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Thread: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

  1. #1
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    Default How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    As posted above, do most lithium ion batteries just have a shorter run time, simply not hold a charge or something else?
    Last edited by JAS; 08-06-2020 at 07:52 AM.

  2. #2

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    mAh capacity declining is the easiest symptom to benchmark, 70-80% is a good EoL definition, for most LI chemistries

    which get much more prone to thermal runaway, boom bad.

    IR rising a bit trickier.

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    *Flashaholic* ChrisGarrett's Avatar
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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Quote Originally Posted by john61ct View Post
    mAh capacity declining is the easiest symptom to benchmark, 70-80% is a good EoL definition, for most LI chemistries

    which get much more prone to thermal runaway, boom bad.

    IR rising a bit trickier.
    Thermal runaway is now mostly a thing of the past, with the discontinuation of true lithium-cobalt chemistries.

    You're correct in stating rising I.R.s and lower capacities, as being signs of a declining cell.

    And then it was mostly an issue of 'charging' cells back up that were stored near zero volts, where copper dendrites could form.

    Not saying that modern cells can't get to a thermal runaway point, but it's not much an issue with modern cells and chemistries.

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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Not **as** easy to do

    is far from "now safe".

    False sense of security actually increases the risk for noobs.

    With bigger like RC sized packs fires regularly burns houses down.

    It's knowing what you're doing that reduces to risk.

    And using LFP or LTO if you don't really need the high energy density of the 3.6-3.7V chemistries

  5. #5

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    I would like to point out from first hand experience is while they are charging, they start to get warm at the cv phase as current starts to dip.

    Sometimes it does not terminate and just stays red longer than it should on one of the cells while temp slowly keeps going up.

    The weird thing though, is that it will terminate sometimes on that cell in question. Even put a piece of tape to mark it.
    Last edited by MarioJP; 08-07-2020 at 08:55 AM.

  6. #6
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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Quote Originally Posted by MarioJP View Post
    I would like to point out from first hand experience is while they are charging, they start to get warm at the cv phase as current starts to dip.

    Sometimes it does not terminate and just stays red longer than it should on one of the cells while temp slowly keeps going up.

    The weird thing though, is that it will terminate sometimes on that cell in question. Even put a piece of tape to mark it.
    That's normal for worn-out cells.

    The reason is that the cell can not hold a full 4.20v charge anymore. It might have a resting voltage closer to 4.05v (for example). So, when the charger attempts to fill it further than 4.05v, a lot of the charge is lost to heat as the cell has difficulty retaining that charge.

    You'll find that it takes a very long time for the charge to complete at 4.20v. The charger goes into the CV phase, and it just keeps dumping in a small amount of current (say 100mA), while the cell is shedding most of that into heat as it tries to self-discharge. Eventually, the charger may get close enough (it has a pre-determined CV current where it will cut off), that it marks the cells as full and stops charging. Or, it may never get there.

    If you measure the cell voltage after charging, you'll notice it has fallen down to 4.10v or lower, after just a few minutes.

    Anyway, the point is that worn-out cells don't hold much capacity, they don't hold a full charge, and they have awful internal resistance.

  7. #7

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    For better longevity with these chemistries better to charge Bulk/CC only and stop at 4.05V starting from when they are brand new anyway, maybe 4.1V

    Going all the way to 4.2V, much less holding any CV is very stressful and reduces lifecycles a fair bit.

    Most only last a couple hundred cycles anyway, especially at high C-rates.

    Using such cells past their EoL point really increases the risk of thermal runaway,

    Boom Bad!

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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Quote Originally Posted by john61ct View Post
    Using such cells past their EoL point really increases the risk of thermal runaway,

    Boom Bad!
    Well, I'm not sure there's any evidence of that. Maybe if you're trying to drive them at a constant 20 amps under a regulated driver. But I'd worry more about thermal runaway in new cells if you're doing that, as they probably can run for a lot longer which gives time for internal heat to build up.

    Generally, worn-out cells just have such poor performance, that they're not worth using. Throw them away, and buy new ones.

    If you notice they have self-discharge, regardless of the resting voltage level, then throw them away faster. They have developed an internal short.

  9. #9

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    The most dangerous time for LI batteries "exploding" is while charging not discharging.

