Author Topic: Don't keep fully charged Li-Ion in long term storage, they tend to bulge  (Read 7508 times)

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Offline Miti

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #25 on: January 14, 2023, 12:52:09 pm »
Would it be a bad idea to charge a Li-Ion very slow, for 3-5 days non-stop using CC-CV?

Nope, nothing wrong with that but don’t trickle charge it. Once it is fully changed, stop, let it discharge a bit. A dedicated chip would do just that.

Edit: 3-5 days seems excessive for me. Take a look at Microchip MCP73831 for single cell. It can deliver up to 500mA in an SOT23 package. A good battery should not heat up while charging at below 1C so 5-10 hours should be reasonable.
« Last Edit: January 14, 2023, 01:05:03 pm by Miti »
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Offline Siwastaja

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #26 on: January 14, 2023, 02:24:27 pm »
There is no lower limit for charging current.

You can even connect it permanently to a CC-CV supply, even if some manufacturers do not want to support such operation mode. Usually they are just unclear about it and people jump to conclusions.

Timeouts are recommended as some kind of extra safety layer but that is very ineffective, nearly total false sense of security.
 

Offline james_s

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #27 on: January 14, 2023, 08:42:29 pm »
I just found some old Varta Li-Po batteries in a pile of junk at work after an inventory cleanup. Brand new, never used but made in 2009. They all measure zero volts at the output of the protection board, the battery itself between 2.2 and 2.3V. They are small 300mAh. I fully changed one and checked its capacity down to 3V at 50mA and at 100mA. The result in both cases was around 350mAh. Not bad for a 22yo battery.
I wouldn’t normally recharge a big battery that discharged this low, but at this size I don’t think there’s any risk.

There's some funny math going on there, I calculate 13 years old, not 22, and I'm wondering if you got the capacities backwards because you measured higher than rated capacity? That's still a good bit of time.
 

Offline Miti

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #28 on: January 15, 2023, 12:16:10 am »
There's some funny math going on there, I calculate 13 years old, not 22, and I'm wondering if you got the capacities backwards because you measured higher than rated capacity? That's still a good bit of time.

 :palm: Yes, 13 - 14 years. I don’t know how I calculated.
I use an electronic load to check the capacity, I can’t get it wrong. In general, a good brand name such as Varta, gives the minimum capacity so is not uncommon to measure higher than specs.
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Online tom66

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #29 on: January 15, 2023, 12:20:08 am »
I've got some old Canon DSLR 7.4V Li-Ions for my very old EOS 20D (it really is due an upgrade, but it was a hand-me-down from my father and it still works.)  IIRC they were rated for 1,000 photos each, and they easily did that despite being 10 years old.  The risk of Li-Ions dying quickly I think is overstated.   If they're even reasonably well treated they can last a decade or more.
 

Offline james_s

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #30 on: January 15, 2023, 12:23:45 am »
I don't think they are known for dying quickly if they are treated reasonably, but they have a low tolerance for abuse. I still have numerous LiPo packs that are going on 9 years old now that have hundreds of flights on them and still perform well. I have always been diligent about putting them at a storage charge and I normally store them in the refrigerator over the winter when I'm not flying.
 

Offline RoGeorgeTopic starter

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #31 on: January 15, 2023, 09:46:55 am »
From personal experience, Li-Ion have the longest life from all domestic batteries.

- Pb acid batteries, wet or gel (thinking car batteries and UPS batteries) last 5-10 years most.
- NiCd or NiMH (AA or AAA) about 2-5 years, after that the internal resistance grows and make them unusable (for NiMH), while most of my NiCd grown internal short-circuits.  The shorted ones can be pulsed with huge current to burn the internal short-circuits (put a 1.2V cell in parallel with a 12V car battery for a second or so to fuse any internal wiskas), but a couple of days or weeks later they will self-short again.
- Li-Ion can live 10-15 years maybe more, judging by the batteries from the 90's mobile phones that are still working today.  Even the inflated ones still keep 50-70% of their nominal capacity.

The only ones I know to last even longer are some open batteries I've seen in industrial environments, but those used to have their own dedicate room and have been constantly checked/refilled by qualified personnel.  Seen such battery rooms as backup for telephone exchange centers or for control equipment in energy distribution stations near power plants.  One of those battery rooms was 50+ years old and all the cells were still working fine.

Online Psi

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #32 on: January 15, 2023, 09:54:51 am »
Often they store them at a voltage that's higher than the "ideal" storage voltage because all cells will self-discharge some percent per month.
Usually 1-2% but it can be higher if the cell has a PCM (like 3-5%).

