how-to salvage old cells?

stanelie

100 µW
Joined
Jul 29, 2022
Messages
8
Hello.

So, I just got this 2011 Zero DS motorcycle with a dead battery pack that I replaced with Nissan Leaf cells. I would like to salvage what I can from the dead battery pack.

It is composed of 312 IMR-26700A from Molicel. The pack has been over discharged, most of the cells are lower than 0.5 volts.

How do I go about recharging them at ultra low rate to bring them back up at a safe voltage to be properly recharged? I don't really want to do them one by one, with 300 of them.

Same goes for a proper charge afterward, and then for testing their capacity for matching purposes. What can I use to somewhat automate the process, or do the charging/testing in bulk?

Thanks for any tips!
 
Any cell discharged that far is internally damaged and may be a fire risk. (there is no nondestructive way I know of to test for this kind of failure until they actually start a fire; if you find one please post it; others trying this could use one). I'd highly recommend recycling them, because the risk of fire, while small, is extremely high-consequence and can't be stopped by you once it starts.

If you do decide to try to reuse them anyway, keep in mind they will never be like they were; they'll have higher internal resistance, more voltage sag, less capacity, less current-delivery capability, more heating during charging and discharging, etc. I'd also recommend keeping them always outside any dwelling, etc., away from where any fire that ever did happen could never hurt any living thing.

The damage done inside them is not visible without destructive testing, and a failure could occur at any time after the damage has been done, but because of cell heating is more likely to happen while current is flowing, fire is more likely during charge or discharge. Charging is more likely to be fatal to you or others, because people are careless during charging and leave things unattended, and do this in or near their and/or others' dwellings.

If all the cells are the same dead-dead voltage, you can parallel them all and recharge them all at the same time at some extremely low current of a few mA per cell.

There are some threads around here where people do automated testing of batteries (pajda, batterygold, camlight, etc), so you can check out their equipment and methods for that. Some of the threads are listed here
https://endless-sphere.com/forums/search.php?keywords=test*&terms=all&author=&fid%5B%5D=14&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search
 
Hello.

Thanks for the important warnings and caveats, I will keep those in mind when deciding on the applications for those salvaged cells.

Is there equipment I can get to do bulk operations on these cells to help me sort them? I now know I can trickle-charge them in parallel to a safer voltage, I can get a bunch of chargers to charge them, how do I test their capacity and characterize them in bulk? Or do I have to discharge them one at a time?

Thanks again.
 
stanelie said:
Is there equipment I can get to do bulk operations on these cells to help me sort them? I now know I can trickle-charge them in parallel to a safer voltage, I can get a bunch of chargers to charge them, how do I test their capacity and characterize them in bulk? Or do I have to discharge them one at a time?
Have you looked at those threads I noted?
 
stanelie said:
The pack has been over discharged, most of the cells are lower than 0.5 volts.
Cells <0.5V are over discharged by definition, no?
 
Did not read the whole thread.

Do not try this, at home or anywhere.

Boom Bad!!

Recycle and buy New, Grade A, matched cells ideall from the same production run.

If you really can't afford that, you can't afford this hobby yet,

save save save, hustle until you can
 
Well,

I've heard a lot about the dangers of over-discharged lithium batteries, lots of people talking about it, but never anyone showing actual data about it. So, I did some research and came across this great explanation, as well as a the mentioned research paper about it published in Nature (a serious and renowned scientific publication for those who don't know) :

https://www.youtube.com/watch?v=sRwoYJyjZNo
https://www.nature.com/articles/srep30248

Not as bad or extreme as one would think.

Basically, charge slowly to a safe voltage (3V) and then charge normally, and be on the lookout for self-discharging cells after a few days. Those are the bad and potentially dangerous ones.

Let the troll/flame war begin.
 
nicobie said:
Myself, I wouldn't take a chance on them. Time for the dumpster!
Would you actually toss 312 IMR-26700A Molicel no-good lithium cells in a dumpster or take them to a recycler? Time to unload them.
stanelie said:
Not as bad or extreme as one would think.
The overdischarged cells in the two sources you posted still had hope of recovery (e.g. 2.19V). There was no inference in the youtube or article that lithium cells with a resting voltage as low as 0.50V to 0.00V (NO bounce back voltage) are salvageable.
stanelie said:
Basically, charge slowly to a safe voltage (3V) and then charge normally, and be on the lookout for self-discharging cells after a few days.
Nothing in that youtube or article came anywhere close to implying Li-ion cells having a voltage as low as 0.50V are salvageable.
99t4 said:
stanelie said:
Let the troll/flame war begin.
Why do you expect that?
Maybe he likes playing with fire.
 
stanelie said:
Not as bad or extreme as one would think.

Basically, charge slowly to a safe voltage (3V) and then charge normally, and be on the lookout for self-discharging cells after a few days. Those are the bad and potentially dangerous ones.

AFAICT, the paper you've linked isn't about cylindrical cells (it's about large-format cells, which are not quite the same; mechanically there are various differences, including how they respond to various conditions). Also, as noted in the paper about the EV cells, it's even possible that some of them have reversed charge at some point (you cannot know what has happened to them before you got them, or how they were used or abused, etc., and not knowing any of that, along with their present condtion, would show me that the risk is too great vs the possible reward.

As a side note: Years ago, I was able to recover a few large-format EV cells (EIG C020) from severe overdischarge....but I would not do it with cylindricals. Even so, they didn't perform the same afterward. The large-format cells will puff when something goes wrong in them (when they are not built into a pack, such as when disassembled for testing), leaving visible signs that something serious is wrong. That said, I wouldn't do this again, just because of the potential fire risk.

Cylindrical cells do not typically have any visible signs that something has gone wrong. If they have a valve to release overpressure gas in them that disconnects them internally electrically, permanently, then they're "fail safe" for the specific events that create that overpressure gas. But if they're not made that way, or the event they experienced did not create overpressure sufficient to pop the vent and electrically disconnect their internals, then they could still represent an unknown hazard.


The risk of an actual fire is small, but the consequences are disastrous.

Once the fire starts, you're not going to be able to put it out, and you can't wheel the bike or carry the battery away from wherever it is; a battery fire is too big and too hot..

If it's in a building, that building is going to catch fire, too.

If there are living beings (people, animals, etc) in it, there's a significant risk of them dying horrible deaths from this fire, which will be caused by you, and you will have to live with this, if you aren't killed in it, too.

Could you live with killing others just to save a few bucks, if it did happen?

Sure, this is worst-case, low-probability. But the possibility exists...

It's up to you to decide what to do; hopefully nothing bad will ever happen. :)
 
Well, moot point I think.

I've measured the capacity of a few "salvaged" cells, and they are far from the supposed 2900 mah specification. I've measured them between 1200 and 1400 mah.
 
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