Cells less than 1v but low internal resistance - worth saving?

deswong

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Jan 20, 2021
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Hi all,

I have finally gotten my RC3563 today and thought I would test some of the cells that I have been binning over the last month out of curiosity.

I have been simply measuring the cell voltage and if the cell is less than 1v then it gets binned - based on previous feedback and various posts in the group.

Testing a few of these cells that are under the 1v threshold, all of them are of what I think are low internal resistance, ranging from 18-22 milliOhms.


This is one of many Sanyo UR18650RX cells that I have been binning.

Should I be keeping these and slow charging to bring them back up rather than binning them? I have just put 12 of them onto charge in the Opus, they are slowly charging with low mA.

Looking for advice if it is worth the time to bring them back to life, or just bin them?
 

Wolf

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The short qualified answer is Yes.

The qualifications that I go by is the age of the cell #1
Locate the date code on the cell and calculate the age. https://batterybro.com/pages/18650-date-code-lookup-tool
If the cell is relatively new as in < 3 years I will try to recover the cell. Most likely the cell did not spend a lot of time in the undercharged condition and will recover. The spec on this cell is <25mΩ so your measurements show a potentially recoverable cell.
1619695208668.png
Personally any cell <1V is suspect of having spent a little too much time in the "red" zone of discharge. At that low of a voltage there are some chemical reactions that take place that can compromise the safety of the cell.
If the IR is reasonable I do test every cell now no matter what the voltage is, more for experimental research and to learn. I filter these cells out of the final results and would never put them in my powerwall.
As you can see by the chart below the mAh results are also somewhat reduced most of the time.
I would not shy away from using these batteries for single cell use.
Wolf
1619696735605.png
 

deswong

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Jan 20, 2021
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The particular cell that I had tested there, came back with this result after putting it through the opus:

RC3563 resistance: 12.505 milliohms
Capacity: 1953mA

I've thrown away at least 100 of them! Now I have a tester this will save me from throwing out so many!
(I'm not at powerwall state yet, just cell harvesting and sorting - still!)
 

daromer

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I test all my cells for capacity. As have been said numerous times before and that is that voltage is not definition of neither health nor actuall capacity. Its just a potential inside the cell. With that said we see alot higher number of cells below lets say 1.5v or what not that is crap compare to 3.5+ :)
Unless the lithium is drained low for sitting long time since they are discarded they may have had a faulty bms that drained them faster and thus most likely can be brought back to life.

IR and total capacity is so much better values for testing SOH where they combined is the best way of determining the number of cycles they potentially have made :)
 

FarmerJ

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I’m new to cell harvesting and testing and have been watching videos for over a year by Jehu, HBPowerwall and others, reading threads on here and other sites, and collecting battery packs, chargers/dis chargers to start my own projects. This is my first post on here. In all that I’ve read, watched, researched, there doesn’t seem to be a lot of consistency in information on IR. I actually came to ask: What is the correct point for testing/measuring the IR of an 18650 cell? I get totally different IR numbers from cells I’m just harvesting that are at a low SOC vs after charging them. I’ve had cells that initially after harvesting show 125mΩ IR at a low SOC on my Liiitokala Lii-500’s and then after charging if I unplug the Lii-500 and plug it back in or push the batteries off the contacts and let them seat back the IR drops as low as 10mΩ but usually in the 24-50mΩ range depending on the cell model. Is the IR shown by the Lii-500 even reliable as a number? If I disconnect and reconnect the cells multiple time I get different values for the IR by a few points each time, so I’ve kind of been recording multiple numbers for each cell while I wait for the YR1035 I ordered to arrive.
 

floydR

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no the IR returned by a Lii-500 or opus, most multi slot tester are not reliable.
Later floyd
 

Wolf

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In all that I’ve read, watched, researched, there doesn’t seem to be a lot of consistency in information on IR
Not sure what you mean by that. I think there is plenty of information and discussion esp. on this board on IR and its importance on determining the SOH of a battery from first touch. There is a cheat sheet of recommended IR values for most popular cell numbers https://drive.google.com/file/d/1n6DU0VC7Yjksz2ah90VUcpw6SW6kFqQt/view?usp=sharing
There is also plenty of discussions on IR and how to properly check it and what tools you need. All slide testers that claim being able to test IR are DC voltage drop IR testers which require a reasonably charged battery to give you an "estimate" of IR mostly wrong and certainly not repeatable. Just squeeze the slide on the testers and you will get a different IR reading. Or as you have found out getting multiple results from the same cell. Once you get your YR1035 you will have an accurate and repeatable IR reading that you can count on and quickly make a determination whether the cell is worth pursuing or not.
Additionally a proper IR reading at that low of an ohmic value needs to be done using a 4 wire kelvin method which the YR1035 and several other 1kHz AC impedance meters are designed for.

Wolf
 

italianuser

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Yes, @Wolf does an excellent job with cells, his strict procedure for selecting cells will give you a good quality result.

I agree with @daromer, cells with real low voltage not necessarily are trash; chemistry could still be good. I personally try all cells, if they are really low on voltage I try a low amp recharge up to 3V. And if they keep the voltage (that is: they don't go down again real low) I will try charging them a first time and measure the results.

