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Are over-discharged lithium cells safe? (And how to test for damage.)
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- Опубликовано: 20 июл 2017
- This is one of the best Poundland purchases I've made in a while, purely because of the Google trek for knowledge that it sent me on. Most of Poundland's power banks in this style come completely discharged due to the higher than usual quiescent current of the circuitry. I wanted to know if that was a serious issue or not.
Here's the best documented test I found.
www.nature.com...
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
www.bigclive.co...
I know this is an old video, but I recently had success reviving a Milwaukee drill battery. The charger wouldn’t even think about charging it because the cells were discharged well below the threshold. It sat that way for months. Just for science I hooked it up to my bench PSU and set it to the packs voltage and 3A. I sat and watched it go up and kept putting it back onto the charger until it would charge. I ran it through a couple charge/discharge cycles and it has been holding a full charge for 2 months. I was pretty surprised, and saved a $100 battery. Great video!
Did the same with a Ryobi 18v battery. Since it was still within their warranty period, they sent me a new one and told me to recycle the "defective" one. Essentially gained a free battery.
I have read an article about modern laptop batteries where they are sometimes designed to fail permanently. The circuit board has trippable switches to disable the battery entirely or specific cells that are bad. If you try to replace the cell the battery still won't work due to the circuitboard trip switch which is permanently tripped. (Not sure of the correct term for this)
There are sometimes chances to replace a cell , but you have to do some hackery like keeping the old dead cell connected while adding on the new cell, or equalizing the voltage of the old cells and new one, else some imbalance trips the battery circuitry and the battery will be permanently disabled. (Even though you have now fixed the battery, the circuitboard won't allow its use or charging)
I'm not sure if your tool batteries are designed the same way though
Update: 2 years on and the battery I jumped is still working!!!
One of the most useful RUclipss I have watched. So enlightening to have this when there is so much ridiculous commentary on lithium batteries. The simple measurement of the holding voltage to test cell status is a godsend for making sense of these amazing batteries. Also getting an intelligent charger for £1 plus a battery & box is an extraordinary bargain. Thank you!
The world is full of idiots who can't understand any semblance of risk except for the sensationalist kind. Even taking the Note 7 in isolation the battery failures were at most a few dozens out of ~10 million broken-by-design handsets, but no, my life is more valuable for crossing the road blindly while texting.
I've been using lipos for 10 years - RC models, electronics, etc. That's the first understandable, proper scientific explanation I've heard. thanks Clive.
Hello Clive,
I would be cautious about recovering cells from below ~1V. I once left a 20Ah Li-ion (NMC) pouch cell plugged in to the load bank on the bench, forgetting the load bank would continue to discharge the cell when off. Monday morning, my boss showed me how the cell had gone from being firm to really floppy, indicating loss of structure. We disposed of the cell. This loss of structure obviously won't be visible with an 18650 cell due to the metal can. Would be interesting to repeat this test on your "9V" lithium-ion battery's pouch cells.
I was once told by a Li-ion chemistry expert that discharging a Li-Ion below 1V would completely de-lithiate the cathode, and collapse a lot of the structure, resulting in capacity loss. If charging too rapidly after that, lithium dendrites could form, triggering a micro-short circuit (which may/may not burn off). For this reason, (and also thermal dissipation as you pointed out) charger circuits usually do a 1/10th of normal charge current until the cell is closer to 3V, then they charge at full current. I have however seen some chinese designs that merely use a diode+resistor from a USB connector direct into the cell, and rely on the cell's protection circuit to cut off the charging when full. Pretty sure if it wasn't legally required to fit a protection circuit, they would omit that as well.
I've also seen power banks that fail if they aren't charged regularly, the power bank circuitry self-discharge takes the cell fully flat after many months. After that, they often have poor capacity and don't keep charge.
So, my conclusion is, over-discharged cells should be viewed with suspicion, and not fitted into a serious product. If you have to use them, charge slow, and never leave unattended. I have seen cells that just sat at around 2.4 to 3V and took ~1C charge and just got hot - eventually, in a confined space, if they get to runaway temperature you could have a fire(work). For this reason a lot of chargers have a timer limiting max charge time.
At a previous job, we would screen every new battery's voltage when it arrived - after 6 weeks in a shipping container en route to us, if it had discharged itself,the voltage would be low, and we would reject those cells below ~3V. So i can confirm your method of screening for faulty cells with self-discharge does work, and has worked for me for 100s of thousands of batteries screened.
