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Development of a free Capacity Predicition, need your help
#31
(05-26-2019, 06:26 PM)100kwh-hunter Wrote: @wolf
As you know i keep a very close eye on your work.
So that is the eye in the sky I keep seeing when I turn around.

I'm going to turn all my cameras off.

Quote:But i can not help myself to ask the following question, its playing for a very long time in my mind:
Why did you never tried to make your own charger/discharger to get optimum results?
With your knowhow it must be a peace of a cake!
There...... finally got the guts to askSmile
Had I known 8 months ago what I know now I probably would have. But alas I jumped in without forethought and bought a bunch of charger/testers. Little did I know what I was going to get involved in. Now that I am about 10 cells away from my 2800 cell goal I will devote more attention to putting something together like that. This weekend I put together a nice ZHIYU® ZB206 board so I am working on more testing equipment.
 

Quote:By no means i want to offend people and i am in doubt if this is way off topic.
Sinds we must trust charger/dischargers?

Very good read!
Best
On my Vacation to Austria from the 15th of June to the 3rd of July to visit my mother I will immerse myself into Arduino code and RPi and play around with that. Notwithstanding the mountain climbing trips and general relaxing.
We will see what becomes of 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 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       
            Cool
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#32
(05-21-2019, 02:30 PM)Wolf Wrote: @drbacke
Interesting predictions and not to far off.
Good work on the model.
The predictions are close to what my tests show. Good stuff!!!

My cut off on those cells(UR18650FJ) is Optimal ≤68mΩ and Marginal up to 76mΩ
There is only 1 thing I do different with any <1V cells that are within my acceptable mΩ readings.
I charge them in parallel at a CC/CV of 4.2V at 50mA per cell.
This usually takes a couple of days if not 3 or 4 before they come up to voltage.
If a cell gets remotely warm during the 50mA charge it is taken out.
These happen to be UR18650FMs and not a heater in the bunch "yet". all cells <58mΩ.

Once they hit 4.19 they will rest a bit and I will retake the IR and then into the charger/ testers they go.
I label them with a yellow font in my spreadsheet that way we know they were low voltage cells to begin with.
Once in the charger/testers charging the rest of the way to 4.2 at 500mA that is where we will see if there are any heaters.
Most of the time they behave very well. We will see.
I have now started to change the font color of the "known" heaters that make it through the preliminary IR tests in the tested capacity to red.
As you can see I only have 4 so far. All the other ones never made it this far. I do still have a boxload of ~300 of them of all various makes and models but mostly Sanyo.

How did you charge the UR18650FJ cells?

Wolf

It may be the wrong thread to start a discussion about it, but you have so woderfully and thoroughly descriped your approach of reviving low-U cells.
I did already in the past offer "sceptical interest" because your process links the cells together and do not treat them "separately", but however in the end the success beats the science.

I come back to this because it didnt leave my mind to try to understand what this process does in effect, and what makes it so obvious successful in your case.

For once i have new "strange" positive results in even lowering the starting current (see my lucky thread), and reading your nice desription again i found a new insight which help unterstanding better what tricky thing you do.

What i found is, that (in the end) good cells come up from even 0.6 V per cell in an amazing dU/dt , taking some 3 mAh (only) to come up to some 2... Volt. Only then they start to slow down in dU/dt taking up charge and storing it properly in the intended chemical processes. 

My thinking (which is yet to be "proved", it is only hypothesis) came to the idea, that "future" "bad" cells may have already damages in the separators, or "dearranged" chemicals which will not anymore take part in the storage process or even distort that (like copper dendrites).
These damages or dearrangements may take charge without essentially storing them, so being losses. That would slow down the dU/dt value, being an indicator for good or worse cells.

Now coming back to your method, in essence it (perhaps) can be looked like you indirectly compare the dU/dT of twenty cells, by distributing the current to the cells having equal dU/dt, so giving more current to the bad ones, giving them more losses, which can be identified als heat.....Big Grin
(The Genie Idea of Wolf is just comparing good to bad cells, instead of scientifically determining what is good or bad)

Now, your 50 mA is quite high compared to the 2 mA i used. There is lots of rooms for more experiments.
A last thought may be a very low cells may have a very slow chemical speed to take even the low currents, and any "excess" does "damages".

I look forward to what you may say to this considerations, and if Wolfs obvious succesfull "sorting" arrangement is only a sorting or even more....
(what means probably there is a limit of current where more is itself damaging the Low-U cell more)

One thing more - perhaps it would be a good idea to transfer this and many other things to the Low Voltage thread which is just newly created.
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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