Experience will tell you which cell to keep and which not. Thanks to all info on the forum my procedure for selecting cells now starts to make sense:
- Heaters: I'm more strict than the flowchart posted in another thread (sorry I don't have it under hand right now); if they go over 40°C I discard them. Why? Because all my other cells at 1A charge don't go so high with temperature. When I take a heater out of the charger I have difficulty in holding it in my hands without moving it around and that means temperature is too high. I don't trash them, keep them for testing.
- My policy for re-wrapping cells sucks: I'm not ready to rewrap all cells right now, I'm at my first pack, it won't be perfect LOL.
- Check for rust on cells if this: I inspect cell using a strong light. Any marks, stains, darker colours on the cell's exposed parts will make me mark that cell and put it aside for trash. One day, when I'll be into re-wrap-em-all process I'll be happy to check all cells.
- Dents and visible damage to the cell: discard, keep them for testing.
[ Sorry maybe I went a bit OT! ]
 

FarmerJ

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Not sure what you mean by that. I think there is plenty of information and discussion esp. on this board on IR and its importance on determining the SOH of a battery from first touch. There is a cheat sheet of recommended IR values for most popular cell numbers https://drive.google.com/file/d/1n6DU0VC7Yjksz2ah90VUcpw6SW6kFqQt/view?usp=sharing
There is also plenty of discussions on IR and how to properly check it and what tools you need. All slide testers that claim being able to test IR are DC voltage drop IR testers which require a reasonably charged battery to give you an "estimate" of IR mostly wrong and certainly not repeatable. Just squeeze the slide on the testers and you will get a different IR reading. Or as you have found out getting multiple results from the same cell. Once you get your YR1035 you will have an accurate and repeatable IR reading that you can count on and quickly make a determination whether the cell is worth pursuing or not.
Additionally a proper IR reading at that low of an ohmic value needs to be done using a 4 wire kelvin method which the YR1035 and several other 1kHz AC impedance meters are designed for.

Wolf
Thanks! It was reading stuff on here from you that made me order the YR1035 and actually start paying attention to the IR numbers at all. I just haven’t seen good explanations of a few different things I question about IR but maybe I haven’t read enough yet as I haven’t gotten into anything related to building packs and matching cells together. It is good to have someone confirm that the variance I get with the LiitoKala is due to the method and device. I’ve charged close to 1800 cells already and have dates on each of the 20 cell holders for when they completely charged so that I can check 30 days later for self dischargers. Then I go through the NOR test on the LiitoKala’s at 1000mAh and log the results sorting the cells out into capacity ranges for later.

I really appreciate the reply Wolf!
 

Wolf

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@FarmerJ
Several things...............
Charging 1800 cells is a great achievement in itself! That means at least 260 laptop packs have been opened and cells liberated. 👍
Also they didn't find themselves in a landfill and that's good.
The best thing you can do with the 1800 cells is when you get your YR1035 is test the IR and compare it to the cheat sheet.
Also if the cells are from laptop batteries hopefully mostly OEM, as the aftermarket replacements generally have "generic" cells, trying to be politically correct here, (Chinese cells) that are somewhat substandard. Although every now and then they will surprise you.
Nevertheless HP, Dell, Acer, Toshiba, etc. will generally have quality cells.
The chemistry will most likely be ICR or NCR which means the "normal" true IR of a "good" cell will be in the 30mΩ to 50mΩ range. There are some exceptions as in the LG 2200mAh (LGEAS31865, LGES318650, LGAAS31865, LGDAS31865, etc you get the point) that have an IR of >50mΩ and seem to perform just fine. Personally The IR is a bit to high for my taste for a powerwall but if it was the only cells I had I would use them.
For a successful powerwall battery especially with a multitude of donor cells i.e. many different part numbers from different manufacturers affectionately called a "Frankenstein" battery it is best to stay within a certain IR and mAh result. Can you pair a 1500mAh - 15mΩ cell with a 3000mAh - 35mΩ cell? Certainly but you would be putting baby legs on a muscle man. The ideal battery would have all the same cells with all the same IR and all the same mAh results. In the real world especially when salvaging cells that is not possible. Also to keep within the OP subject matter you will have cells that will be below 1v. If the cells date code is less than 3 or possibly 4 years its worth testing especially if the IR is good.
So in essence if you stay within ≈ 85% SOH, a 15mΩ spread such as 35mΩ to 50mΩ, and a mAh spread of ≈500mAh equally distributed throughout each pack you should have a very successful "Frankenstein".
Quick note: The LiitoKala is capable of charging at 1000mA but max discharge is 500mA hence it has no cooling fan like the OPUS.

Wolf
 

italianuser

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... and log the results sorting the cells out into capacity ranges for later.

I really appreciate the reply Wolf!
Oh yes, if you log stuff you surely go well with Wolf 😅 😅Welcome to Lithium Addicted & Loggers LOL
 

FarmerJ

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So far the majority of my cells come from Arris Modem packs with 4 cells. It’s a mix of:

LG LGDAS31865
LG LGAAS41865
Sony US18650GR G5
Sanyo UR18650A
Sanyo UR18650F
Samsung ICR18650-22
Samsung ICR18650-22P
Samsung INIR18650-29E
Moli ICR-18650H
Moli ICR-18650J

I’ve broken down 600 packs and about 10% of the LGDAS31865’s have their CID tripped and about 15% have a voltage < 1.5v. I figured on just recycling all of those cells but if the YR1035 IR is in spec I’ll try recovery based on this threads information.
 

Wolf

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