I have a power tool battery I did this to and it is still working 2 years later....
@@optimizelogicrepair2784 I recently did some tests with Lithium-Iron Phosphate cells, and was able to take them down to 0V for an hour or two and then use the charger's recovery feature to slow charge them out of the dangerously low voltage zone. After that, they came back and worked fine, with barely any loss of capacity. But I wouldn't do this with other Lithium-ion chemistries, I've seen too many that swelled up or didn't recover properly.
Science should have a proper word for "disrupts the chemicals a wee bit".
How about "footers it"
mikeseloquencestuff.
oh, hi mike!
Trembling, perhaps.
It's SHITENED!
Cow-mined, wormwelled...?
Really interesting summary thanks Clive. I'm currently processing 18650s from laptop batteries and many are coming out at less than a volt. I give them a slow charge at about 50-100ma for a while until they reach 3v and then crank up the current in stages. They all seem to charge fine after this point. The plan is they will all then sit in a box for a month and I'll check the voltage after that and make decisions on which to keep and which to recycle.
Adam Welch I tend to find the best batteries come from packs where one of the three sets is dead. So my voltages are 4.1, 4.1, 0.7
Samuel Seidel You can see why. When one fails prematurely the others should have a good life left in them. All mine seem to have been left for a while self discharging or the BMS has completely failed meaning they've all gone very low. Hopefully there is life in them yet.
Hi Adam, just wondering what are you using to charge these at this voltage?.
I just tore abpart the battery pack from an ancient Windows 95 era tablet, two of the cells were dead, the rest had around 2.5 volts or better, even after laying in my back room for years. I put them on a charger and charged them up to a full charge, they are holding just fine. Funny looking little thin square cells that were packed in single rows of four each for a total of only 8 of that six of them are working fine, I plan on using them in projects that are in need of rechargable batteries. I build mostly ghost detector type toys for my niece who thinks she is a psychic or some damn thing and goes on those stupid ghost hunts all over the tri-state area. They cost so little to build and maker her so happy that it's must makes the building fun.
The Littokala 500 is a great charger, it charges at 300, 500, 700, and 1000mah and also tests capacity they are great for recycling laptop cells.
Years ago, I had an old DELL PDA that was actually my favorite toy for a few years because you could flash other oS's on it. The major problem with them was that they ate the power from the battery pack and killed the cells with great regularity. About two weeks ago, I found one of the old cells that I had written DEAD on it in red sharpie. I tried my VOM on it, and nothing, so I had just saw a comment on some page that if you shorted those cells across another good cell for a few seconds, it could revive it. I gave it a try, and the blasted little cell came to life! I soldered some wires on her and was using it to power a small ESP8266 01 with a tem/humidity shield on it. It powered the little guy for about a week straight, then went dead. Now she is plumb dead, I tried shorting her again across a good cell and put my charger on it, but nothing. Well it was fun while it lasted.
"massive heat incident" is a great band name.
sounds more like me on the toilet.
tohopes right now yes because hate a bowl of cereal for lunch about 9 hours ago. luckily it takes a decent amount if time for this to happen and it's not normally within a couple of hours. this gives me some time from ingestion of dairy till I'm blasting the rocket launching pad with a unholy hell spew of yuckyness. May be tmi
massive heat incident fire....gotta add "fire" to the end of it...
Karl Kornel -likes comment-
No it isn't
+ tek413 I know your problem.
I have to hold myself down to the toilet seat really hard so i would not levitate around while shitting my bath...
I've found one of the best ways to test for damage to lithium cells is by letting them sit a good 20 minutes in a campfire. If they pop or explode rather than emitting angry, squealing jets of bright flame, they were probably ok.
If destructive test is "one of the best ways" I think we need further research in that matter :D
Don't try this at home kids! The camp fire will damage the floor coverings. Use Mummy's microwave instead!
Sounds quite like my fuse tester, if the lamp flashes, the fuse was good.
Sounds like the way they tested if you were a witch.
*Destructive Testing,* yes!
About 8 years ago, I purchased north of 50 Compaq laptop battery packs. Brand new with a date code 1995. The cells read about 0.1 - 0.5v . I charge them at 2.8v 10ma (takes about 10min. to reach 2.8ish v) them finished the charge at 4.21v 500ma. A&TB Cells rated (1c) 1500mah. Most tested between 1350-1550mah. I just finished breaking up my last 10 packs and now 27 years old they tested fine. I've made many projects over the last years and they work fine.Nice for 5w 18650 flashlights.
