Rejuvenating old lithium-ion batteries

[Connecteur]

I heard about the freezer trick for getting old lithium-ion batteries to work again.  I very cautiously tried it by sealing the battery in a freezer bag and leaving it in the freezer overnight.  The next day it goes on the charger.  Always cautiously aware of potential thermal effects, I charged them in a protected environment, but so far, there have been no anomalies.

It appears to work about 80% of the time in the dozen or so batteries I've tried, and the capacity appears to be at least 70% of the original.  I store them in metal containers just in case, but there appears to be little danger of a thermal runaway.

I often buy older electronics at thrift shops and the like, and replacement cells are not always available or affordable.  I am satisfied that I have brought some of these devices back to functionality.  Much better than throwing them away.

[Doctorandus_P]

And then what?

You're going to sit next to your batteries with a fire extinguisher for a few years until they go off?

[wraper]

If you are talking about 18650 which became completely dead, then this probably allows protective gas pressure switch to connect terminal again. But if it already triggered, I would say those batteries are no longer safe to use.

[Connecteur]

I dunno, it just works.
I never leave anything unattended where it might catch fire, and after six months since my first attempt no mishaps at all.  After dozens of of attempts, it's still about an 80% success rate.  Most of the batteries have regained at least 70% of their original capacity.

I understand the safety concerns, but I have mitigated them, and I don't allow them to paralyze my actions.

I was hoping for a bit more constructive feedback on this phenomenon.

[BravoV]

I heard ....

Forget about it .... whenever every time people said about this words with some extra ordinary claim, yet without any proof, just a blind claim like ... "I heard, tomorrow the sun won't rise ... " ... see the pattern ?

I strongly believe you're smart enough to get what I mean.

[wraper]

never leave anything unattended where it might catch fire, and after six months since my first attempt no mishaps at all.

I doubt you leave them on a large piece of non combustible material during nights so there is no chance fire transfers to other things. The problem with bad Li-ion is that you don't necessarily need to do anything with them at the moment they catch fire.

[Siwastaja]

18650 cells can work as projectiles, though, so whenever I work with iffy cells, I put it inside a metal tin (which is significantly heavier than the cell, or otherwise physically restrained), and put that tin onto a non-flammable surface.

Even pouch cells can act as projectiles, not as likely but possible.

[AndyBeez]

never leave anything unattended where it might catch fire, and after six months since my first attempt no mishaps at all.

I doubt you leave them on a large piece of non combustible material during nights so there is no chance fire transfers to other things. The problem with bad Li-ion is that you don't necessarily need to do anything with them at the moment they catch fire.

It's a nice technical lab experiment, but not one I would repeat off the bench.

On remanufactured lithium batteries, these have a habbit of being welded into battery packs with other 'second life' cells, which are sold on in legitimate/counterfeit low cost battery packs for e-scooters.

Cells are sourced from hybrid vehicle packs (either service expired or insurance right off) and from less certain sources such as scrap consumer devices (where the cell was already reused). Often mixed together, budget battery packs have a basic BMS but will have no cell balancing. So it is a crap shoot if a cell will just go pop or, cause a fatal building fire by igniting all of the other cells in the pack.

Before anyone plays with used lithium cells, please read this:
"[London] Fire investigators issue urgent warning over fires involving e-bike batteries"
https://www.london-fire.gov.uk/news/2021-news/july/fire-investigators-issue-urgent-warning-over-fires-involving-e-bike-batteries/

For sale, one used e-scooter in charcol color:

[thm_w]

Needs more details:
- are these batteries with internal undervoltage protection that has tripped?
- are these raw cells?
- are you measuring capacity before/after?

I don't believe putting a raw cell in the freezer will have any effect whatsoever. If you measure <2V, its been overdischarged and its capacity is permanently reduced. You can slowly recharge it (as Clive does) and still have a useful battery, though.

I had some LG cells in a scooter battery pack (which were reclaimed cells already), one portion of the pack died (0.1V). The other portions of the pack seemed to survive OK, even being discharged to 2.1V they still have very high capacity, 2900-3300mAh.

[wraper]

I don't believe putting a raw cell in the freezer will have any effect whatsoever.

Why not? 18650 cells have protective pressure switch (CID) inside them that disconnects positive terminal when internal pressure raises above certain threshold. Reducing temperature decreases the gas pressure. Also it probably allows gases to leak outside because of seals shrinking and becoming hard at freezing temperatures. In the past I made dead cells working again by puncturing the CID membrane and thus release the gas pressure. Of course it was just an experiment and I did not use those cells but discarded them.

