Reviving Lithium Battery Cells | Salvaging 18650 Cells

What if I told you that you could get decent lithium (Li-Ion) battery cells for much less than new - sometimes even for free? In this episode we continue salvaging battery packs, and we'll try to revive our 18650 cells. Some can be charged straight up, some will need pre-charge cycle, and the most extreme discharge cases will require external boosting in order to kickstart the process. Stay tuned! [Use chapters if you want to jump to a specific section]
Li-Ion (lithium) batteries can be expensive if you need a whole bunch of them for your project. But in many cases there is no real alternative as lithium-based chemistries give the best performance as far as capacity/weight etc. Enter salvaging lithium cells project! We will be primarily working with 18650 cells (cylindrical cells 18x65mm). These cells can be found in laptop batteries, powertool packs, modem batteries, medical equipment powerbanks etc. When this equipment gets discarded, you can get these packs for cheap or even for free. So in this project we source some old packs, shuck them, deconstruct into individual cells and then try to revive these cells and see what can we get out of these cells in terms of performance. We'll take a look at a way of cataloguing the haul as well as analyzing charging profiles to determine what makes a good salvaged cell, and what should be discarded. So stay tuned!
Don't forget to like and subscribe if you found this useful and would like to see more. Let me know in the comments what you agree/disagree with, what you liked, what you didn't like, if you have any questions, if you know of a better way of doing it, or if there is something that I absolutely should not be doing or have done ;) All constructive feedback is welcome! ;)
Disclaimer:
This video is only for entertainment purposes. Any injury, damage, or loss that may result from improper use of tools, equipment, or from the information in this video is the sole responsibility of the viewer.
00:00 Overview
03:56 Regular refresh charging setup
09:22 Sample results and analysis
17:52 Charging almost dead cells
20:03 Boosting deeply discharged cells
23:46 Success - thanks for watching!

[@ericklein5097]

The way you are boosting these is the exact opposite of what you should be doing to an overdischarged cell. The Samsung datasheets and even the TP4056 module lay out the proper way to handle an overdischarged cell
1. 50mA up to 2.50-3.00v. It can take a while after 2.50v so if that’s the minimum of the cell then you can increase the current once you hit that point to 250mA or something like 0.1C max
2. Check to see if the cell holds voltage at 2.50v. If not, it’s self discharging too fast to risk going further.
3. Don’t charge all the way up to 4.20v. Stop somewhere after nominal just to do another self discharge check.
4. If it’s still holding voltage then continue a relatively low current charge to 4.10 or 4.20v. Up to you but I prefer to stop at 4.10v and let them sit.
Paralleling cells with a voltage difference is a big no no. It’s good that you aren’t using a full charged cell but the currents you could be injecting into the lower cell can be immense. Thankfully those alligator clip leads are often made with tiny wire and offer tons of resistance but you could still be causing a momentary 5A or more to enter an overdischarged cell. I’ve tested cells at 3V and 4V and using 14AWG wire it would initially start out at 20A before trailing off to 5,4,3A but that’s still wayyy more than any cell should be charged with.

[@JustMakeItNow]

First of all, thanks for contributing! I am not sure though why are you saying that what I am doing is the exact opposite of what should be done. When I refer to boosting, I am strictly talking about fooling my smartcharger to accept the cell into pre-charge cycle, which has a cutoff of around 1.5V (don't remember exactly). Once charger accepts the cell, actual charging happens pretty much along the same lines that you posted (precharging with 0.15A till 3V, then switching to a regular charging program as specified), and has nothing to do with the booster cell. Now, while stopping along the way at 2.5V, 4.1V etc for intermediate testing might be fine if you're working with a few cells, but no way I am doing that for several dozens or hundreds cells manually ;) If I'd have a custom charging circuit that would incorporate that logic that would be fine, but no standard chargers that I know of (including RC3000) support that. So it's just not very practical.
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Now, paralleling cells is definitely not something that generally should be done, you're right about that. I believe I do talk about it (though maybe in a different video). Now, for the purpose of showing up some voltage on the charger terminals ideally I'd just use a current-limiting power supply, with something like 2V and very low amperage limit, but I didn't have one handy (the lowest I could go was 1A, which was too much IMO). Hence this almost dead cell was used as a voltage booster for a few seconds. So that cell had slightly above 2V (?) to begin with, so no way even with no-resistance leads it would be outputting multiple amps, and you're also right that these leads wouldn't support that either (tested that before). I am pretty sure I even measured short circuit current on the booster cell, and it was pretty low. So while it was certainly not the most robust setup I admit, it was not as bad as you may think :)