*"Bring* *the* *reactor* *power* *down* *to* *250* *megawatts,* *then* *we* *can* *start* *the* *test"*
Sir, the guidebook says that we should start the test at 700-800 Megawatts...
Lutz Peyton You idiot you stalled it! Restart it! Sir we shouldnt ...xenon poisoning. Never mind...take all the control rods out to start it again...
Sir, the control rod caps are shifting! These things are like 500 pounds!
The rest,as they say, is history!
@@linkrobinett1832 He's delusional. Get him out of here.
Great stuff as always. Kinda been wondering why single cell schemes, other than the note thing, have been largely quiet when it comes to events
One thing I have noticed through disassembling a number of these packs is a rare few have sprung terminals and not solder tags. Which is great for using it as a cell charger
Eminently educational video, Clive!
This makes things so much clearer for me. I've never used Lithium ion cells in any project, but I have a few salvaged 18650's just waiting to become useful again. Finally I know what I need to do to check if they're of any use and how to recover them.
Thank you! Now I'm off to peruse the article.
The problem with the Internet is that there are far more "experts" than there are people who really know what they are talking about. I used to experience a similar situation in science education. Lots of people would say that "such and such an experiment is banned", they very rarely were. I actually worked on the safety committee of the largest education authority in the UK, and was forever having to debunk urban myths.
Discharging it close to 0V causes a high self discharge, but it seems to disappear after about 5 cycles.
yes i see your video about it it is awesome you and clive give me aloot of information about these
I like this channel a lot, but this is an exceptional useful video, thanks Clive for taking the time to research this and share it, two thumbs up.
The story I always heard about low state-of-charge li-ions is pretty much what you said at 10:00. Not that they're incredibly dangerous or anything, but just that they have to be charged super slowly until they get to a more normal range to avoid trouble. And that sometimes you get screwed by a protection circuit because it will do a hard cutoff when it gets undervolted enough, which prevents you from ever charging the thing up again.
Makes perfect sense Clive, I wonder how many 18650's have been dumped simply because their open circuit voltage was considered 'too low'.
On different types of batteries I've had successes by aggressively overcharging them for a short time to burn clear any slight internal shorts.
Though 'The internet' won't believe me because, reasons.
More or less, just keep an eye on temperature and don't let the current go silly high,
i've used high current pulses to attempt to recover nicads and nimh, very hit and miss and all cells i've done it to that seemed to recover failed again and in some cases leaked after a while.....although quite a long while !
It's worth a go isn't it?.
I use a somewhat beefy 10-30W 12V center tapped wall adaptor in reverse wired as a Joule Theif using the center tap. Power for that comes from a regular smps wall wort. You take the output that's normally the mains side, and feed it into the cells through a diode. 25-50mA or so is the output, peak to peak 175V, and most of the current is delivered under 100V (30-70-ish). Also works great to desulphate Lead Acid batteries. PS: Don't touch the output.
I recovered a lipo pack that had been discharged to about 1.5V/cell, and it worked perfectly for about two weeks, no noticeable self-discharge and normal capacity. After those two weeks, however, I noticed that the pack had puffed considerably. It still worked, but other packs of similar age that hadn't been deep-discharged did not puff.
Yeah the Samsung Note 7 was a mechanical failure, not a chemical one.
It's nice to know that what I was taught in Uni is actually the same as what really happens when overdischarging. Except the bit with recovery from REVERSE charging being so likely. funny.^^
I think its the same phenomenom when he said that cell that are fully discharge (near 0V), he cherge them and they wherent d
Surprisingly this video remains highly underrated.
Very educational as always! I've only recently got myself one of these to play with around a week ago - I shall monitor the cell voltage over a few days to see if it's bad or not. Thanks Clive!
The only issue with heavily discharged cells I've found is my favorite charger refuses to accept them as anything other than 1.2V cells, and my hobby charger flat out says no and angrily beeps at me.
Normally, a quick zap on the bench supply limited to say 100ma, perks them right back up.
I have never had a cell do anything... funny, afterwards. Only a bit of lost capacity.
It's worth noting that you can do this to other rechargeable chemistries too.