    There are hundreds of events recorded as evidence of this danger

    not saying the use cases represented in this website are especially risky nor safer.

    If you're starting with quality new cells and routinely recycling them as their capacity loss becomes evident

    then that is likely to prevent any such problems.

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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Again, I'm not aware of any evidence that shows worn-out lithium-ion cells are any more dangerous than new lithium-ion cells. If you abuse either one, you risk them venting, catching fire, or even exploding. However, a new lithium-ion cell can store a lot more energy than a worn-out cell, so the risk is even greater, IMO.

    The reason to buy new cells is not for safety, but because old cells have poor performance.

    That said, old cells can develop internal shorts, and you need to watch out for that because it is a safety concern. However, I have had 3 new cells develop internal shorts, and they only had about a dozen cycles on them. So, it's not a problem specific to old cells.

    And yes, when charging, you need to be careful, with all cells.

  11. #11

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Good points, surprisingly though, they are still good at charging my phone from low to full even with reduced capacity. But i do notice that the battery% on the power bank does drop easily when charging a device. By the time it fully charges the device, the power bank went from 100% to around 50-45% on a single use. I currently using 4 NCR18650B for my power bank. These cells are at least 4 years now.

    I have reduced the charging speed to 500mA and set to terminate when it hits 200mA at 4.20v Sometimes i just don't use the external charger and have the power bank charge them.

    Before, i used to have it terminate at 60mA. This charger allows you to set the termination as low as 0. I know that can't def be good for the battery for a perfect top-off charge lol. That's just unrealistic to be honest.
    Last edited by MarioJP; 08-07-2020 at 11:04 PM.

  12. #12

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Generally speaking, the IR rises, and the capacity declines. The capacity curve is similar to the discharging curve in that there is a "knee" where it's very flat, but after that it starts to drop faster and faster.
    Here are some values from my laptop where I went through a complete battery until it reached about 50% of its original capacity, and before that...
    on the first cycle it had 105% of it's rated capacity,
    Cycle 12 yielded 102%,
    Cycle 58 yielded 97%,
    Cycle 125 yielded 95%,
    Cycle 236 yielded 93%,
    Cycle 313 yielded 91%,
    Cycle 402 yielded 85%,
    Cycle 456 yielded 75%,
    Cycle 537 yielded 66%,
    and Cycle 580 yielded 50%, after which the battery was retired.

    On Cycle 537, the IR also was abut 2.5 times as high as with the fresh cells.

    As you can see, the curve was very flat between cycles 125 and 313 and started to drop more and more sharply after that. That was, however, a battery bought in early 2012 and used util late 2016, which has been a few years now, so your results may vary...

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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    This is pretty much how my lithium batteries are, at the end: 59 seconds

    https://youtu.be/BJuCv0glTG0

  14. #14

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Quote Originally Posted by WalkIntoTheLight View Post
    Again, I'm not aware of any evidence that shows worn-out lithium-ion cells are any more dangerous than new lithium-ion cells.
    That is simply a limitation of your knowledge and exposure, there is no doubt it is most definitely the case.

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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Quote Originally Posted by john61ct View Post
    That is simply a limitation of your knowledge and exposure, there is no doubt it is most definitely the case.
    Okay, seeing as you're so knowledgeable, cite the evidence.

  16. #16

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Quote Originally Posted by WalkIntoTheLight View Post
    Okay, seeing as you're so knowledgeable, cite the evidence.
    He *is* correct. You *are not*.

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    *Flashaholic* ChrisGarrett's Avatar
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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Gauss163? Gauss163 to the white courtesy phone.

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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Quote Originally Posted by skid00skid00 View Post
    He *is* correct. You *are not*.
    Wow, okay. I guess that settles it then. No evidence needed, just an opinion. Welcome to the Internet, I guess.

