Don't keep fully charged Li-Ion in long term storage, they tend to bulge - Page 1
Forum section: electronics / general

author: RoGeorge
author_rank: Super Contributor
timestamp: January 12, 2023, 06:22:09 pm
content: Many of the used phone-batteries (Li-Ion) left fully charged about a year ago have bulged meanwhile. I didn't know that in long term storage Li-Ion rechargeable should be half empty.Searched about this only after noticing this month how most of the old batteries decided to swollen during the last year, while they were just sitting there after they were all fully charged about a year ago. The Internet says there are some charges that even have a "storage" charging mode. None of my phones or camera chargers have such a for-storage charging mode.I'm still not sure if a fully charged Li-Ion is supposed to bulge if left fully vcharged for a long time. Though, those batteries otherwise survived without problems for 5-10 years discharged (and disconnected).Anybody else noticed storing Li-Ion fully charged will inflate the battery?

author: Infraviolet
author_rank: Super Contributor
timestamp: January 12, 2023, 08:02:59 pm
content: I always thought the trouble was if you put them in to storage nearly empty, that way they self-drain slowly and have less time before they go below the minimum voltage threshold. I had though the ideal was 75% charged, but anything in the 50% to 100% range was usually ok.

author: Gyro
author_rank: Super Contributor
timestamp: January 12, 2023, 08:21:06 pm
content: ~40% seems to be the general consensus for storage. There have been quite a few threads over the years.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 12, 2023, 08:23:21 pm
content: Whether it ends up bulging really depends on the battery. But storing one fully charged is a sure way of killing it over time. Every LiPo battery that I stored fully charged died after 2-3 years. The sweet spot for long-term storage depends. Can be anywhere from 40% to 80% SOC depending on battery and studies. Also recharge them to the storage SOC on a regular basis to avoid them getting to a dangerous low SOC by self-discharge.I have had bulging on a LiPo battery that I used as power back-up in some device. It was a 1000 mAh LiPo IIRC, and the charge current was set at 100 mA. The charging circuit would keep it fully charged at all times (only with a small hysteresis.) The bulging started after about 2 years of operation. It was pretty bad.

author: Gyro
author_rank: Super Contributor
timestamp: January 12, 2023, 09:09:30 pm
content: The Logitech Harmony One remote would keep its Lipo at 100% SOC whilst in its table tray. The battery would swell so badly that in many case, it was necessary to dismantle the remote to get the 'removeable' battery out of its slot. The FAQ said that this was normal behaviour!P.S. I still have mine. It sits on the side table and only gets charged overnight when the battery indicator shows low. The cheap replacement battery still lasts more than a week between charges, and after several years (5+ irrc), no bulging.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 12, 2023, 09:13:45 pm
content: Quote from: Gyro on January 12, 2023, 09:09:30 pmYep, not surprised. Learned it the hard way as I said above. I would never design a back-up system like this ever again.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 12, 2023, 09:19:41 pm
content: Quote from: SiliconWizard on January 12, 2023, 08:23:21 pmThe ones i have are Li-Ion, kept from former 2G or 3G mobile phones that are now out of use. Never had LiPo, heard they have to be charged while kept in an anti-explosion protective bag, though they are heavily abused in their day to day life, for example in racing remote controlled models, sumo robots and such.Are you telling about bulging LiPo because this is the type that happened to bulge from the ones you have, or because LiPo are about the same as Li-Ion?

author: thm_w
author_rank: Super Contributor
timestamp: January 12, 2023, 10:28:06 pm
content: Quote from: RoGeorge on January 12, 2023, 09:19:41 pmhttps://www.eevblog.com/forum/renewable-energy/questions-batterys-lithium/msg3582601/#msg3582601https://www.eevblog.com/forum/renewable-energy/questions-batterys-lithium/https://www.eevblog.com/forum/chat/lithium-ion-batt-storage/https://www.eevblog.com/forum/chat/lithium-ion-battery-degeneration/

author: james_s
author_rank: Super Contributor
timestamp: January 13, 2023, 01:32:14 am
content: I thought this was widely known. I've been using LiPo batteries in model airplanes since around 2014 and even then the chargers all had a storage mode to bring the batteries to around 50%. Many laptops have a battery maintenance mode that only charges them up to around 80% to extend the life.