So it's a trade off. If you charge them a bit higher they will last longer before self discharge takes them so low that damage may occur from undercharge.

So you kinda have to decide, do you want to cause a little damage now to prolong their storage lifespan.
It really depends how long you plan to store them for.

IMHO as long as you store them under 4V it's pretty safe.
So for long term storage I use 3.85-3.90V
Short term storage I use 3.75V-3.80V

It does depend on the chemistry though,  cells designed for very rapid and high discharge are more prone to damage if left fully charged than cells intended for slow discharge.
« Last Edit: January 15, 2023, 10:05:52 am by Psi »
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Offline Siwastaja

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #33 on: January 15, 2023, 10:05:23 am »
Often they store them at a voltage that's higher than the "ideal" storage voltage because all cells will self-discharge some percent per month.
Usually 1-2%

Usually much less than that. If you actually measure, that is, instead of reading Battery University or internet forums. But yeah, some cell might just self-discharge by 1-2%/month at 80-100% SOC, at 45degC or something like that.

(I have posted some data in https://www.eevblog.com/forum/chat/lithium-ion-battery-degeneration/msg3217888/#msg3217888 )

Quote
So it's a trade off. If you charge them a bit higher they will last longer before self discharge takes them so low that damage may occur form undercharge.

Bullshit. Self-discharge nearly stops at SoC < 50%. If "self-discharge" brings a cell to death via overdischarge (copper dissolution), then it was a very crappy cell. If the cell has internal damage from e.g. earlier overdischarge, then sure this happens, but it also offers a good checkpoint to report broken cell to the user, by refusing to charge.

Does not happen with decent cells.

Now faulty or poorly designed protection modules can consume whatever current. 3-5% of capacity discharged per month is not IMHO acceptable, it's an order of magnitude too much. But for some users / applications, it might be OK. Lazy BMS designers designing packs that self-destruct by misunderstanding the actual field requirements (and assuming large self-discharge is OK) are the plague of the BMS industry, though.
« Last Edit: January 15, 2023, 10:07:14 am by Siwastaja »
 
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Online Psi

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #34 on: January 15, 2023, 10:12:39 am »
Bullshit. Self-discharge nearly stops at SoC < 50%. If "self-discharge" brings a cell to death via overdischarge (copper dissolution), then it was a very crappy cell.

You can't use the argument "good cells don't do that so you're wrong" when there's loads of crap cells people have to deal with.
Not everyone gets to play with the top tier cells.
Lots of consumer stuff has shit cells with shit PCMs because they are cheap and cause planned obsolescence.
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Offline Siwastaja

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #35 on: January 15, 2023, 10:17:47 am »
I can use whatever arguments I want :).

I'm not talking about "top tier" cells. I'm saying if a cell dies on its own due to self-discharge bringing it from 30% to zero, it's total crap. Possibly dangerous. Use at your own risk, and if weird tricks are needed to keep it "alive", this information is not useful to generalize.

Besides, charging it to 70% won't help. If it self-discharges that much at 30%, it self-discharges even more at 70%, so it gets to 30% and then 0% quickly anyway. You would need to keep the cell in a charger all the time, and that would make it even more dangerous.

Now a broken-by-design protection module could be nearly constant current drain, so using e.g. 80% instead of 40% would double the "time-to-death". I still don't know if it's worth anything. 30% is massive amount of charge to lose. Trying to work around a protection module which loses 3% per month is like using duct tape to keep your steering wheel from falling off in a car. (mandatory car analogy). Or use bubble gum to fix a hole in gasoline tank, I did that once in my car and guess what, I had to repair it properly the next day anyway.
« Last Edit: January 15, 2023, 10:21:32 am by Siwastaja »
 

Online magic

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #36 on: January 15, 2023, 12:03:01 pm »
Is there any "quick and dirty" way to put a battery into a reasonably safe long term storage level without coulomb counting?
Like, say, (dis)charge to 3.6V or 3.8V or something of that sort.
 

Offline Siwastaja

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #37 on: January 15, 2023, 01:08:31 pm »
Is there any "quick and dirty" way to put a battery into a reasonably safe long term storage level without coulomb counting?
Like, say, (dis)charge to 3.6V or 3.8V or something of that sort.

Anything between about 3.55V and 3.7V is nearly optimal. 3.8V is fine, too, but don't go much over that or you'll start losing the advantages in calendar fading. People assume storing at 4.0V is already significantly better than at 4.2V, but depending on cell, the difference can be small.

Remember, if you use large discharge current, terminal voltage = OCV + ESR * I, where OCV = open circuit voltage, which you try to get within your optimum range. So, maybe simply discharge down to say 3.55V and let the voltage bounce back to 3.6V or 3.7V or whatever; it's good enough.
 
