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Results of Capacity Testing 18650s for 1,400+ Cycles
#91
The graphs are very interesting.
It's great that the good cells are still at 80% capacity after 1000 full cycles.
Shows good promise for those building powerwalls which will be less stressful on the cells.
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#92
Such a test would be extremely interesting to be repeated after 1 year using the same cells.
That would allow us to see how storage affects them.
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#93
I do not recall seeing, but I would imagine there are plenty of folks who have cells in storage that could retest after 1 or even 1.5 years. Finding 2 years may be a stretch.

Is there a Benifit to testing using the Same cells as this thread

Given the high number of cells I have in storage it would be interesting to see if there is any long term impact
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#94
I have cells I have stored at various states of charge, just by chance (if I noticed the discharge part was done I pulled it off the charger), so I'll be retesting those in some time to see how that affects capacity.
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#95
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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#96
I have done storage test and i would say that normal storage is less than 6% degradation per year. As specs from manufactures and other tests.
I had like 2% degradation per year in average on the cells i tested.
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#97
2x Samsung 22-F, 2012. Never used, only stored at full charge.

Capacity Opus-tested in 2018: 2000mAh. That is a 10% drop in 6 years.
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#98
Fullt charged dropps more. Manufacturer claim as much as 6% per year.

Overmind note that Opus shows Up to 10% above. So your test could be more like 15% drop over 6years
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#99
Good job!! It's very interesting data. 
I am doing similar tests with Liitokala NCR18650B cells (from aliexpress). In my case, I have built a tester that performs automatic charge and discharge cycles with Arduino. For the charge I use a TP4056 (1A), and for the discharge a resistance that I have made (2A approx.). Every 30 cycles I perform a test with the OPUS to measure the capacity of the cell. For now I have 180 cycles. I leave you a graph with the result:

[Image: grafica_degradacion_NCR18650B-1.jpg]
I leave you a link where I have more details of the test: https://electrotinker.com/en/analysis/degradation-ncr18650b-liitokala/

Thanks!
P.S. Sorry for my English, it is not my native language  Undecided
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Update time! Sorry I never got around to posting at 1100 cycles, I had everything ready, but didn't get a chance to log in here and post it. Here is the degradation chart, at least:



So, I have made it past 1200 cycles! Right at Cycle 1175, the Opus fan finally gave up (it was moving, just not enough to remove much heat), and you can clearly see a spike in the results. I have several replacement fans on hand, so it didn't cost me any time. Otherwise, it's been pretty uneventful. The THLD cell is sitting at 4.13V and the CJ cell is sitting at 4.14V after almost 4 months, so they are not self-dischargers, despite being end of life. I'm not going to be checking those voltages anymore. The ASO and LG cell are continuing their very slow, almost linear, decline. On the one hand, I'm wishing they would just die already so I can end this test and not feel guilty about ending it early, but on the other hand, I'm rooting for these cells to keep going because the results of this test are so much bigger than the fate of 2 random cells. Anyway, here's where we are at:





And the degradation:



@Diegobg - Nice work! The 2 Amp discharge is putting more stress on the cells, so it looks like they are degrading faster, about 9% loss in capacity, right? Are the cells heating up at all?
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Check out my long-term capacity test of 18650s: https://secondlifestorage.com/showthread.php?tid=6868
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