  19. #19
    Flashaholic* Stoneking's Avatar
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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    I can’t find any articles stating worn or aging cells are more dangerous.
    I would be interested in some form of study or proof of this.
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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    I was part of the original group of CPF'ers that were amongst the world's first use of lithium ion cells in flashlights. lots of explosions back then starting out when very little was known about then emerging technologies for individual use of li-ion cells.

    have been using those same batch of early lithium cobalt cells since then. it makes a huge difference for safety and longevity related to which li-ion charger you are using.

    what I've noticed over a decade+ of using those early li-ion cells is .. lithium cobalt cells will first start losing it's ability to hold a charge. for instance after cell reaches and/or attempts to reach 4.2v during charge cycle, charger will then indicate cell actually is holding say 90% or whatever. then cell in following charge cycles will start holding less and less .. followed by cell failing to hold a charge at all.

    above is for early lithium cobalt cells charged individually with a state of the art li-ion charger in a clamp mod mentioned in sig. over the years I've upgraded li-ion chargers/power supplies especially as different chemistries emerged.

    please note my preference for quite sometime when using lithium cobalt cells .. is to use flashlights that allows single cell configuration. Amazing how far lithium technologies has progressed.

  21. #21

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Quote Originally Posted by Stoneking View Post
    I can’t find any articles stating worn or aging cells are more dangerous.
    I would be interested in some form of study or proof of this.
    I have no study nor proof, but some solid theories how worn or aging cells might be more dangerous...
    1. The rising IR causes the cell to heat up more and more under the same load. If it gets too hot, it might go into thermal runaway, which a new cell would not do under the same load.
    2. If used together with other cells, at least badly done battery packs might slowly fall out of balance, which might cause some cells to get too high or low in charge, which is dangerous as well.

  22. #22
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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Quote Originally Posted by Kurt_Woloch View Post
    The rising IR causes the cell to heat up more and more under the same load. If it gets too hot, it might go into thermal runaway, which a new cell would not do under the same load.
    The chance of thermal runaway, and the amount of damage that would do, is directly proportional to the energy contents of a cell. Old / worn Li-ion cells have lowered capacity, can't deliver high currents anymore, and for those reasons alone they're less dangerous. Just go watch some YouTube videos of Li-ion cells blowing up: almost without exception, you'll see energy being fed into the cell as it happens (12V car battery wired to 3.7V Li-ion cell etc). Fully charged cell on its own (perhaps overcharged) - hmm not so much. Maybe if short-circuited or punctured with a nail. Perhaps if you take enough high-capacity cells & wire them the wrong way. Worn out / old cell: not happening, energy contents does not suffice to provide fireworks that are worth the effort.

    If you think otherwise then please provide some pointers otherwise stop scaring people with a non-issue.

    Of course the higher IR of old Li-ion will limit its usefulness. There is nothing 'tricky' about that: apply intended load. Fresh cell will have no problem. Old cell with good remaining capacity but increased IR won't be able to handle it. Old cell with decent IR but lower capacity won't handle it either. End result is the same: cell unfit for purpose. And it doesn't matter much whether it's due to capacity loss, higher IR, or some combination thereof.

    Likewise when selecting cells I don't care what % remaining capacity is of rated capacity for a new cell of that type. I just apply a load that reflects common usage for me, and performance (capacity) at that load is what counts. Can't handle that load? Out! To little capacity @ that load? Out! The rest can stay. Specifications or brand are interesting, but don't decide whether a cell is kept or not.

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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    I am unaware of any public studies as well. There would be a need to separate and compare the differences of the many different chemistries available.
    There have been posts/articles over the years of damaged cells causing troubles, especially in multi cell configurations.
    Posts on accidentally mixing in a discharged cell in a multi cell light has led to incidents.
    Many Manufacturers that sell these cells limit their warranty period to 12 months or less.
    IMO, the quality of the cell along with the care, usage, and the type of charging will influence it's useful life span.
    I have cells that are 5 years old that work fine, and I've retired cells with ~20 cycles on them.

    I dissected a Makita 18V power pack that the charger would not charge. One of the cells only had 1.3V the rest were above 3.7.
    I found the same thing on an old laptop battery pack. I still have a few laptop cells that work fine. Unbalanced multi battery configurations
    can cause an un-safe condition. This is why they won't charge, the difference between cells is too great and the charger shuts the pack down.

  24. #24
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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    My (not an expert) understanding is that many of these chemistries are affected by dendrites.

    These tend to form especially under conditions of low SoC. Once formed, they tend to grow over time.