author: thm_w
author_rank: Super Contributor
timestamp: January 13, 2023, 02:29:41 am
content: Yes its widely known, but outside of "highish-tech" hobby chargers mentioned, I've never seen consumer products that offer to charge your device to 40-60% for storage. I'm sure they exist, its just not very common.80-85% is to extend the life during regular use, and is not intended for storage or shipping purposes. And even then I'd say a lot less than 50% of products offer that.https://electronics.stackexchange.com/questions/491538/why-are-lithium-ion-batteries-stored-at-50-voltage-and-not-a-lower-voltage

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 13, 2023, 02:47:02 am
content: Quote from: thm_w on January 13, 2023, 02:29:41 amI have absolutely never seen that either, outside of, as you said, dedicated chargers. I have one in the lab that can do this and much more.But in consumer products, never seen it whatsoever.Quote from: thm_w on January 13, 2023, 02:29:41 amYep. And even 80% is too high when you keep your batteries charged for extended periods of time (say you use a laptop on AC most of the time, and only occasionally use it on battery.) That's an almost sure way of having your battery die within 2 to max 3 years. If you're lucky.

author: james_s
author_rank: Super Contributor
timestamp: January 13, 2023, 06:41:24 am
content: Yes 80% is not a storage charge. My point is only that time spent charged above about 50% causes accelerated degradation. Storing at 90% is better than storing at 100%, storing at 80% is better than storing at 90%. The ideal state of charge for maximum lifespan is around 40-50%. I've read that a lot of military equipment charges Li-ion cells to around 4V instead of 4.2V as it results in a significantly extended life at the expense of capacity. This is true of almost all Li-ion chemistries. The only one I know of that is known to tolerate fully charged storage is LiFePO4.

author: james_s
author_rank: Super Contributor
timestamp: January 13, 2023, 06:43:36 am
content: Quote from: SiliconWizard on January 13, 2023, 02:47:02 amI bought my Lenovo X250 new in 2015. I enabled that battery preservation mode that stops charging at 80% right from the start and have only turned it off and fully charged on rare occasions. It spends most of its time plugged in and both batteries still show close to 90% of design capacity. Good quality laptops with good quality (Sony in this case) batteries can last a long time.

author: tooki
author_rank: Super Contributor
timestamp: January 13, 2023, 07:52:48 am
content: Quote from: RoGeorge on January 12, 2023, 09:19:41 pmYour mobile phone batteries are almost certainly LiPo, because it’s the technology that lends itself to the flat, rectangular battery shape, and because it weighs less.But you’re not wrong that they’re LiIon, because LiPo is a type of LiIon battery.

author: tom66
author_rank: Super Contributor
timestamp: January 13, 2023, 08:27:07 am
content: DJI drone batteries will "self-discharge" automatically after about 3-4 days in storage, to around 70% capacity. This is the battery electronics doing this, using the balance resistors on the battery pack.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 13, 2023, 10:03:54 am
content: Thank you all for clarification. Lesson learned. Maybe a little late, but we don't know what we don't know.Next question would be if anybody experimented with puncturing the skin of the battery with a small hole (without touching the internals) in order to deflate it, then covering the small hole with some adhesive tape to seal it against air.I've seen videos of people doing that (outside, toxic gases and so on), and read online about how they continue to use the batteries for years after deflating them. Others are saying aged Li-Ion batteries are a fire hazard and to never use them once they bulge, and usually the former will link to a few "classic" videos with intentionally ignited batteries.I've never seen or heard of igniting Li-Ion in the circle of known people, yet everybody I know uses phones, tablets, laptops, cameras and so on.I would like to keep using the bulged batteries for small current circuits, weather station, hallway LED lights with moving sensors, things like that where the low self discharge rate of Li-Ion will make them last much longer than the NiMH cells.Anybody tried to deflate the Li-Ion then keep using them?

