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Does internal resistance matter?
#31
(01-13-2019, 08:33 PM)daromer Wrote: That was only 1 Link. You can find papers testing 10 000 cells to. They Will all show the same result. The xray is not needed but its a way to show what happens.

OK i will keep looking. 
Also if anyone else out there stumbles across such a study please let me know.
I don't want to waste anyone's time especially mine if all this has been already done and we just haven't found it yet.
Such a waste of time for me but I will look on the bright side at least I learn a lot. Smile
My hope is to have a go, no go, and a  maybe IR reading for the most common cells that we find. 
If anyone is interested in my results please let me know and I will continue otherwise I will just stop and do it myself. Sad

Thank you.

Wolf
100kwh-hunter likes this post
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 6/10/2019
Total Number of Cells                          5940
Cells  >80% of Capacity                      4334
Cells <80% of Capacity                       1605
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2800 +236
For Info Google Drive
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#32
I dont understand how you dont see the info in the documents out There. There are plenty of tests by degradation done. Just. Just the formulas or take their charts. Or are they to generic for ur liking?
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#33
I do see the documents and have read a bunch of them and yes they all analyze the cells in hundreds of different ways.
That is all fine and good and yes it proves that IR rapidly increases during the first trimester of the cells life, slows down during the second trimester of the cells life and then rapidly increases again during the last trimester of the cells life.
So what does that tell us? Buy new cells right? Forget about harvesting these cells as you are wasting your time.
I think not.
As I said before this is NOT a study of what happens to a cell during its life cycle as you constantly refer to the "STUDIES" that have been done on such matters. It is a study to determine a baseline for us users to be able to tell if a cell has some usable life in it and to quickly determine if a cell is worth putting the time and energy into it. That's all. Nothing more nothing less. I do not see what is so difficult in understanding that.

Example
Again all IR testing is done with a YR1030 4 wire Kelvin IR tester.

ICR18650-22F  below 60mΩ IR very good candidate for testing. 60mΩ to 75mΩ marginal and over 75mΩ more than likely lower capacity.
CGR18650CG   below 55mΩ IR very good candidate for testing. 55mΩ to 65mΩ marginal and over 65mΩ more than likely lower capacity.
LGABB41865    below 80mΩ IR very good candidate for testing. 80mΩ and up rapid fall of and much lower capacity.
UR18650FM     below 55mΩ IR very good candidate for testing. 55mΩ to 65mΩ marginal and over 65mΩ more than likely lower capacity.


There is some IR deviation with voltage of the cells but so far the variations have been negligible somewhere around -3% to +3% high average

I can go on and on but the database is not complete yet and these are preliminary results with only ~800 cells of different manufacturers tested.

Now with this information wouldn't that make it easier to harvest cells quicker?  The person with 30 testers may not think so but I guarantee you the guys with 1 or 2 testers would really appreciate this data and information. I certainly don't see that published anywhere.

If you don't understand that logic I will throw an 18650 over the pond at you. But I will measure the IR first to make sure it not a good one. Tongue

Wolf
100kwh-hunter likes this post
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 6/10/2019
Total Number of Cells                          5940
Cells  >80% of Capacity                      4334
Cells <80% of Capacity                       1605
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2800 +236
For Info Google Drive
Not your average Wolf       
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#34
You need to look at the charts showing the ir compared to capacity compared to cycles. They exist Wink i think you look to much att the fact that it have been tested in controlled environment and on new cells and that they state buy new or see how much they degrade. Turn it around and look at what their Numbers are in the end of the cycles instead Wink

You dont have to listen to me and you can test and i admire you do because a DIY test Will rank higher than a pushished study do. You are for instance proof of that Smile
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#35
Yes the cycles do make a difference don't they. Smile
Further study is needed. In the meantime though Im almost half way there for my 14s 200p bank.

I'm kind of hesitant to retest the first batch of ~700 cells that I already have boxed and waiting.
I may do that anyway though just to build the database and also have a record of each cell.
Just thinking out loud yea I think I will sort them by make and model and retest, as a bunch where tested with the Zanflairs and you know what I think about those tester. Smile

They are basically serving me as chargers along with the XTAR and Nitecore.

