Ok thanks guys I really appreciate this but Doc, you're fine explanation puts another little doubt in my mind. You say to group the cells together with voltages that are 300 mv of each other which makes sense. 2.5 to 2.8 and 2.9 to 3.2 and so on. But in your very first post, you say to basically toss any cells below 3V. I hope I can use the cells that show a voltage of less than 3V because after opening 14 packs, I have 12 that were dead (I expected more so that's good) and 58 that are between 2.3 and 2.8 volts. So can I use these cells? My thinking is that if they show a voltage and charge up to 4.1V with no problems than they're good. But of course to know exactly if EVERY cell takes a charge and is good to go, than this brings me back to charging individually
Thanks for your patience, I'm old and presently sick with the flu so brain working at an even lower level than usual.
the cells spec say use between 2.5 to 4.2V max voltage range.
Usually we recommand any cell that charge up to 4.2V to have a low cut off at 3.0V, but 2.5 is still good.
Yes you can use the cells that are 2.5V and above.
One of the thing you could do is to equalize all them ( that are above 2.5v when you receive them), reject all cells under 2.5V.. or keep them for boost pack, or other use.
Once they are equalized ( at least 12h later if you use the sandwich parallel connection method)
it's time to remove them from the sandwich conections (unparallel them), leave them alone for another 12h and then, measure their individual voltages. The one that are out of the average voltage must be rejected, these cells are probably weak and selfdischarge abnormally.
When i mean out of the average i mean if the amost of the cells are at 4.15V after the total 24h hour and that you have some cells that are at 3.8, 3.9 or 4.0V, these cells must be rejected.
Than you can be sure that all the rest of the cells are good for your ebike use.
Please note that this particular method is not followed by the average of person that use the konions and they are still satisfied of the result. But if you wnat to improove the performance of your pack, then, following the most of the mentionned steps will certainly help!
I tested ALOT of Konion cell RI and Capacity and i know that if you follow this method, it will give you the results really similar as if you would measure all capacity and Ri of cells and match them. These cells are robust!.. the only thing they dont like is heat above 50 celsius that can reduce their life, nothing more.
In fact, Ri, Capacity, and age of lithium cells are all in relation. I wrote alot of documentation and test about that in E-S.
Normally a cell that have high RI ( not good) will self discharge faster and have a low capacity.
But sometime it happen rarely that you can have a cell with very high capacity but not so good RI... but it is rare and is more related to the irregularity of chemistry and cell fabrication process.
Also the if you use a method to measure their RI , the result you will get might be different than the one of another E-S member will have. The RI is affected by ALOT of parameters!! so if you wnat to use an absolute RI testing method or device, it must be described cristal clear!!.
Temperature of 2 or 3 degree variatin will make a significant change in RI, and also the time you allow them to stabilize after their last charge, as wel as the method you use. AC impedense DC resistance are two similar but not identical method so if you want to compare your results, IT MUST be done in the same process and using the same calibrtated device.
If you measure the RI to perfectly match the cells, it doesn't matter the method you use , but it must be constant and followed precisely for all cells and under the same condition.
The past results i used for my 432 cell pack was done with my modified RC megapower 960-SR charger discharger that was using the Kelvin 4 wires method.
See teh thread: https://endless-sphere.com/forums/viewto ... =14&t=2764
I joined two really important file you can use as reference that was made with over 170 Konion cell pair.
Yes you can leave the cells paired if they are in the pack ! Dont forget otherwise you will double your work time!
Cells in pair have the same age, same state of charge and are already matched together!
I hope this help!