Once or twice a cell wouldn't take a charge, and I've just straight up told my bench supply to blast the cell for one or two seconds with thirty volts at five amps, in the hope of just burning through any internal shorts. I've brought several cells back to life this way, and have yet to have one be problematic afterwards. Usually quarantine them for a day or two in a steel box after, but no problems.
Thanks Clive, I needed 4 cells for a project but didn't want to spend too much on them. Bought 4 of these packs, all of them were down to around 1V after watching this VERY informative vid (pity about the audio but you can't have everything!) I "Jumped" them from a good cell while using their own charge circuits and all is fine with them, charged nicely and no discharge when left standing (after disconnecting from their circuits)! Will send a thank you donation when I get paid this week.
Well, that was a very informative Big Clive video right there. Cheers mate.
I have recovered a lot high current LiPo cells (those for RC planes or quadcopters) that were sub 1v. Some of them have swollen but they take the charge and hold it normally. The ones in worst shape (twice the thickness from swelling) grew some internal resistance but they were still fine for 2 A loads, instead of the rated 40 A.
In the RC hobby, most of the guys throw away packs at the slightest sign of gassing. That's surely a waste.
Giovanni Carlo Iglina What would you do if you need 40A but the pack can't handle it any more?
noXi Buy a new pack
One or two Modellers have had fires one in our club kitchen fire, most packs like this end up with high internal resistance which are no good for model helicopter which have a high current demand. From full capacity to 20% in 4 minutes or less.
Myself I would also get rid of swollen LiPo packs as it's a sign that something went/is wrong with it. They are not really worth taking risks with as they can burst into flames without warning.
For my and 2 my friend experience they are as stable as the others. The only pack that went on flame for the 3 of us was a new pack with 2-3 cycles and perfectly flat. It was standing there on a table and went thermonuclear by themselve. Just my experience. Yes they grew a high internal resistance, but are perfectly fine for FPV video receivers or monitors/goggles.
Thanks for this video! Not only did I learn a lot about lithium batteries, I also didn't know about the resistive regulation in the power bank charging controllers. So it's not the cell that heats up … hopefully.
Good video and interesting paper. I've been getting these units from Poundland for a while as the cells are quite good. I take the cells out and charge them at
The problem with overdischarged and generally maltreated cells is you just dont know how their chemistry is going and if it has weak points (like SEI disintegration, growing dendrites can be lithium or copper! and so on). I have harvested many used cells from laptop batteries and ebikes and most of the overdischarged cells come to (some) life again when you laod them with low current with a normal bench power supply. My general experience is that cells which have been sitting at 0 volts for quite a time are bad, they may charge but they have very high self discharge rate. Some even get quite hot when charging - meaning they have (small) internal shorts from dendrites. These dentrite can occur in 2 ways: from overcharging, overcurrent and aging they grow lithium dendrites. Copper dentrites typically occur when they are overdischarged - the deeper the more. SOC -12% is a barrier where they definetly will build up and become stronger - giving high risk for a severe short! But they also can occur at below 0% SOC and any undervoltage lower than 2.5 V. Generally i would say cells over 1.5V maybe still be reasonably safe to use - but never unattended! Cells below that are more and more unsafe - although probability that something goes terribly wrong will be still low - but who wants to take the risk??
I tend to decide on the self-discharge rate: i let the cells sit for 3 days after charging (to around 4V) measure the voltage first time, then measure again 1 week later: if it has lost more than 10...20 mV its a bad cell. (This is not a fixed value - you can adjust it to your fellings/needs - but i would say more than that is too high). A new and good cell typically wont loose even 1 mV in a week. The best cells i have loose just a few (1-5) mV per year! Keep in mind: the higher the initial voltage the bigger the loss (esp. the first days). To be compareable you should charge them all to 50% SOC and start the measurement from that point.
