomings. People are free to treat my test as inaccurate, and I welcome literally anyone else to do this test over with better equipment and publish the results for everyone free of charge.

Oz18650 - This test was performed by me in my home. The coldest it would get in my home would be 70*F in winter and in the summer maybe 82*F in the afternoon. But that would be minimum and maximum. Most of the time my home is between 74*F and 76*F. I also never test overnight for obvious reasons, not that it would matter much indoors. I agree that temperature matters a lot - look at my post about Cycle 35 where I just ran a 120mm computer fan over the cells. There was a 3-4% decrease in capacities for that cycle.
Formerly known as Dallski
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#52
605 cycle update: Degradation on the CJ and THLD cells looks like it is accelerating. The LG and ASO cells are still degrading fairly linearly. The test is getting a bit slower, I'm doing about 2 cycles a day instead of the usual 3 cycles. I'm going to continue this test, but I'm starting to get a bit fatigued by it. I have been doing this since January! 





Formerly known as Dallski
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#53
(09-09-2019, 04:20 AM)Generic Wrote: 605 cycle update: Degradation on the CJ and THLD cells looks like it is accelerating. The LG and ASO cells are still degrading fairly linearly. The test is getting a bit slower, I'm doing about 2 cycles a day instead of the usual 3 cycles. I'm going to continue this test, but I'm starting to get a bit fatigued by it. I have been doing this since January! 

...

Fascinating information. I imagine if you are going to test a cell to its final end, it's going to take way too long.

It would be interesting to know if these cells have begun to self discharge yet.
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#54
Based on the curves in the chart, I'm expecting the CJ and THLD to get to 0 capacity around 800 cycles, maybe? Self-discharge would mean I would have to stop testing for a week or so, and I can guarantee you that I won't continue the test if I do that, so I'll hold off for now.

That being said, I have noticed that the initial voltage drop on the LG and ASO cells has been rather high, like the cell dropping to 4.00V after just a minute of discharge from 4.2V. The CJ and THLD, despite their capacity loss, only drop to around 4.12V in the same time.
Formerly known as Dallski
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#55
(09-09-2019, 04:56 AM)Generic Wrote: Based on the curves in the chart, I'm expecting the CJ and THLD to get to 0 capacity around 800 cycles, maybe? Self-discharge would mean I would have to stop testing for a week or so, and I can guarantee you that I won't continue the test if I do that, so I'll hold off for now.

That being said, I have noticed that the initial voltage drop on the LG and ASO cells has been rather high, like the cell dropping to 4.00V after just a minute of discharge from 4.2V. The CJ and THLD, despite their capacity loss, only drop to around 4.12V in the same time.

That is really quite intriguing. It would be great if you had an iCharger or similar, to get a graph of the discharge voltage. Perhaps even set up a camera, to take photos every 5 minutes. If you uploaded a zip of the images, I would type them out so you could graph them. Shouldn't take me too long.
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#56
It is interesting to me that of the four cells 2 are behaving similarly to each other while the other 2 are similar to each other.
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#57
I'm intrigued about the performance above 80% (1760 mAh). Most of us out there are using some kind of combination of capacity, % capacity, resting voltage, and IR to determine that a cell will continue to perform as tested for an acceptably long amount of time after harvesting. In the case of the two cells that are rapidly dropping off, if I were to harvest them when they were testing at 2000mAh they would look okay in terms of capacity and % capacity, do you think they would pass resting voltage and IR checks too?

Are the standard tests enough to catch cells that are about to nosedive?
Mobilis in Mobili
 
Cell count as of 10/10/2019
234 Cells >2000mAh, >80% Rem. Cap., 14 day resting voltage >4.12V
191 Cells of Everything Else
68 In progress
 
Aiming for 8 cells tested a day
More info on my Google Drive
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#58
Oz - I am starting to think that the CJ and THLD are both made by the same manufacturer, just different labels. It's rumored on this forum and on other forums that ASO are rewrapped rejected Samsungs, which could explain why it is closely tracking the LG cell.

Nemo - The standard tests are standard because they are fairly quick and reasonably accurate. But they won't catch everything. Even though I rebranded myself "Generic," I did harvest about 1,300 genuine cells before I had the opportunity to get around 10,000 new-old-stock generic cells for pretty cheap. I just went through a 5 month process of retesting my 1300 genuine cells (and putting them into storage voltage), and there were 42 cells that tested well initially (between 80 and 95% of original capacity), did not self discharge, but retested at 30-40% capacity after sitting at full charge for anywhere between 8 months and 1 year. And these were not cells that were recovered from 0V or anything, just very normal cells. Apparently, this is not new, I read about this phenomenon in a Battery University article, but it is a risk that you take. I wish I had taken IR measurements along the way, but I never invested in an IR tester, so we will never know. All I know is that manufactures usually quote how many cycles you get above 80%, so I'm guessing most cells will nosedive some short time after 80%.
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Formerly known as Dallski
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#59
I do not know, but it may be that quoting 80% is a business decision, rather than for technical reasons.
Once something battery powered losses more than 20% of its runtime, it is definitely not running "like new".
The next number down (75%) might be too low for cell buyers and the next number up (85%) might be too high for the cell makers, so they settled on 80%?
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#60
Wow, you did all these cycles manually? If you're interested in continuing this sort of testing I could send you an 18650 cycle tester I've been working on (would be an older version of which I have several), details are here: http://rev0.net/index.php?title=CCR It sure seems easier than manually restarting a cycle on these cells and taking down the data.
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