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Offline BravoV

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #38 on: January 15, 2023, 01:18:07 pm »
Alternative view, on storing Li-Ion cell, the sweet spot is 4.03 volt, the longer the cell is soaked in higher voltage, say like 4.15 volt, the faster the decay.

At least according to Jeff Dahn at below video is at 4.03 volt ... approx. about 80%, and gets worst above 4.1 volt. He is well known expert in battery, currently working with Tesla in battery development.

You can search who Jeff Dahn is, in the net.

I marked youtube link below right at the time at 1h07m, in this Youtube video where its discussed this particular issue ...

-> https://youtu.be/pxP0Cu00sZs?t=1h7m5s

Even though its a 1 hour 14 mins video length, recommending to watch this Prof. Jeff Dahn video from the beginning, its very informative, imo.
 
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Offline Siwastaja

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #39 on: January 15, 2023, 01:24:53 pm »
Alternative view, on storing Li-Ion cell, the sweet spot is 4.03 volt, the longer the cell is soaked in higher voltage, say like 4.15 volt, the faster the decay.

As always, "alternative views" tend to be wrong.

You can refer to the measured data on Samsung 29E cell posted by me for example in this thread:
https://www.eevblog.com/forum/chat/lithium-ion-battery-degeneration/msg3217888/#msg3217888

I also remember a paper where a Panasonic cell faded MORE quickly at around 4.0V than fully charged. I haven't replicated this of course and don't remember the authors/title.

But sure, some particular cell type, possibly something used at Tesla, can already show calendar fading down to negligible values at 4.03V, and it's obviously a pretty good feature for a cell. For example, in my dataset of two cells, one (Samsung 26H) was that way. Just don't generalize it and assume all cells show significant calendar life improvements at 4.0V.
« Last Edit: January 15, 2023, 01:27:06 pm by Siwastaja »
 

Online tom66

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #40 on: January 15, 2023, 01:27:04 pm »
There's a reason Tesla, VW, Polestar, and MG all have a recommended 80% charging limit, with the 100% being reserved for road trips. If you keep an EV battery between 80% and 0% (there's little disadvantage to going to the low state of charge) then the battery will last a really long time.
 

Offline Siwastaja

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #41 on: January 15, 2023, 01:29:20 pm »
There's a reason Tesla, VW, Polestar, and MG all have a recommended 80% charging limit, with the 100% being reserved for road trips. If you keep an EV battery between 80% and 0% (there's little disadvantage to going to the low state of charge) then the battery will last a really long time.

According to my tests, it's the cycling damage which is pretty significant between 80% and 100%; especially at higher currents and lower temperatures. This is the region of lithium plating. Calendar fading component depends a lot on the cell, some are much better at 80%, some are not. But cycling damage component is always better when you stop at 80%, so that's a reason alone to do it.

This is also why I'm a little bit naysayer when it comes to this "boohoo, follow the manufacturer instructions and continuously cycle the cell between 100% and 80% instead of CC-CV float charging at 80%" stuff we occasionally discuss, and recommend floating at 4.0V instad.
 
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Offline BravoV

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #42 on: January 15, 2023, 01:49:10 pm »
Alternative view, on storing Li-Ion cell, the sweet spot is 4.03 volt, the longer the cell is soaked in higher voltage, say like 4.15 volt, the faster the decay.

As always, "alternative views" tend to be wrong.


According to an "anonymous" source in some public forum, compared to Prof. Dahn, yeah, right.  :-DD

Offline Siwastaja

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #43 on: January 15, 2023, 02:40:36 pm »
According to an "anonymous" source in some public forum, compared to Prof. Dahn, yeah, right.  :-DD

Read and try to understand what is said, instead of who is saying that. Usually there is no contradiction at all, you are just being confrontative for no reason. Only when there is contradiction, then you might want to apply "appeal to authority" - but be careful; see the "Nobel disease" phenomenon for example. For on-topic example about li-ion, John B. Goodenough, called the inventor of lithium ion, have caused embarrassed reactions within the industry in his old days.

With appeal to authority, you sometimes win the internet argument, but you can't win the understanding to the subject that way.

In this particular case, Prof. Dahn is apparently (I did not check) saying a li-ion cell used by Tesla shows significant calendar fading improvement when stored at 4.0V, and engineer A. Alhonen (me) says that during his testing, Samsung ICR18650-26H did show significant improvement at 4.0V, but the newer Samsung INR18650-29E did not. There is absolutely no contradiction as I see it.