[uer166]

For sale, one used e-scooter in charcol color:

Interesting, looks like a Xiaomi m365, which is probably the highest quality scooter and properly designed/sealed pack and BMS you can get. I wonder what actually happened there. There is a total lack of actual investigation of root cause in these cases. It's easy to claim "oh it's a POS with used bad cells", but this is not one of those cases.

[thm_w]

I don't believe putting a raw cell in the freezer will have any effect whatsoever.

Why not? 18650 cells have protective pressure switch (CID) inside them that disconnects positive terminal when internal pressure raises above certain threshold. Reducing temperature decreases the gas pressure. Also it probably allows gases to leak outside because of seals shrinking and becoming hard at freezing temperatures. In the past I made dead cells working again by puncturing the CID membrane and thus release the gas pressure. Of course it was just an experiment and I did not use those cells but discarded them.

Was thinking about capacity only, but your point is interesting. Do you know how the cells you had had failed?
I would think that would be a rare occurrence, and as you say, if it did occur you probably don't want to be reusing the cells.

Heres a guy demonstrating it:

Interesting, looks like a Xiaomi m365, which is probably the highest quality scooter and properly designed/sealed pack and BMS you can get. I wonder what actually happened there. There is a total lack of actual investigation of root cause in these cases. It's easy to claim "oh it's a POS with used bad cells", but this is not one of those cases.

Its quite a generic design, many other companies are making them in that form factor.

[uer166]

Its quite a generic design, many other companies are making them in that form factor.

Good point, riding on someone's success and making crappy clones seems to be a business model for many.

[AndyBeez]

For sale, one used e-scooter in charcol color:

Interesting, looks like a Xiaomi m365, which is probably the highest quality scooter and properly designed/sealed pack and BMS you can get. I wonder what actually happened there. There is a total lack of actual investigation of root cause in these cases. It's easy to claim "oh it's a POS with used bad cells", but this is not one of those cases.

I agree. Blame exploding batteries, because that makes headlines. But a vigorous forensic investigation is too time consuming. With lithium packs in the hands and homes of the great unsupervised public, there needs to be a deeper understanding into the failure modes of these devices: Was a battery made bad or did it go bad after it was frozen in the street? Did the legitimate supply chain contain fake parts? Did the battery start the fire or did a BMS mosfet overheat? Was the charger used just a piece of Ali-crap? Questions... questions. There is testing, but I suggest the test parameters need to consider what idiots are actually doing to their batteries. Which is good engineering. But not cheap engineering.

[wraper]

Was thinking about capacity only, but your point is interesting. Do you know how the cells you had had failed?

Cells from usual dead laptop battery pack which failed because some cell(s) became open circuit. Bad or overcharged cells releasing the gas is a quite common thing, it's quite common to see puffed Li-poly packs since they don't have hard enclosure.

[Connecteur]

There's always an argument to be made for overconsumption; "just buy a new one, throw the old one away, it's not safe," etc...
But I'm a fan of recycling. I derive satisfaction from finding an older, interesting item, and restoring it to functionality.  More often than not, the battery has aged past the point of usefulness, and obtaining a replacement can be difficult.  That's when I discovered that the freezer trick works most of the time, at least to bring the device back to functionality.

When your livelihood depends on selling new parts, it's not surprising that the advice often points in that direction.

[wraper]

One thing is repairing what is broken, and that's certainly is how you should deal with what otherwise would be thrown out. Entirely different situation is taking potentially dangerous thing which deactivated itself because of becoming not safe and essentially bypassing its safety mechanism.

[uer166]

When your livelihood depends on selling new parts, it's not surprising that the advice often points in that direction.

Sorry but I call BS. When each cell is like a little flamethrower, you'd think twice before screwing around with it. Maybe try doing some destructive tests on say pouch cells, and hopefully gain some respect for it. When one tiny pouch cell is capable of giving you 3rd degree burns over a large area of your body, it's no longer about "overconsumption". And for the record, my livelihood has nothing to do with selling lithium cells, but I've seen enough (in a professional mass production context, I can't imagine how much worse shitty hobby RC stuff is) to know that when it goes bad, it goes bad.

[uer166]

People really overstate the durability of current-gen lithium ion cells. What really sold me on battery aging was to see the chart of capacity loss versus (change in) internal resistance

Do they? This is a solved problem, call your 80% "100%", and 20% "0%", just like they do in real EVs that have been out for >10years, and you don't loose appreciable capacity over the lifetime of the vehicle. People just need to collectively pull their heads out of their asses and actually engineer something. It's hard, expensive, and like was said before, not ever 100% reliable when it comes to spectacular failures, but we're well over the "good enough" point for mass scale EV adoption, whether it's a Tesla or a city scooter.

