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18650 sanyo cells get's very hot
#11
(05-02-2019, 06:18 PM)Wolf Wrote:
(05-02-2019, 05:59 PM)Cherry67 Wrote:
(05-02-2019, 03:23 PM)Wolf Wrote: ( I probably should change my user title from Senior Member to a custom one "IR King") :D

And what am i ?? :D

Oh you are the IR god :D

Wolf

(05-02-2019, 05:51 PM)drbacke Wrote: I use the same IR tester, but IR was never a good predictor for heaters in my database. 
I have a lot of Sanyo cells with very low IR (even low in the same bunch) and there was no correlation between heaters and ir.
Only for self discharging the IR seems to be a low quality predictor. In combination with the relative capacity the self discharging rate is predictable. But also with very big deviation and only the self discharging rate in 14-30d. 
If i would have more data i would be able to programm a statistcal predictor for self discharging by given relative capacity and pre IR.

@drbacke

It may not necessarily be the best predictor of heaters but it is a pretty good start. As you can see by my stipulations to the challenge I did leave myself a 5 cell per 100 leeway. Which is a 95% success rate any way you look at it. Plus the added bonus of my IR cutoff chart is that these cells will produce at least 80% capacity. Now there is such a thing on the Sanyos as a too low of an IR and maybe I should have mentioned that. The chemistry in question really is usually ICR low drain and anything <30mΩ on that type of battery is to be questioned. I have had some UR18650FM cells with an IR of 23mΩ to 26mΩ. Those normally run in the >45mΩ  range, that were almost instant heaters. 

As far as the SD's are concerned IR is absolutely a great indicator the cell will degrade in the 14 to 30 days to an unacceptable V level.
But in the final analysis IR is really important in the determination if a cell is healthy or not. Unfortunately with the many different chemistries out there (slight difference as they may be) between different manufactures and different part numbers the IR measurement fluctuate widely
between cells. But one thing I can tell you for sure any 18650 cell with a reading of 100mΩ or more is not worth messing with. 

You are always welcome to check my data out as it is on my google drive.

Wolf

I know your results and the are very interesting. But results must be reproducable by an identical setup, which i have. Otherwise the results must be checked by a third Party to be sure. But i didnt see your max ir rates for the sanyos. So maybe this will change my results. I will tell you tomorrow and I hope you are right, this would help a lot ;)  
But the correlation between the SD and the IR is not very high i think, even not in your DB. Also i cant see the start voltage after first charge (not every charger reaches 4.2V) in your DB, so the voltage drop is not known. But maybe i just have the wrong DB, if so please tell me. But i will calculate the correlation factor  with 4.2V assumption. So tomorrow I will do some math and present you the results. 
Maybe i will have time to build some high order model for multivariate statistics. This could help to get reliable prediction results.
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#12
Doc, i can second Wolfs opinion, on a much smaller database on my side,  for the correlation of SD to IR is, that there is next to none.

There is as well hardly a valid physical explanation why it could/should be correlated.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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#13
(05-03-2019, 08:51 AM)Cherry67 Wrote: Doc, i can seccond Wolfs opinion, on a much smaller database on my side,  for the correlation of SD to IR is, that there is next to none.

There is as well hardly a valid physical explanation why it could/should be correlated.

This picture is made with wolfs database, it's IR over Self Discharge Rate in30d. There is no correlation at all and even with all these different cell types there should be one:


The following picture is Relative Capacity (or capacity left in %) over self discharge Rate, you can see a small correlation:




If I made any mistake, please let me know. But these diagrams support my statement (with wolfs data).

This picture shows the relative capacity over IR and of course you see a greater correlation. 
 

IR / Left Capacity = high correlation
IR / Self Discharge = low correlation
Left Capacity / SD = high correlation

This brings me to the result, that IR give's you a picture of how "hard" a cell's life was and left capacity gives you a good picture of the internal ageing effects of the cells. So the combination of both is quite sensefull.
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#14
Well I am glad someone is using the database I created to get some interesting results.
Good work. Now just to say a couple of things.

1 I only created this data base to try and figure out if there is any correlation with IR and percent of capacity.
As we can plainly see there is and it has proven to be very effective to weed out poor cells in the beginning.

So for number 1 mission accomplished and the creation of the IR by part# sheet was created.
This is a work in progress and will be added to and edited as is necessary.
If you adhere to these mΩ numbers by cell manufacturer and part number your chances of getting an 80% plus of original capacity result are greatly improved.

2 The amount of data has also shown SD cells and some heaters. As my harvesting has evolved I have not come across very many heaters as anything over 100mΩ doesn't even get tested anymore and I am rapidly going to a 90mΩ cutoff.

The SDs on the other hand are still a thorn in our sides as there is no serious correlation so we just check them after 30 days what can I say.
I guess I won't get my doctorate degree on SDs

Wolf

(05-03-2019, 10:38 AM)drbacke Wrote: This brings me to the result, that IR give's you a picture of how "hard" a cell's life was and left capacity gives you a good picture of the internal ageing effects of the cells. So the combination of both is quite sensefull.