author: tom66
author_rank: Super Contributor
timestamp: January 13, 2023, 10:10:28 am
content: With the cost of a new Li-Polymer battery (1000mAh is what, about 5 euros?) I would not bother. There is good chance the cell will fail and damage something worth way more than that.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 13, 2023, 11:15:41 am
content: Quote from: Infraviolet on January 12, 2023, 08:02:59 pmOnly if the cells are faulty / total crap. Normally, self discharge is nearly zero already at 50%SoC and just gets lower. Case in point, when I measured self-discharge in dozens of cells, I deliberately discharged cells to tad below 0% SoC but they did not lose any more charge during 1.5 year test period.Quote75% is not ideal. Between 30-50% could be considered ideal IMO. Although 75% is not that bad, some cell types may have increased calendar fading compared to 50%.

author: james_s
author_rank: Super Contributor
timestamp: January 13, 2023, 06:32:16 pm
content: Quote from: RoGeorge on January 13, 2023, 10:03:54 amYes people have tried this. There is not really any point, when the battery has puffed up it has been damaged, poking a hole in it certainly isn't going to improve safety. These batteries are known for catching fire if abused, do you really want to risk burning your house down?

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 13, 2023, 08:29:13 pm
content: Quote from: james_s on January 13, 2023, 06:43:36 amHaven't had that luck with Lenovo laptops myself.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 13, 2023, 08:31:10 pm
content: Quote from: james_s on January 13, 2023, 06:32:16 pmYeah, this is one of those horrible suggestions that should come with a mention in large and bold:DON'T TRY THIS AT HOME.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 14, 2023, 05:19:25 am
content: Could reuse the cell in some outdoor application where it won't be much of a big deal if it catches fire.

author: Miti
author_rank: Super Contributor
timestamp: January 14, 2023, 12:19:26 pm
content: Quote from: RoGeorge on January 13, 2023, 10:03:54 amYou don’t want to be the first one to experience this in your circle of people.Besides the toxic gases, which I understand are quite nasty, metallic lithium and oxygen don’t go well together. In a new battery there shouldn’t be any lithium in metallic form but in an old used and abused battery, you could have some deposited on the electrodes. Letting oxygen inside the pouch is not the best thing you can do. Depending on the size of the batteries that could be a problem.I have multiple RC fliers and I had puffed up batteries of various sizes over time and I never tried to puncture one intentionally, I just continued to use the least puffy for some light testing and disposed of them when they were too puffy.Edit: You may ask what’s too puffy? When the pouch is flapping in the wind when the battery is at room temperature, it is not too puffy for me. When it becomes a balloon all the time, it’s time to retire that battery.Another thing, all the RC Li chargers have a storage mode that brings the batteries to about 3.8V.

author: Miti
author_rank: Super Contributor
timestamp: January 14, 2023, 12:44:51 pm
content: Quote from: Siwastaja on January 13, 2023, 11:15:41 amI 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 14yo 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.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 14, 2023, 12:47:29 pm
content: Maybe I should just let them be without puncturing the bulged ones. The reason to deflate them is mostly to make them fit back into whatever device they use to power. DIY circuits can be made with enough space for any battery, so no need to deflate them.Another question, I've noticed these days a case where a 15+ years 1750mAh Li-Ion accumulated about 30% more charge when charged at a very slow peace, at 0.01C than when charged normally. Charging them that slow won't heat the battery, and would simplify the electronics a lot for a multi channel CC-CV charger I want to build.Would it be a bad idea to charge a Li-Ion very slow, for 3-5 days non-stop using CC-CV?

author: Miti
author_rank: Super Contributor
timestamp: January 14, 2023, 12:52:09 pm
content: Quote from: RoGeorge on January 14, 2023, 12:47:29 pmNope, 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.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 14, 2023, 02:24:27 pm
content: 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.

