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Harvested cells analysis.
#1
Alright I have recorded 2711 cells in my spreadsheet and on my way to 3000 plus. Where it will end no one knows. It may not end at all although once I get my 14s200p wall built it will probably slow down some. Big Grin

So I have been having fun with excel and have built a "Cell Calculator" that pulls data from my main sheet and filters it according to mAh per cell Then refilters to >80% capacity.
In other words enter the minimum mAh per cell required in your pack and it will spit out the results of how many cells that have been tested that have that result or greater. It also calculates the average mAhs of all the cells and then can multiply that by the number of p which will give you the Ah of that pack. You can adjust the max cell V, # of strings and then calculates the kWh of the whole pack.
So I did some scenarios with 2000mAh to 2300mAh entered.
I may change my mind now and go with as low as 2100mAh cells. First of I have a lot of 2200mAh rated cells that are testing at >80% of capacity mostly much better 90%+ but that is in the cutoff area of <2200mAh.
I have also added the IR calculations as a side benefit for those that are interested.
I can say this much as my IR investigation continues, I can just about guess what the capacity of a given cell is going to be just by the initial IR measurement alone. But I digress.
Here are the results of 2000mAh to 2300mAh pack calculations. Interesting to see that between the minimum per cell from 2000mAh to 2300mAh the total increase is only 1.73kWh.
So with this information would you reduce your cell requirements to 2000mAh or as I possibly plan to 2100mAh or would you hold out for the jackpot of all at least 2200mAh? I am itching to get started on my cell packs but I also want the best possible cells. So the dilemma continues.


Wolf
djmrush, Church1182, 100kwh-hunter And 1 others like 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 3/23/2019
Total Number of Cells           3743
Cells  >80% of Capacity        2445
Cells <80% of Capacity         1265
Cells ≥2200mAh & ≥ 80%     1709
Google Drive for info https://drive.google.com/drive/folders/1...sp=sharing
Not your average Wolf       
            Cool



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#2
I would hold out for 2200mAh. If you have the patience to take apart and test 2711 cells, then you have the patience to wait to build a minimum 2200mAh wall!
Church1182 likes this post
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#3
(02-27-2019, 07:58 PM)Dallski Wrote: I would hold out for 2200mAh. If you have the patience to take apart and test 2711 cells, then you have the patience to wait to build a minimum 2200mAh wall!
He He yes patience I know. I do have that so no worries.
This question just kind of came up in my mind as I was testing lots and lots of Samsung ICR18650-22* series cells. I went through my sheet and found that a high majority of them are in the high 80s and up in capacity percentage. I still have a lot more to test in packs I haven't even broken apart yet. So these cells are relatively very good if not excellent and probably have a lot of life left. Even just dropping to 2150mAh I pick up 147 cells and at 2100mAh I pick up a whopping 285 cells. Also I only loose .29kWh and .57kWh respectively.
Do you think that percent of capacity remaining trumps tested mAh?
I mean I won't be using cells below 80% of capacity anyway so cells with high 80% and up look very attractive still limiting them to at least 2100mAh.
I certainly can use these cells in some other project.
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 3/23/2019
Total Number of Cells           3743
Cells  >80% of Capacity        2445
Cells <80% of Capacity         1265
Cells ≥2200mAh & ≥ 80%     1709
Google Drive for info https://drive.google.com/drive/folders/1...sp=sharing
Not your average Wolf       
            Cool



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#4
I would have to agree with Dallski. You've come this far, might as well see it through.

Love the spreadsheets.

Edit: Although if you are using cells that still have that much life, I would lean towards remaining life over actual capacity. Barely.
Dallski likes this post
James 1:19-20

Not all those who wander are lost - J. R. R. Tolkien
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#5
(02-27-2019, 09:18 PM)Church1182 Wrote: I would have to agree with Dallski. You've come this far, might as well see it through.

Love the spreadsheets.

Edit: Although if you are using cells that still have that much life, I would lean towards remaining life over actual capacity. Barely.
LOL yes I know (barely) it is a dilemma isn't it

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 3/23/2019
Total Number of Cells           3743
Cells  >80% of Capacity        2445
Cells <80% of Capacity         1265
Cells ≥2200mAh & ≥ 80%     1709
Google Drive for info https://drive.google.com/drive/folders/1...sp=sharing
Not your average Wolf       
            Cool



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#6
Are you taking into account tester correction factors? I know you have tested all your testers for accuracy. I'm saying that your 2200mAh cells could be 2000mAh in real life depending on the tester, as you know.

Also, if you limit yourself to 2200mah+ you probably won't be using those Samsung 22Fs or any other cells that had an initial capacity of 2200mAh or less. Those tend to be either older cells, or budget cells that might only be rated for 300 cycles, as I just recently discovered.

Of course, I'm not saying those other cells are useless, I'm just saying if you have a steady supply of cells, hold out for a more energy-dense powerwall. You can always use those sub-2200mah 80%+ cells in a parallel pack.

As for capacity vs remaining life, I would have said that remaining life would be more important. But I'm starting to think that the cells would just equalize over time.
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#7
(02-28-2019, 06:47 AM)Dallski Wrote: Are you taking into account tester correction factors? I know you have tested all your testers for accuracy. I'm saying that your 2200mAh cells could be 2000mAh in real life depending on the tester, as you know.