Here is a lot of scientific input if you are interested:
A Critical Review of Thermal Issues in Lithium-Ion Batteries:
jes.ecsdl.org/content/158/3/R1.full
scientific research (article from above)
www.nature.com/articles/srep30248
overdischarge:
www.sciencedirect.com/science/article/abs/pii/S0378775306004277?via%3Dihub (excerpt)
Internal short circuit detection algorithm and procedures:
www.sciencedirect.com/science/article/pii/S0306261915012465?via%3Dihub (excerpt)
A General Discussion of Li Ion Battery Safety:
www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=15&cad=rja&uact=8&ved=2ahUKEwjaxvLKgN3kAhXGIVAKHXMnBZU4ChAWMAR6BAgFEAI&url=https%3A%2F%2Fwww.electrochem.org%2Fdl%2Finterface%2Fsum%2Fsum12%2Fsum12_p037_044.pdf&usg=AOvVaw137EADCJakEAZGTzV4amGl
Thermal Stability Studies of Li‐Ion Cells and Components:
www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&cad=rja&uact=8&ved=2ahUKEwjaxvLKgN3kAhXGIVAKHXMnBZU4ChAWMAB6BAgBEAE&url=http%3A%2F%2Fjes.ecsdl.org%2Fcontent%2F146%2F9%2F3224.abstract&usg=AOvVaw1gSKvVn2iMGeQxhO2PR3wZ
"Nobody is asking for a thinner phone, but they are asking for more battery capacity"
"Nonsense, let's make the phone comically thin and the battery explode"
Watching this channel, I oscillate rapidly between thinking that a power bank would be a really useful thing to get and thinking that having one would set my satchel and laptop on fire without warning.
This phenomenon often occurs even in today's Ni-MH modern cells- I am writing this based on my experiences and observation . Especially in cheap enviroments like popular 1xAA or 1xAAA solar lights. When the boost converter draws every Wh from battery and it provides to completely discharge and in the worst case even with swapped polarity phenomenon. It's really interesting because it is kinda "silent knowledge", could you @bigclivedotcom ever make a material about it?
P.s Very intriguing material, thumb up, keep it up and best wishes!
Clive, Very informative video. After viewing, I had an old (10 years old more or less) Dell Inspiron e1705 battery (6 18650 lithium ion cells) which I carefully disassembled. I then checked the charge on them. Of course all were well discharged. One in particular was at .074 volts. So I trimmed the extra off the tabs and put it in a Dorcy rechargeable flashlight which also functions as a battery pack and let it charge. BTW the flashlights case is very thick cnc'd Aluminum (so I was not too worried about it overheating). I did keep a close eye on it however. The battery charged and indicated a completed charge on the flashlight's charge led. I then tested the voltage and it was around 4.2 volts. I have been using it in the flashlight for about two weeks now (normal usage) and as of this moment 12 noon California time on July 20th 2022. the charge is at 3.562 volts. The flashlight has battery monitoring circuitry, so I will see how long it is from now until it indicates the need for a recharge. At that point I will check what the voltage is. I am expecting it to be about the discharge cutoff voltage you mention in this video. If so I will charge it up again and see what voltage I get. And before a bunch of you start saying how dangerous this can be, I will only be using the batteries in this particular flashlight (it is kept on my desk in plain sight at all times). Thanks for this video Clive it will allow me to put some batteries back in use that otherwise would have gone straight to recycling.
I turned off my adblocker JUST for your channel because I love you so much 😩😩
I had a cell that had battery protection, it hadn't been used for a long time, it would not take a charge, it was at about 1v, i guessed that the protection circuit was stopping it from charging (for safety), so i started with a 1k resistor on 5v direct to the cell, and monitored the voltage, it crept up slowly, so i used a 500 ohm, it was going up in voltage a bit quicker, but under control, eventually it got to around 3.5 and was able to complete the charge via the normal circuit, that cell is still fine several months later.
The way battery protection works is that it turns off the discharge but still enables charging. Most phone PMICs don't attempt to charge when they don't see a battery voltage at all, but Tp4056 and many power bank circuits usually will trickle charge it, see if it recovers, and then charge it normally. Always a good idea to keep something like that around.
Siana Gearz, that's the way they are supposed to work. However as the FET's are enhancement mode it simply will not charge if the battery is too low as you wont reach gate threshold if it's a crap circuit.
Gordon, why? You're basically charging through the reverse body diode initially, you don't even need the gate. Plus when the charger is in initial recovery trickle charge mode, it limits current, not voltage. Given that initially no current flows (your condition: battery is not charging), there will be plenty of voltage.
The cell i had came from a piece of equipment , i doubt the protection circuit was cheap, i think it was done on purpose so you didn't charge a dead cell in the conventionaal way.