author: james_s
author_rank: Super Contributor
timestamp: January 14, 2023, 08:42:29 pm
content: Quote from: Miti on January 14, 2023, 12:44:51 pmThere'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.

author: Miti
author_rank: Super Contributor
timestamp: January 15, 2023, 12:16:10 am
content: Quote from: james_s on January 14, 2023, 08:42:29 pmYes, 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.

author: tom66
author_rank: Super Contributor
timestamp: January 15, 2023, 12:20:08 am
content: 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.

author: james_s
author_rank: Super Contributor
timestamp: January 15, 2023, 12:23:45 am
content: 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.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 15, 2023, 09:46:55 am
content: 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.

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2023, 09:54:51 am
content: 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 3.85-3.90VShort term storage I use 3.75V-3.80VIt 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.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2023, 10:05:23 am
content: Quote from: Psi on January 15, 2023, 09:54:51 amUsually 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 inhttps://www.eevblog.com/forum/chat/lithium-ion-battery-degeneration/msg3217888/#msg3217888)QuoteBullshit. 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 theactualfield requirements (and assuming large self-discharge is OK) are the plague of the BMS industry, though.

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2023, 10:12:39 am
content: Quote from: Siwastaja on January 15, 2023, 10:05:23 amYou 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.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2023, 10:17:47 am
content: 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, Ihadto repair it properly the next day anyway.

author: magic
author_rank: Super Contributor
timestamp: January 15, 2023, 12:03:01 pm
content: 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.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2023, 01:08:31 pm
content: Quote from: magic on January 15, 2023, 12:03:01 pmAnything 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.

author: BravoV
author_rank: Super Contributor
timestamp: January 15, 2023, 01:18:07 pm
content: 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=1h7m5sEven though its a 1 hour 14 mins video length, recommending to watch this Prof. Jeff Dahn video from the beginning, its very informative, imo.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2023, 01:24:53 pm
content: Quote from: BravoV on January 15, 2023, 01:18:07 pmAs 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/#msg3217888I 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.

author: tom66
author_rank: Super Contributor
timestamp: January 15, 2023, 01:27:04 pm
content: 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.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2023, 01:29:20 pm
content: Quote from: tom66 on January 15, 2023, 01:27:04 pmAccording 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.

author: BravoV
author_rank: Super Contributor
timestamp: January 15, 2023, 01:49:10 pm
content: Quote from: Siwastaja on January 15, 2023, 01:24:53 pmAccording to an "anonymous" source in some public forum, compared to Prof. Dahn, yeah, right.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2023, 02:40:36 pm
content: Quote from: BravoV on January 15, 2023, 01:49:10 pmRead and try tounderstandwhatis said, instead ofwhois 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.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 15, 2023, 02:50:44 pm
content: Quote from: magic on January 15, 2023, 12:03:01 pmThat's what I come with, because I have plenty of DZ4V3 (NOS), and power LEDs with radiator (from bad light bulbs):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).

author: james_s
author_rank: Super Contributor
timestamp: January 15, 2023, 07:16:07 pm
content: Quote from: RoGeorge on January 15, 2023, 09:46:55 amThey 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.

author: thm_w
author_rank: Super Contributor
timestamp: January 16, 2023, 11:38:10 pm
content: Quote from: james_s on January 15, 2023, 07:16:07 pmA 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.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 17, 2023, 11:38:38 am
content: 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.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 17, 2023, 11:58:48 am
content: 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

author: MadScientist
author_rank: Frequent Contributor
timestamp: January 17, 2023, 05:38:37 pm
content: 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 pointLong term storage is best at 60-70 % SOC but really fine upto 80% SOC avoid very low Soc for storage or below 40% SOCIn essence short high current charge ( relatively high ) is best once the correct safety regime and a proper stop charge point is set