I find that if filter just by cell part number and sort the IR by highest to lowest ............Lets take the UR18650FM and graph the mΩ and %Capacity correlation we see a definite mΩ to capacity correlation. We get this result of capacity within an IR range.



Wolf
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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 5/23/2019
Total Number of Cells                          5354
Cells  >80% of Capacity                      3801
Cells <80% of Capacity                       1553
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2645 (155) to go
For Info Google Drive
Not your average Wolf       
            Cool



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#15
(05-03-2019, 11:16 AM)Wolf Wrote: Well I am glad someone is using the database I created to get some interesting results.
Good work. Now just to say a couple of things.

1 I only created this data base to try and figure out if there is any correlation with IR and percent of capacity.
As we can plainly see there is and it has proven to be very effective to weed out poor cells in the beginning.

So for number 1 mission accomplished and the creation of the IR by part# sheet was created.
This is a work in progress and will be added to and edited as is necessary.
If you adhere to these mΩ numbers by cell manufacturer and part number your chances of getting an 80% plus of original capacity result are greatly improved.

2 The amount of data has also shown SD cells and some heaters. As my harvesting has evolved I have not come across very many heaters as anything over 100mΩ doesn't even get tested anymore and I am rapidly going to a 90mΩ cutoff.

The SDs on the other hand are still a thorn in our sides as there is no serious correlation so we just check them after 30 days what can I say.
I guess I won't get my doctorate degree on SDs

Wolf

I enjoy working with your database very much and it helps me to understand things better or at least to question many of my own views about the harvesting process. Thanks a lot for that, your work allows me to make my harvesting process safer and more efficient in the future or at least to understand it more. I hope it didn't come across as criticism. It's just my way of understanding things. 
At the moment some things still seem unclear to me, the correlations are very strange and partly even contradictory. 
I will try to research these things and then share the results with you. I think there are different kinds of cell degradation which leads to different kinds of IR/SD/Capacity values.

---------
This picture is very interesting. I agree, this seems to be highly correlated. But there is also a very wide range of deviation, maybe we can understand how this all depends.
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#16
(05-03-2019, 11:30 AM)drbacke Wrote: I enjoy working with your database very much and it helps me to understand things better or at least to question many of my own views about the harvesting process. Thanks a lot for that, your work allows me to make my harvesting process safer and more efficient in the future or at least to understand it more. I hope it didn't come across as criticism. It's just my way of understanding things. 
At the moment some things still seem unclear to me, the correlations are very strange and partly even contradictory. 
I will try to research these things and then share the results with you. I think there are different kinds of cell degradation which leads to different kinds of IR/SD/Capacity values.

Well I'm glad that several people on this board have found this data to be useful. It have been doing this for ~5 months now and are now seeing the results of that labor. Criticism I welcome it. I think its healthy after all we all are trying to find some answers.

Several things I want you to take into account when viewing this data.

1. In the beginning I was just taking random cells and recording them as you can see by the small baches.
2. There was no thought on what IR to eliminate from the tests and Voltage was also no consideration.
3. When it became apparent that IR was an influence and that precharging was a faster way of building the database that was introduced as you can see by the pretest measured Voltages.
4. High IR cells where again introduced into the data to give a balance and find the cutoffs.
5. Some cells where pulled from the testers before they were completely recharged after the test and may have indicated a SD in error.( I have long since changed that and let all cells finish charging). If caught on the SD check and because the IR readings  indicated a good cell they were recharged and set aside for another 30 day waiting test. After that they will be entered.
6. Post recharge voltage was not checked except the occasional spot check and the results usually where in the 4.16V to 4.19V range.
7. My SD cutoff is set to 4.13V with conditional formatting. Compared to many who use 4.05V as their criteria mine is relatively higher.
8. from cell #4500 on I started the IR experiment. (Missing some cells there in the first 100? Not sure what happened. I'll see if I can find them in a previous version)(Found and fixed) As you can see the capacity results are very good from there on. There are some low numbers in there but that again was to find the cutoff on certain part number cells.
9. I now do not precharge any cells >2.0V. If the IR is acceptable they go straight to the charger/tester. If the cell is <2.0V and the IR is acceptable they get precharged with CC/CV  4.2V 50mA.

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 5/23/2019
Total Number of Cells                          5354
Cells  >80% of Capacity                      3801
Cells <80% of Capacity                       1553
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2645 (155) to go
For Info Google Drive
Not your average Wolf       
            Cool



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#17
(05-02-2019, 06:18 PM)Wolf Wrote:
(05-02-2019, 05:59 PM)Cherry67 Wrote:
(05-02-2019, 03:23 PM)Wolf Wrote: ( I probably should change my user title from Senior Member to a custom one "IR King") Big Grin

And what am i ?? Big Grin

Oh you are the IR god Big Grin

Wolf

Just call me Majesty, that fits Big Grin Big Grin
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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#18
(05-03-2019, 12:23 PM)Cherry67 Wrote: Just call me Majesty, that fits Big Grin Big Grin

OK your Majesty, Kaiser and such.

Wolf Smile
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 5/23/2019
Total Number of Cells                          5354
Cells  >80% of Capacity                      3801
Cells <80% of Capacity                       1553
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2645 (155) to go
For Info Google Drive
Not your average Wolf       
            Cool



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