Well yes and no as far as tester correction factors. As you know I have done some meticulous testing of the "Testers" and am continuing to do so.
The Zanflairs are out of the picture as way to high of results constantly +8.5% to +10%. So I am left with the OPUS, LiitoKala and Foxnovo.
The OPUSes I have seem to be a max of 4% high. The LiitoKalas closer to +5% max and the Foxnovos -3.5%. I have 3 LiitoKalas, 3 OPUS, 4 Foxnovo and 1 SkyRc. 1 LiitoKala and 1 Foxnovo are dedicated to the Sony Green Cells "Suck" experiment as well as the SkyRc every so often.

I mean it is easy enough to write a column in excel and take ~5% off of the OPUS and LiitoKala results and then sort with that.
In the meantime I will continue my quest, as you suggest, for the 2200mAh and up holy grail as I am fortunate enough, as you say, to have a steady supply of batteries.
I think I am going to purchase 4 more brand new 2200mAh cells to run through my testers and see what the results are again. It is always a good reality check to be able to say yes I do have confidence in my testers and know the approximate deviation plus or minus.
At one point in time or another there has to be a "Reference" piece of equipment that is the standard and at this point in time it is the SkyRc. I do find it very consistent and really close to the cells (Brand new cells) advertised capacity especially if following the manufacturer's spec sheet on how they tested the battery and under what circumstances to get the results they advertise. I also just ran my 4 Samsung INR18650-25R test cells through an iCharger X6 (yes 1 at a time) and the results were very good  not quite -3% but very consistent.


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 3/23/2019
Total Number of Cells           3743
Cells  >80% of Capacity        2445
Cells <80% of Capacity         1265
Cells ≥2200mAh & ≥ 80%     1709
Google Drive for info https://drive.google.com/drive/folders/1...sp=sharing
Not your average Wolf       
            Cool



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#8
@Dallski a 2000+mAh cell is still a good cell no matter where between 2000 and 2200 it actually situates.

Exception to this is testing high current power cells at low discharge values (Like 10,20A tested at 1A or under). If any cell has capacity under the specs at a low current test it will be unusable in a high current power tool. In this case having 2000 instead of 2200 means the cell must be no longer used for power applications.

@Wolf are you selling some of your cells or you plant to stack large quantities and used them in various projects of your own ?
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#9
(02-28-2019, 01:16 PM)Overmind Wrote: @Dallski a 2000+mAh cell is still a good cell no matter where between 2000 and 2200 it actually situates.

Exception to this is testing high current power cells at low discharge values (Like 10,20A tested at 1A or under). If any cell has capacity under the specs at a low current test it will be unusable in a high current power tool. In this case having 2000 instead of 2200 means the cell must be no longer used for power applications.

@Wolf are you selling some of your cells or you plant to stack large quantities and used them in various projects of your own ?

The chemistry of high current cells is mostly in the INR and IMR chemistry group. You won't find many if at all any in laptop battery packs. Power Tool packs yes.
I have 80 INR18650-13Q I pulled from a bunch of tool packs that have very low IR as this chemistry has the low resistance of manganese and the high energy of nickel. I will more than likely build a ~12V pack with those cells and it will have good high drain capability without much temperature.


The cells I am working with mostly are ICR chemistry which most of them (again the exception proves the rule) have a manufacturer's "standard" discharge rate of ~400mA to 600 mA usually .02C of rated capacity. That is also the discharge rate that "most of these batteries" are rated at for their mAh results.
That is not to say that a discharge rate of .5C or even 1C wont produce close to the desired results. But more heat is involved.
More than likely I will keep the INR chemistries and high drain capable cells out of my packs as it will influence the IR of the whole pack by reducing it to an artificially low level. as most of the INR cells have an IR of <30mΩ and the standard ICR cell chemistry usually runs around 50mΩ to 80mΩ.

As far as selling my spare cells certainly. I do have a personal pride rule though! I will give away all cells that I have that test out with less than 80% of rated capacity on the OPUS, LiitoKala, and Foxnovo. The rest with over 80% of rated capacity I will sell when the time comes. The buyer has the advantage to be able to look up the cell # on my google drive "Harvested Cell Analysis.xlsx" Excel file and under the "IR & V Before Capacity Test" Sheet find the cell and see what its history was.

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 3/23/2019
Total Number of Cells           3743
Cells  >80% of Capacity        2445
Cells <80% of Capacity         1265
Cells ≥2200mAh & ≥ 80%     1709
Google Drive for info https://drive.google.com/drive/folders/1...sp=sharing
Not your average Wolf       
            Cool



Reply
#10
Wolf, if you are already tracking which tester and slot you use to get each test result, I would suggest using correction factors in an additional column to get "true capacity." That way you are not including a 2150 cell and rejecting a 2250 cell if that makes sense. Also, another option for you if you want to include cells down to 2000mAh is to increase your pack size. You can easily add 20P to your 14S 200P by including those 285 cells between 2200 and 2000mAh.

Overmind, I was just referring to the cell topic where Wolf was thinking about upping his minimum cell capacity from 2000mAh to 2200mAh. I don't disagree that a 2000mAh cell could be a good cell. Wolf has 285 cells that are between 2100mAh and 2200mAh. A few mAh here or there can make a big difference in the number of cells that make the cut.
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