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 17, 2023, 08:37:26 pm
content: Quote from: MadScientist on January 17, 2023, 05:38:37 pmIn my experience mentioned earlier, a combination of a 0.1C charge current and automatically recharging the battery, keeping it at 100% most of the time, was a sure recipe for dangerous bulging and killing the batteries.Thus, any UPS system based on Li-ion batteries should definitely be designed appropriately, and there's little surprise lead-acid batteries are still popular in UPSs.

author: thm_w
author_rank: Super Contributor
timestamp: January 17, 2023, 11:05:57 pm
content: Quote from: MadScientist on January 17, 2023, 05:38:37 pmCitation? What I'm reading shows the opposite.And any any sort of cycle life studies all get better as charge rate decreases, down to 0.2C or 0.1C, is about the lowest. I don't see any studies lower than that."Temperature rise due to reaction and joule heating accelerates the SEI layer growth and causes more capacity loss"https://iopscience.iop.org/article/10.1149/06127.0043ecstThis might be relevant to what you are talking about though: "The kinetically limited expressions from equations 2 and 3 are qualitatively similar, with both showing much greater SEI growth during the later stages of charging, especially the CV portion of charging. "https://iopscience.iop.org/article/10.1149/2.1161412jes

author: MadScientist
author_rank: Frequent Contributor
timestamp: January 17, 2023, 11:11:05 pm
content: The studies are there if you Google them. Trickle charging has never been recommended for li ie very low fractions of CLi performs best if the charge cycle is as short as practical consistent with safety and battery max specs

author: tom66
author_rank: Super Contributor
timestamp: January 17, 2023, 11:19:10 pm
content: 0.1-0.2C charging rate would be about normal for an EV battery (~60kWh pack, 7kW AC charger), yet the data shows that rapid charging (while the effect is not hugely significant) is definitely more damaging to the cells than slow charging. So I'm not sure I accept the SEI layer buildup stuff.

author: thm_w
author_rank: Super Contributor
timestamp: January 17, 2023, 11:36:49 pm
content: Quote from: MadScientist on January 17, 2023, 11:11:05 pmrightttt so its on me to find the proof of your claim, which contests with existing studies.Lower charge rates results in longer cycle life, down to 0.2C or lower.https://www.researchgate.net/figure/Capacity-development-vs-equivalent-full-cycles-depending-on-the-charging-rate-of_fig4_286242928https://www.sciencedirect.com/science/article/abs/pii/S0378775318310462https://pubs.rsc.org/en/content/articlelanding/2018/ra/c8ra04074e(LiFePO4)https://www.osti.gov/servlets/purl/1397110(some C/10 cycle tests)

author: JDubU
author_rank: Frequent Contributor
timestamp: January 18, 2023, 12:34:36 am
content: RoGeorge:Do not puncture a lithium ion battery pouch under any circumstances!!!The liquid electrolyte is a lithium fluoride compound that will convert to hydrofluoric acid in the presence of moisture. Hydrofluoric acid is a very dangerous contact poison.It also stops being a battery if any moisture is present in the electrolyte.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 18, 2023, 09:50:56 am
content: Thanks for the warning. Did that outdoors. Poked a pinhole in the swollen layer only, let the gasses inside escape and squeeze/flatten the battery case, then covered the pinhole with self adhesive Scotch-like tape. The pressure inside was bigger, so I hope not much air entered the battery. Also it's winter here, so even if some air entered the battery, humidity was low.I knew abut nasty HF and avoid inhaling, thought it smelled sweet for a short moment. The sweet smell reminded a little about vintage electronics and tube radios, that smell very close to the sweet smell of very old paper books with yellowish pages. Not the same smell, but close.The battery is a small 300mAh Li-Ion that was so bulged (about 3-4 times its nominal thickness) that I had to remove it from a TEAC mp3 player years ago. It sat bulged like that and unused on a shelf for about 10 years. Charged discharged it before and after deflating. Still working, just that it lost about 1/3 of its capacity over the years. For now I don't plan to reuse that battery.As for the other Li-Ion batteries leftovers from mobile phones, if I will ever reuse them, will let them bulged as they are. No need to deflate since the DIY enclosures can be made big enough.