« Last Edit: January 15, 2023, 02:45:49 pm by Siwastaja »
 

Offline RoGeorgeTopic starter

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #44 on: January 15, 2023, 02:50:44 pm »
Is there any "quick and dirty" way to put a battery into a reasonably safe long term storage level without coulomb counting?
Like, say, (dis)charge to 3.6V or 3.8V or something of that sort.

That's what I come with, because I have plenty of DZ4V3 (NOS), and power LEDs with radiator (from bad light bulbs :D):



Either charges or discharges until the battery reaches 3.7V, the Li-Ion cell is ready for long term storage when the two LEDs light at about the same intensity.  Main goal was to keep the currents small enough so any small battery can take that (50mA when charging, 20mA when discharging).
« Last Edit: January 15, 2023, 02:55:14 pm by RoGeorge »
 

Offline james_s

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #45 on: January 15, 2023, 07:16:07 pm »
- NiCd or NiMH (AA or AAA) about 2-5 years, after that the internal resistance grows and make them unusable (for NiMH), while most of my NiCd grown internal short-circuits. 

They should last longer than that. I started buying Eneloop NiMH batteries not long after they came out, must have been 2006-2007. I just recently had a few of my oldest ones fail and really they're still usable for some applications, just the capacity dropped from 2000mAh down to ~1500mAh so I marked them and will use them in TV remotes and such.
 

Online thm_w

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #46 on: January 16, 2023, 11:38:10 pm »
- NiCd or NiMH (AA or AAA) about 2-5 years, after that the internal resistance grows and make them unusable (for NiMH), while most of my NiCd grown internal short-circuits. 

They should last longer than that. I started buying Eneloop NiMH batteries not long after they came out, must have been 2006-2007. I just recently had a few of my oldest ones fail and really they're still usable for some applications, just the capacity dropped from 2000mAh down to ~1500mAh so I marked them and will use them in TV remotes and such.

A large percentage of the non Eneloop nimh batteries don't last long at all. Many people don't know to only buy Eneloop, and its often not available in local stores, or if it is, cost is high. Not to mention, Eneloop does not manufacture C or D cells at all.
Even within Eneloop, people have reported the China manufactured cells are not nearly as good. And that has been shown to be true at high discharge: https://www.candlepowerforums.com/threads/japanese-vs-chinese-eneloop-cycle-testing-results.392229/

So, it is very easy to buy the "wrong" nimh that dies after <5 years.
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Offline RoGeorgeTopic starter

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #47 on: January 17, 2023, 11:38:38 am »
In EU there are other brands.  I don't recall seeing Eneloop other than on the Internet, they seem to be the preferred brand in US at least.  Maybe I should buy some Eneloop to test them, too.

So far all my NiMH were not that good.  Have tried many brands for a photo camera that uses 4xAA.  Tried so far GP, SONY, VARTA, DURACELL, UNiROSS, no name, etc.  All failed after 2-3 years.  The upper left bowl is full of failed AA.



Most common failure was high internal resistance.  In the camera they were good to deliver only small currents to take normal pics, but not able to deliver high current to charge the flash.

Since LIDL supermarket became a thing here, in Ro, they came with a new brand of NiMH, "TRONIC", advertised as "low self discharge".  They are indeed low discharge and seems very good for the price (about $1 per AA cell), size from AAA to C size and 9V too.

They last about the same, 2-3 years.  After that, they are good only for low current loads.  I've made a discharger for AA some years ago, and many of the old AA were not able to deliver the usual 0.2C current.  Voltage was dropping under 0.9-1V at 0.2C, though at about 10 times less current they were still able to deliver 50-80% of their nominal C.


Offline RoGeorgeTopic starter

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #48 on: January 17, 2023, 11:58:48 am »
Checked out of curiosity, Eneloop is available in EU, too, just that they are 3-4 times more expensive than the TRONIC ones from the LIDL supermarket.
https://www.emag.ro/brands/brand/eneloop

Offline MadScientist

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Re: Don't keep fully charged Li-Ion in long term storage, they tend to bulge
« Reply #49 on: January 17, 2023, 05:38:37 pm »
Very low charge rates should be avoided , ie below 0.2 C as  very low  charging rates encourages SEI layer growth and hence leads to battery degradation.  Chargers at 0.5c then stop charging once full no float etc needed. Track SOC band restart charging at a point

Long term storage is best at 60-70 % SOC but really fine upto 80% SOC avoid very low Soc for storage or below 40% SOC

In essence short high current charge ( relatively high ) is best once the correct safety regime and a proper stop charge point is set
« Last Edit: January 17, 2023, 05:42:31 pm by MadScientist »
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