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Does internal resistance matter?
#11
(12-12-2018, 01:35 PM)batteryq Wrote: Thank you guys for all the great info!

I too find some of the devices which claim to be able to measure IR are not as accurate as one would hoped. I used Liit and zanflare, same battery the IR reported are about 50-100mOhm different, with zanflare always higher than Liit. I am not sure which one to trust.

At minimum, do not trust them if it is not 4-wire.


https://en.wikipedia.org/wiki/Four-terminal_sensing

If they are, i can tell its higly dependant from temp, and method.

So, if it is stable, when you do 10 contactings, its most probably good.
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#12
Here is a spreadsheet with the IR and mAh results of 4 brand new Samsung 25R cells tested with 6 different testers.
The commercial YR1030 is used as a reference that I trust.
The LiitoKala and the XTAR Dragon seem to be the closest.
Now I do notice that when I check recycled cells esp. the ones that have the remains of the nickel artifacts on the positive and negative terminals the readings are definitely different. Much higher in most cases on all the testers.
That being said the LiitoKala and XTAR Dragon (with its separate probes) seem to still be really close.

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
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#13
(12-12-2018, 02:21 PM)Wolf Wrote: Here is a spreadsheet with the IR and mAh results of 4 brand new Samsung 25R cells tested with 6 different testers.
The commercial TZ1030 is used as a reference that I trust.
The LiitoKala and the XTAR Dragon seem to be the closest.
Now I do notice that when I check recycled cells esp. the ones that have the remains of the nickel artifacts on the positive and negative terminals the readings are definitely different. Much higher in most cases on all the testers.
That being said the LiitoKala and XTAR Dragon (with its separate probes) seem to still be really close.

Wolf


Wow, the IR of new cells ar so low..... never seen that. But, i have no new cells... Big Grin

Re Nickel artifacts, I got Research info that the welding points alone can be about 0.8 mOhm, and another piece of nickel strip be valued as nearly 2 mOhm, so on both ends together this gets indeed iteresting when you try to be absolutely accurate.
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4 kWh battery target - plus Mobile Home battery
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#14
That’s why I use the YR1030 as my true reference tool.
It has true 4 wire kelvin probes and you can bypass the nickel stalactites (or is it stalagmites) and artifacts and make contact with
the terminal properly.


 
It is also my first tool in my work area lol.




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
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#15
(12-12-2018, 04:19 PM)Wolf Wrote:  
It is also my first tool in my work area lol.




Wolf

You have a nixie clock. Definitely a must have in the work space  Smile
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#16
(12-11-2018, 10:29 PM)batteryq Wrote: Can't wait for your testing result!

The results you are waiting for.
After testing 522 cells and recording the results I can now definitely say that IR has a correlation with cell performance.
The results are here https://drive.google.com/drive/folders/1...3iSECb8iIs
Spread sheet is called Harvested Cell Analysis.xlsx and will be continually updated as cells get added.

Just look at the data and you will see how IR affects the capacity of the cell. Cells #1441 to #1487 was an experiment i did with around 100 ICR18650-22F cells. I set aside the 45 cells with IR of 60mΩ or below and tested them. Take a look at the results. No really take a look at them!
I'm not here to convince anyone of the importance or IR measurement to save time and bin cells you know are going to be poor performers and maybe revisit them at a later date. But if the cell has > 1V and the IR is aceptable you will more than likely not have wasted your time IMHO.

As this spreadsheet grows to 1000 and up cells, the answer will become clearer and clearer and users will only have to sort by cell manufacturer or model number to see where their IR stands and the cutoff for performance is.
If you have MS Excel download the sheet and play with it sort by IR, sort by mAh rated and results,etc, build scatter charts and correlation graphs it fun to see how this data can be used.

Again I am not going to try to convince you that the first thing to do is check IR with a Proper Kelvin 4 wire IR measuring device and if you got a YR1030 tester it will give you voltage as a bonus.
But I know what my cell harvesting technique will be after I have completed this experiment and I have at least 3000 to 5000 cells in this database There will more than likely be irrefutable evidence how IR matters.


Wolf
Kna and Korishan 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 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       
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#17
600 cells later I have more graphs on IR and capacity.
By now you all know I test all my cells IR and voltage with a YR1030 4 wire Kelvin meter. Just in case you are wondering.
Each graph depicts one cell type and manufacturer. Indicated on the chart title. Well just the cell model number but by now I just about have them memorized.
You can make your own decisions on how IR influences capacity.  Tongue
It does appear that individual manufactures chemistry creates different results.
I can't wait to have 3000 cells in this database. but it's only me with 9 reliable testers. Sad
So that may take some time. Winter in Maine keeps me in the house anyway so it may go quicker.
Onward we go.  Wink




Wolf
cadric, DCkiwi, rev0 And 2 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 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       
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#18
Great Job!

We really need to consider how we link such info to the cell database

Maybe we don't need a full chart for every cell but at least the crossover point
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#19
(01-11-2019, 01:25 AM)Chablis_m Wrote: Great Job!

We really need to consider how we link such info to the cell database

Maybe we don't need a full chart for every cell but at least the crossover point
Chablis_m,

That is what I am working on I have just recorded my 700th cell. 1634 to 1700 (634 to 700) are waiting for the Testers but IR and Voltage have been tested. Now we wait for the mAh results.
What I'm trying to do is be able to get some baselines that are consistent and the more cells the more accurate this will get.
The results so far are very interesting.
As my initial thought was for 1400 cells for my wall I have now doubled the anti. Big Grin
I have a great supply of packs and will just slave away recording all the cells even though I know by the IR reading it won't perform to what I want. This info that I am gathering will hopefully be very useful to other powerwall DIYers. 
Im looking for at least 80% of capacity for my wall cells not just a 2200mAh reading. Any cell with less than 80% capacity remaining is really no good to me. But with a preliminary IR reading reading  of X I should be able to determine if this cell is worth the effort or not.
So thank you for your support and when there is enough data in the sheet I will post these graphs for all the cells that I have tested.
I would like to see at least 200 cells of each variety to be able to create these charts. Obviously the oddball ones I won't have that much info an but the mainstream cells definitely. After that, what the admins do with that information is up to them but the data and charts will be published on my google drive.
I think I will put the URL into my signature so it will be easily found.

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       
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#20
What a luck that you have been hopping in to my 4-wire IR introduction.
I do not have that supply of cells, and i never would have been able to supply that amount of specific and  accurate data.

I make a bow for the work you do.
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