author: tooki
author_rank: Super Contributor
timestamp: January 18, 2023, 07:05:39 pm
content: Quote from: RoGeorge on January 18, 2023, 09:50:56 amAre you insane?!?A swollen lipo pouch belongs in exactly one place: the recycling bin. Continuing to use it is asking for trouble.And when I say trouble, here’s some context: every Apple Store has a battery fire box and basic firefighting equipment in their repair room — and this despite the fact that if a device comes in with a swollen battery, they won’ttouchthe battery in-store, and instead replace the device and then refurbish the swollen device in a repair depot. (Battery swaps are done in-store if the battery isn’t swollen.)

author: Siwastaja
author_rank: Super Contributor
timestamp: January 18, 2023, 08:18:11 pm
content: Quote from: tom66 on January 17, 2023, 11:19:10 pmOr even just 2-2.5kW, so 0.05C is perfectly normal.Never heard about the low current SEI thing, either. Have read quite a few papers.

author: james_s
author_rank: Super Contributor
timestamp: January 18, 2023, 09:02:23 pm
content: Quote from: SiliconWizard on January 17, 2023, 08:37:26 pmRegular Li-ion is a poor choice for UPS duty. LiFePO4 is a much better choice, they are way more robust and tolerate fully charged storage well. They're a lot harder to make catch fire too.The energy density is lower which limits their use in portable electronics and flying toys but they do get used in power tools.

author: Bud
author_rank: Super Contributor
timestamp: January 18, 2023, 09:09:25 pm
content: Quote from: tooki on January 18, 2023, 07:05:39 pmThat is just "think of the children" mentality.

author: james_s
author_rank: Super Contributor
timestamp: January 18, 2023, 09:14:44 pm
content: Quote from: Bud on January 18, 2023, 09:09:25 pmIt is a bit silly. Just drain the battery, a battery in a low state of charge, whether swollen or not is pretty inert.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 18, 2023, 09:17:00 pm
content: Quote from: tooki on January 18, 2023, 07:05:39 pmHe got warned enough, I think. Now he mentioned a pretty low-capacity battery, so the risk was minimal in terms of fire. The nasty chemicals, OTOH, is something else.Quote from: tooki on January 18, 2023, 07:05:39 pmYes, but not in the general trash bin, please. This is dangerous and illegal in most places. Dispose of it in appropriate bins.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 18, 2023, 09:19:20 pm
content: Quote from: james_s on January 18, 2023, 09:02:23 pmDefinitely. I would never use Li-ion for back-up power purposes, even for relatively low capacities, after this unfortunate design.But we can still see back-up systems with Li-ion batteries, and see people asking about that on forums on a regular basis, so I think it's worth talking about it.And LiFePO4 is much, much better indeed. That's what I would recommend as well.

author: james_s
author_rank: Super Contributor
timestamp: January 18, 2023, 09:22:23 pm
content: Quote from: SiliconWizard on January 18, 2023, 09:17:00 pmIt's always been accepted practice in the USA to discharge pouch cells and throw them in the regular trash, I'm not aware of any regulations against doing that.Those little ones that are under about 500mAh are pretty safe. I have burned up a worn out one on purpose before to see what would happen. It wasn't very exciting, it just puffed way up, melted a hole and then there was a flame much like from a candle that came out for a few seconds and then it sat there smoking.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 18, 2023, 09:28:23 pm
content: How did you ignite it?