[Connecteur]

People really overstate the durability of current-gen lithium ion cells. What really sold me on battery aging was to see the chart of capacity loss versus (change in) internal resistance

Do they? This is a solved problem, call your 80% "100%", and 20% "0%", just like they do in real EVs that have been out for >10years, and you don't loose appreciable capacity over the lifetime of the vehicle. People just need to collectively pull their heads out of their asses and actually engineer something. It's hard, expensive, and like was said before, not ever 100% reliable when it comes to spectacular failures, but we're well over the "good enough" point for mass scale EV adoption, whether it's a Tesla or a city scooter.

My Prius Plug-in is ten years old, and it still holds nearly the same charge it did when it was new.  I read somewhere that the EV battery is charged to 70% capacity when full, and drains to 40% when considered depleted.  I applaud this type of engineering; in contrast to my Samsung phone, which overcharges to 4.4 volts, clearly intended to make it fail sooner.  I got less than two years out of the battery before it swelled and popped open the case.

[Connecteur]

When your livelihood depends on selling new parts, it's not surprising that the advice often points in that direction.

Sorry but I call BS. When each cell is like a little flamethrower, you'd think twice before screwing around with it. Maybe try doing some destructive tests on say pouch cells, and hopefully gain some respect for it. When one tiny pouch cell is capable of giving you 3rd degree burns over a large area of your body, it's no longer about "overconsumption". And for the record, my livelihood has nothing to do with selling lithium cells, but I've seen enough (in a professional mass production context, I can't imagine how much worse shitty hobby RC stuff is) to know that when it goes bad, it goes bad.

I respectfully disagree.  I've been experimenting with Lithium batteries for decades, and they are not "flamethrowers."  They are quite safe, and require a lot of abuse and dumb luck to make them catch fire.

[Connecteur]

My first experience with this technique was a great success.  My Dyson hand vacuum was working for shorter and shorter runtimes, until it became unusable.  I put the battery in a freezer bag and left it in the freezer overnight. The next day, I put it back in the vacuum and hung it up in the charger cradle.  I did a run test and it ran continuously for over 7 minutes.  Not bad considering that the manufacturer claimed a 9 minute run time.

[f4eru]

People really overstate the durability of current-gen lithium ion cells.

Nope.
People really fail to understand the role of temperature and charge management in the durability of cells.
Modern EV batteries with liquid cooling and proper management outlive the car with a factor 2-5x

10 Years ago, the question was : "What do we do with the EV when the battery is worn ?"
Today, the question is : "What do we do with the Battery when the EV is worn ?"

[Siwastaja]

People really overstate the durability of current-gen lithium ion cells. What really sold me on battery aging was to see the chart of capacity loss versus (change in) internal resistance (https://ssj3gohan.tweakblogs.net/blog/18181/how-to-manage-a-battery). Every 10% loss of capacity, starting from 88%, roughly corresponds to a doubling of internal resistance. At 50 or 60% capacity, it may be the case that half of the energy you put into charging the cell goes to heat, and the same happens in reverse. A 25% efficient battery is better allocated to the smelter to make new batteries.

But in many applications, doubling of internal resistance does not matter at all. It does matter with power tools and such, and to some degree with electric vehicles if they are driven aggressively. But many applications are like C/5 or C/10, and then it's fine if a originally 1C-capable cell becomes just 0.5C capable.

Increasing R does not limit efficiency, lim eff when (current->0) is always very close to 100%. It just means that whatever is considered acceptable efficiency is achieved at lower current than before. This needs to be considered in second life and long-term applications.

[uer166]

When your livelihood depends on selling new parts, it's not surprising that the advice often points in that direction.

I respectfully disagree.  I've been experimenting with Lithium batteries for decades, and they are not "flamethrowers."  They are quite safe, and require a lot of abuse and dumb luck to make them catch fire.

The issue is that if that's based on personal experience only, you have no idea of the real risks involved. There's not enough data from one person's experiments to say one way or another. It's like taking in a cup of water from the ocean and proclaiming that there is no fish out there.

In reality, after you ship a few million cells, you'll realize that some cells are flamethrowers without any discernible root cause. Some are flamethrowers due to unexpected use and edge cases that weren't accounted in the design, and quite a few are flamethrowers due to idiot users who don't respect the technology at all.

I've seen burned down cars in garages, house fires, vehicles just spewing out fire out of the pressure vents. In one case some dumb-ass left a hobby-grade RC unprotected pack in his EV while it was charging in his garage, and that pack started a fire. Guess what was blamed? The EV and the charger.

It's tiring to see people fuck around with this, eventually find out from personal experience, and pull a surprise Pikachu face with a "but it's never happened before, so it must not be my fault". Feel free to ignore all the data that is available and learn from your own mistakes instead of other people's.