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"Generic" Cells - Are they any good?
#21
@Wolf Thanks, I'll 1st check if e-bay UK has any offers since I do have friends in the UK that come back home from time to time.
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#22
Ok, it is time to release the next set of results. Finally seeing some degradation! Here's the chart: 
 
And a little closer look:
 

You can see a definite trend. Just going to repeat a few things if you don't want to read from the beginning. Since I am rotating cells every 25 cycles, and the right two slots get warmer than the left two slots, when a cell is on the right side, it benefits from heat adding capacity, and when it goes from slot 4 to slot 1, the capacity takes a hit. Also, the missing data for the THLD cell in Cycle 129 is from the slot being sticky and going null on the recharge. I didn't get a reading, but when I took the cell out and put it back in, it was at 3.29V, so I know it had gone through a full cycle. Also, because I am rotating every 25 cycles, I wait until 5 cycles into the next rotation to compare to the first 5 cycles, so that there is no slot selection effect. 

With that being said, here is the degradation observed over 205 cycles. The first row is the average of Cycles 1-5 and the second row is the average of Cycles 201-205 for each cell. The third row shows the percentage of degradation of each cell.

 

Please keep in mind that the LG cell did not start out this test as a new cell, and already had a number of cycles or cycle equivalents on it before the test got started. The other cells are 8 year old cells that were never used. And as most of us know, degradation is not linear, it accelerates. 

Anyway, I'm continuing this test. I just finished Cycle 213. I would have posted this earlier, but I didn't really have a chance.
stevelectric likes this post
Formerly known as Dallski
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#23
Thanks for doing this testing and sharing with us!
It is very interesting!
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#24
Thanks for the positive feedback! If I help even one person, it will all be worth it.
Formerly known as Dallski
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#25
@Dallski,

Nice work on graphing those results. I had similar results with the "do green sony cells suck" experiment although I only did 11 cycles.
I did find out one thing though. If I let the cell rest for a day or so between cycles the results where much more even and consistent.
It's also interesting that every so often the cells jump back up as if they want to do better and then go back down over the next couple of tests.
It would be interesting to see if you let the cells rest a day or two and then test them again if they jump back up like some of my Sony's did. 

It's only 11 cycles but it does show the downward trend of the 56 cells. Some of them where pretty flat line though pretty even all across the 11 cycles. The big A pillar is me playing with the SKYRC and pretty much ruining 4 cells with an 20mA cutoff charge but boy did they have a great discharge result but only once. Smile
Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
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#26
Thanks Wolf! You give a lot of effort testing cells and chargers, so it means a lot coming from you since you're kinda in the same boat as me. I wish I could test these at 200mA, only test from 80% to 20%, and give them a break in between and see how much life they could give. But by the time the test was done, lithium would be the new NiCd LOL. I'm trying to put the most stress on these cells that the Opus can give them within reason, of course. Im getting roughly 3 cycles done a day at 1A charge/discharge, and 1 break between night and morning. In real life, these will only do 80/20 max, maybe 200mA on average, and only go through one charge/discharge cycle a day. So whatever results I get, they are kind of a worst case scenario, really. And they are pretty darn good so far. If you get double cycle life by just charging to 4.1 instead of 4.2, imagine what you get if you only go between 3.4 and 3.9! Anyway, there might be a time where I give the cells a break for a couple days, but I dont see it coming up. Maybe when the cells degrade a bit more. Lastly, I know people say there is very little capacity between 4.1 and 4.2V, but as you observed with a 20mA cutoff, you can pack a lot of charge into an older cell between 4.1 and 4.2!
Formerly known as Dallski
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#27
(04-16-2019, 03:13 AM)Dallski Wrote: With that being said, here is the degradation observed over 205 cycles. The first row is the average of Cycles 1-5 and the second row is the average of Cycles 201-205 for each cell. The third row shows the percentage of degradation of each cell.

 

@Dalslski 

Here is another look at the numbers with a little bit different formula. It calculates the percentage of capacity lost over the ~200 cycles and its not that bad. The worst one is the LG and as you said was not a new cell anyway.

Wolf

If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
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#28
If you have the results for tests 101-105, it would be interesting to me to be able to compare the rate of degradation over time.
Ie. Is it a straight line from test 1-5 to tests 201-205, going through tests 101-105?
OR does the rate of capacity drop increase (or decrease) over time?
Tests at 300, 400 and 500 cycles would really show how this progresses, but it is a lot to ask.
I think this would help people to decide how important SOH (based on current capacity compared to original capacit) is when deciding on using cells.
Some people only use cells with at least 80% of original capacity, while others use a different % of original capacity, while others use "must have at least 2000mah capacity", while others use "must have at least 1200mah capacity".
All of these approaches seem to work, however I don't think there is much info on " How will the resulting packs last over time".
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#29
@Wolf: Technically, you are correct - degradation should be the number you posted, while the number I posted is....something else. I'm just so used to the other way around I didn't think about it. From your calculations, the LG cell lost 5.5% capacity over 200 cycles. According to its data sheet, it is a 300 cycle rated cell, meaning it should have about 80% of its original capacity after 300 cycles. It seems to be outperforming the datasheet numbers for some reason.

@ Oz18650, Yes, check the Original Post, I have been updating that incrementally so that anyone who is new to this forum can get the whole test without sifting through each page. It's fairly straight-line right now, but with so little degradation, it's hard to say. I'm pretty sure that degradation does accelerate with cycles based on the testing I've done with my genuine cells, but it hasn't shown itself in this test, yet.
Formerly known as Dallski
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#30
Has anyone ever found any datasheets from the manufactures 'generic' cells? Specifically the ASO and SZN batteries, as I do have a reasonable quantity of them.

It looks like they hold up reasonably well, and I do intend to use them. Many came from cheap laptop batteries with BMS problems, so the cells have tested quite well.
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