    The highest capacity (when new) cells, meaning the more and/or thinner layers in the cell, tend to be at the highest risk of damage from dendritic growth.
    ... is the archimedes peak

  25. #25
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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    most of the cells that I EDC .. currently li14430 or CR2 size, all 10+ years old
    what I've noticed is .. as cells age charger when set to 1C tend to draw way more than 1C amount of amps and/or milliamps.

    for instance .. charger set to 1C results in cell being charged hard enough to heat up cell or not good. so instead of charging at 1C .. I'll set charge rate to 600 milliamps or what ever.

    this is assuming one has a charger with settings. not everyone has a state of the art charger. years back I realized the greatest danger from using li-ion cells occurs during charging. hence justification to spend extra $$$ for extra safety factor.

    just so happens that accurately charging lithium cobalt cells appears to extend life as well.

  26. #26
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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Quote Originally Posted by cy View Post
    most of the cells that I EDC .. currently li14430 or CR2 size, all 10+ years old
    what I've noticed is .. as cells age charger when set to 1C tend to draw way more than 1C amount of amps and/or milliamps.

    for instance .. charger set to 1C results in cell being charged hard enough to heat up cell or not good. so instead of charging at 1C .. I'll set charge rate to 600 milliamps or what ever.
    I generally charge all my 18650's at 1 amp. It's a good compromise rate; doesn't take forever, nor does it stress the cells.

    I notice that on some very old laptop cells, which are rated for only 1.1 amp charging (when they were new), they don't overheat with 1 amp. However, the charger very quickly will go from the CC phase, into the CV phase. This decreases the charging current by design, and a good chunk of the charge will happen in that CV phase. That's because the high internal resistance requires more voltage to charge.

    On a high-drain new cell, almost all the charge comes from the CC phase, because the low internal resistance doesn't require much voltage differential to charge it.

    Anyway, my point is that if you charge at a reasonable rate, I wouldn't worry too much about whether the cell is old or new. A good charger will adjust. Of course, always feel the cell occasionally to make sure it's not hot. If it is, something might be wrong and presenting a safety issue.

    Oh, and there's plenty of dangerous cheap chargers on the market. So, make sure you buy a known brand that makes good chargers.

  27. #27

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Hey guys,

    I have to give thanks for this thread that made me realize that when it is time to replace the cells lol. I have one particular cell that starts to heat up even at 500mA charge rate.

    This cell has reached 45c temp and luckily the charger safety features kicked in as it was flashing red. This cell was quite hot.

    Any idea why this cell heats up like that? I noticed the heating up starts when the cell hits around 4 volts, not even close to hitting 4.1 yet.

    I finally ordered replacement cells which are 18650GA an upgrade from NCRB's i suppose. Not liking how this cell heats up and it is making me nervous lol.

    Any idea what's going on internally with this cell?

    Thanks.
    Last edited by MarioJP; 08-19-2020 at 09:03 AM.

  28. #28

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    growth of dendrites causing internal shorting

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    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    Any cell that heats up to the point You can't touch it >125° is bad.

    There also could be subsiquent damage to the cells insulating layers from the excess heat further accelerating the decay.
    Do this Take the Voltage of that cell. You said You charged it previous to ~3.9-4.0V?. Let the cell sit for a week and test the voltage again. I wouldn't be surprised if it were close to or below 3.5V. This test verifies that the cell does need to be retired.

  30. #30

    Default Re: How Do Most Lithium Ion Batteries Behave When They Are Approaching End Of Life?

    One week later, this cell in question remains at 4.12v (end charge termination was a bit high when cell was charged) But one thing is clear, when together with the other cells.

    This is the only cell out of the 3 that has far less capacity and voltage jumps higher when charging and drops futher down when discharging than the rest of the cell group.

    At first, i thought this cell had more charge than the rest, so what i did is discharged them all down to 3.00v equally. Did a slow charge and fair enough, the voltage in this particular cell kind of jump a bit higher than the rest after 5 min or so.

    Sometimes it can be off by .10v from the other 3. So yes, one week later, cell remains at 4.12v while the other 3 remained at 4.15v

    So does not look like it is a short, but i think this cell is nearing end of service much sooner than the other 3 due to abnormally heating up during charging even at low currents.


    Just out of curiosity out of this thread, anymore ideas as to why this cell is giving out sooner than the rest? They were all used equally in a power bank.

    Luckily the cells are in parallel configuration, so that's good at least.

    Strange behaviour from li-ions lol.
    Last edited by MarioJP; 08-27-2020 at 09:31 PM.

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