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 18, 2023, 09:35:38 pm
content: Quote from: james_s on January 18, 2023, 09:22:23 pmCertainly not in the EU, at least! There is always this crossed waste bin symbol to make it clear.https://www.compliancegate.com/lithium-battery-safety-standards-european-union/

author: james_s
author_rank: Super Contributor
timestamp: January 18, 2023, 10:37:01 pm
content: Quote from: RoGeorge on January 18, 2023, 09:28:23 pmConnected to a bench PSU and overcharge it, they self ignite.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 19, 2023, 12:26:36 am
content: What current voltage did it caught fire?Was that with or without the small Battery Management System PCB on top of the battery?The mobile phone cells always come with a small BMS inside. I know for sure the BMS will disconnect the battery at lower than 2.8V (it happened with a few batteries while I was discharging them to measure their capacity).The internal BMS is also supposed to disconnect the cell at more than 4.3V charging, or at a short circuit (high current, don't know which I value). So far never tested the overvoltage and the overcurrent limits.

author: amyk
author_rank: Super Contributor
timestamp: January 19, 2023, 01:52:56 am
content: Quote from: JDubU on January 18, 2023, 12:34:36 amYou'll get HF if the battery burns (due to fluoropolymers being used in the separator), but the electrolyte itself is relatively tame.

author: james_s
author_rank: Super Contributor
timestamp: January 19, 2023, 02:04:53 am
content: Quote from: RoGeorge on January 19, 2023, 12:26:36 amI don't recall the voltage, it was a few years ago and there was obviously some drop over the wires anyway. It was a model aircraft battery without any BMS, I've heard other cases of them catching fire around 5-6V. There have been quite a few fires, mostly from people setting up their chargers incorrectly, some of the older chargers didn't monitor the balance leads. Multiple guys on the RC forum lost their houses, several others had workshops and cars burn down.

author: JDubU
author_rank: Frequent Contributor
timestamp: January 19, 2023, 06:53:50 am
content: Quote from: amyk on January 19, 2023, 01:52:56 amTake a look at this:https://www.nature.com/articles/s41598-017-09784-z

author: tooki
author_rank: Super Contributor
timestamp: January 19, 2023, 07:42:00 am
content: Quote from: Bud on January 18, 2023, 09:09:25 pmNo, it’s simple risk mitigation (which insurance companies likely insist on) and time management. It’s not worth the time of store employees to figure out if a battery is discharged enough to be worked on safely. (A battery replacement is a 15 minute schedule slot.) Just send the customer home happy, quickly, and let the repair depot deal with it later.The point is, batteries in that state are certainly not safe enough to beput back into service!!Quote from: SiliconWizard on January 18, 2023, 09:17:00 pmYep, which is why I said recycling, not trash. (I assume enough intelligence on the part of our readers to understand that this means thecorrectbin for the item being disposed of. …ok, fair enough, given that this dude wants to reuse it, it probablydoesneed to be stated explicitly!) Put used batteries into the battery recycling bin.

author: magic
author_rank: Super Contributor
timestamp: January 19, 2023, 09:19:32 am
content: Quote from: tooki on January 19, 2023, 07:42:00 amThey certainly don'tlookgood, and I imagine that alone would be an overriding concern at Fruit Inc™This whole thread rises more questions than it answers. Maybe some experimentation would be in order.Are discharged batteries really inert and inflammable? What if you outright put one in fire?Is there enough HF in a swollen battery to actually poison yourself?How many normal charge cycles before a swollen battery catches on fire? Does it ever?BTW, I have seen a swollen battery which apparently had been in use for a while, without the owner noticing.The owner only complained about capacity not being what it used to be.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 19, 2023, 09:37:03 am
content: Quote from: tooki on January 19, 2023, 07:42:00 amWould you kindly fuck off?Hold your innuendos for yourself.Here's a basket for your advice:You are on my ignored users list.

author: magic
author_rank: Super Contributor
timestamp: January 19, 2023, 09:46:35 am
content: To be fair, I always thought that continuing to use already failing Li-ion batteries is a bit nuts, but I'm curious how nuts it is exactly because there doesn't seem to be much reliable information on thatAs for the rest, it's just your typical American leftoid behavior. Hiding posts of such users would deprive me of some entertainment.