Later

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 6/10/2019
Total Number of Cells                          5940
Cells  >80% of Capacity                      4334
Cells <80% of Capacity                       1605
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2800 +236
For Info Google Drive
Not your average Wolf       
            Cool



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#36
I am retesting and paying attention to IntR and brand. I have ditched so many. I opened 3 camera batteries yesterday (4s4p) and tested intR on a couple and was able to determine to chuck the whole pack. I can safely use moli under 95. Sanyo under 70. All the pink samsungs with batts the same age pull up really well and seem to be under 65. So they are REALLY different.
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#37
(01-15-2019, 12:39 AM)camthecam Wrote: I am retesting and paying attention to IntR and brand. I have ditched so many. I opened 3 camera batteries yesterday (4s4p) and tested intR on a couple and was able to determine to chuck the whole pack. I can safely use moli under 95. Sanyo under 70. All the pink samsungs with batts the same age pull up really well and seem to be under 65. So they are REALLY different.

Camthecam,
Isn't it nice to know when you put cells into the testers that you will more than likely have a good result. Big Grin

I just went through 18 ICR18650-30B cells all with an IR of +70 mΩ I know what the results will be but for the sake of the dataset I will process these.


Also checked 31 ICR18650-28A with less than 60mΩ and I know these will make me smile.  Smile Smile


I have so many examples in my spreadsheet now I just about know what's going to happen. But for the sake of data collection and having a huge dataset to analyse I am still testing all cells except of course the 0Vs and super high IR as in .236Ω then we should be able to come to a good conclusion and be able to build a chart for us DIYers with the most common cells as to what the cutoff should be.


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 6/10/2019
Total Number of Cells                          5940
Cells  >80% of Capacity                      4334
Cells <80% of Capacity                       1605
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2800 +236
For Info Google Drive
Not your average Wolf       
            Cool



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#38
Hi Wolf

One thing I have been wondering is how this new method compares to what I originally learned from this site which is to put the cell under load and watch the voltage take a quick dive and stabilize.

If voltage dropped into the 3.7 v range it was no good. Sure enough if you finished capacity testing you verified this

I understand this is time consuming to charge, but at end is there any difference in cell being discarded by either process

Hope this is clear.
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#39
I haven't seen anything close to what you guys are stating!
I have 3000+ cells testing with 3100's and I don't have anything below 70's
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#40
Chiptosser,

Yea neither have I on the 3100 but you obviously know that by reading this thread that we are measuring true IR with a 4 wire kelvin tester.
Right? 
Also the OPUS instruction manual has some info on IR readings. I have highlighted it for you.


I mean I have published the IR results on the sheets with the YR1030 tester that I use and along with the OPUS and LiitoKala.
Opus IR readings plainly stated.


I hope that this clears up the confusion.

Wolf

(01-16-2019, 12:09 AM)Chablis_m Wrote: Hi Wolf

One thing I have been wondering is how this new method compares to what I originally learned from this site which is to put the cell under load and watch the voltage take a quick dive and stabilize.

If voltage dropped into the 3.7 v range it was no good.  Sure enough if you finished capacity testing you verified this

I understand this is time consuming to charge, but at end is there any difference in cell being discarded by either process

Hope this is clear.
Hm yes I know of that concept and have not devoted that much time to it. (Gee I wonder why? Too much time recording IR and cell capacity in the sheet besides finding time to break some packs appart)  Smile  It would be interesting to see if there is a correlation between IR and the V drop.  I'm kinda sure there is. I will put it on my list of things to check out as I'm working my way toward at least 2800 cells for my wall. But the purpose of my exercise is to avoid charging cells that will not perform.

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 6/10/2019
Total Number of Cells                          5940
Cells  >80% of Capacity                      4334
Cells <80% of Capacity                       1605
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2800 +236
For Info Google Drive
Not your average Wolf       
            Cool



Reply


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