author: tom66
author_rank: Super Contributor
timestamp: January 19, 2023, 10:37:16 am
content: How did Li-Po cells turn into politics?Before a Li-Po cell fails explosively (e.g. due to overcharge) it tends to bulge up in much the same manner. I would not be surprised to see these batteries burst and burn, but maybe it turns out that the slower version of this process results in a bad cell, butnotan exploding cell. I'd still argue it's way more of a hazard than a normal cell, and I can't blame a repair shop for not wanting to be involved.

author: tooki
author_rank: Super Contributor
timestamp: January 19, 2023, 09:29:39 pm
content: Quote from: RoGeorge on January 19, 2023, 09:37:03 amIf it looks like a duck and quacks like a duck…Quote from: RoGeorge on January 19, 2023, 09:37:03 am::tiny violins:: 🎻 🎻 🎻

author: tooki
author_rank: Super Contributor
timestamp: January 19, 2023, 09:30:48 pm
content: Quote from: tom66 on January 19, 2023, 10:37:16 amWell, in reality, it didn’t, other than one cryptic, nonsensical remark by magic.

author: james_s
author_rank: Super Contributor
timestamp: January 19, 2023, 11:44:01 pm
content: Quote from: tom66 on January 19, 2023, 10:37:16 amOvercharged cells will puff up before they burn, but it's also common for cells to puff up due to normal wear and degradation. Lots of guys keep flying slightly puffed cells, haven't seen one burn up yet, so it's not necessarily dangerous, but a puffed cell is definitely not going to perform like new either. If it is severely puffed I would discharge and dispose of it.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 20, 2023, 08:10:45 am
content: Slight puffing seems to happen to almost any old cell. The difficulty is defining what is too much and how dangerous it is. I have never seen good data about this, it's all hand-waving, even among experts.With hard-cased cells like 18650, you just can't see the internal pressure rise equivalent to this "slight puffing". When the pressure rises too much, the safety went (CID) disconnects the internal cell from the terminals, so the choice is made for you and the level of "puffing" hidden.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 20, 2023, 09:00:57 pm
content: Quote from: Siwastaja on January 20, 2023, 08:10:45 amYep and yep.All in all, when we finally switch to a different battery technology on a large scale, I won't miss Li-ion. One bit.

author: james_s
author_rank: Super Contributor
timestamp: January 20, 2023, 09:10:25 pm
content: I'm not too confident that we will switch to a different battery tech. I recall reading that the properties of lithium are about as ideal as we're going to get as far as energy density, there is nowhere else to go up the periodic table, lithium is already the lightest metal. I'm sure batteries will continue to improve and we will probably see other types with other advantages but in terms of raw energy density I'm skeptical.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 21, 2023, 08:26:13 am
content: Quote from: SiliconWizard on January 20, 2023, 09:00:57 pmYeah, but to be fair, having seen the transition from lead acid, NiCd and NiMH to li-ion, I won't miss any of them. One bit.

author: IanB
author_rank: Super Contributor
timestamp: January 21, 2023, 08:55:23 am
content: Quote from: Siwastaja on January 21, 2023, 08:26:13 amThe major problem I have with Li-ion is the way the batteries tend to be embedded within the device and charged in place, rather than being removable. This is why I still very much like devices that take AA or AAA cells, since when the batteries are low I can simply swap them for fresh ones and put the depleted ones on charge. With lithium batteries, when the battery is low I have to plug the device into a charger and wait an hour or more for it to recharge. And when the battery wears out the whole device is often thrown away.I understand that some very small devices take advantage of the embedded battery for the form factor, but I still find the overall trend to be a loss of convenience.

author: MadScientist
author_rank: Frequent Contributor
timestamp: January 21, 2023, 09:14:03 am
content: Quote from: SiliconWizard on January 20, 2023, 09:00:57 pmLiTO is probably the safest li tech it doesn’t even need a BMS.BUT after that we’re a long way from alternatives and any high capacity energy store has risks.