Your second assumption (which should be correct) is that the FET is either directly or indirectly fed from the voltage on the output of the circuit. Sometimes it is only powered from the battery. Hence my "crap circuit" comment because even though it should be as you say in a well designed circuit, some of the circuits seem to have been designed by a deranged sloth. As for the body diode, again you should be correct but even some of the silicon is badly designed so effectively you get a zenner in reverse series with the body diode (and this in turn introduces even more parasitic components) which buggers up all sorts of parameters. This I have been led to believe is as a result of someone far east trying to copy International Rectifiers "Trench FET" design without understanding it and as a result getting the design completely arse about face. So what we have here is a badly designed circuit using badly designed components. Welcome to the world of really shite electronics.
if you burn up your room, the hotel will just replace it with another shoe box
isnt it safety hazard having so much packed rooms adjacent to others
I recovered a whole battery pack in this way. It was a Ryobi 40v tool battery back that had just been left to sit for a long time. I got it from the local Free Geek, a community electronics/e-waste recycler, and they thought it was dead because it showed such a low voltage. I snatched it up for a measly $5. When I measured, each cell was sitting at about .3-.4 volts.
First thing I did was remove the balance charger board and clip all the leads. The pack was actually two assemblies of 10 cells in series-parallel making 20v, so I just wired new balance leads onto each parallel string, and commoned the parallel strings together to make the entire pack 20v. I then took each parallel string and hooked up to the 3.3v output of a computer power supply. Monitoring the current, the four cells in parallel drew about 1-2 amps over a period of an hour, but which point they reached a high enough voltage where my Imax B6 hobby charger would tolerate them. I did this for all 5 parallel strings, then wired it all up to a balance connector and hooked up to the charger.
It works perfectly and the cells seem to have full capacity (I discharge-tested one of the strings of 4 cells and for 5Ahr out of it before I called it quits) so I have one hell of a 20v tool battery now. I went on craigslist and bought an old ni-cad powered 18v Snap-On impact wrench for $40 with dead batteries. Opened it up, wired a connector onto it that matched the one I'd wired to the battery pack (I used 4-pin molex connectors because I had plenty) and it works great! For $45, I have what is a functional equivalent to what brand-new would be a $700 tool.
I also wired up an old 18v reciprocating saw the same way and it also works great! I plan on getting a whole stock of old ni-cad tools to run off this battery pack.
Damn it Clive, I'm supposed to sleep man
Clive's beautiful boomy voice is often what brings me to sleep. I'll often have to watch his videos twice, once to fall asleep to and once to actually know what is going on.
Buddy Van Doodle with a welder, Buddy Van Doodle with a welding gun...
+Jane Doe Wrong channel, go to Pewdiepie for that
+Jane Doe, Wrong website, go to stormfront or infowars for that.
Jane Doe ok babe
Clive, with regards to samsung batteries, it was the ribbon coming out of the cell, before the protection circuitry, the traces were so close and yes you were right the battery didnt have enough room, the battery expanded a little and allowed the 2 traces to make contact, and, erm , boom?
The seemingly endless notebook.The Explosion Containment Pie Dish®.The Vice of Knowledge®.Random flames.All this and more on The Big Clive Show!Somebody needs to start selling "Explosion Containment" pie dishes, either as funny gifts or for the purpose of explosion containment.
He can do the same topic over and over but each time you learn something new and its always interesting.
Thank you for this video, perfect timing as i bought a RC hobby truck yesterday together with a 2 cell 7600 mah lipo. Makes me understand the battery much more
Thank you for the link to the article. Between it and your video I have a better grasp of the problem.
I work with LiPo racing drone batteries and what I learned is when over discharged, the capacity goes down and the amount of amps that can be given goes down. Along with this is more voltage sag under load. I experienced this when I accidentally left a battery plugged in and it drained to 0v. When I charged it up and flew it, the drone had far less punch, didn't fly as long, and the battery got quite warm. Keep in mind that the drone draws 80+ amps.
I've had the same experience as well. However in my experience its only 1 cell in a multiple S (series) pack that loses the capacity.
The voltage sag is most extreme on that single cell, effectively bringing the pack down to a "discharged" voltage while the good cells are still at their nominal 3.7 under load.
Not that it matters, in both scenarios it is the same effect on single cells but if you have this issue with a 2S+ Li-Po, you can salvage good cells or replace bad ones.
I've only just started tinkering with 18650's in the last few weeks. And I found this video right after i finished doing the same self-discharge test on over 60 18650 cells that i got from old laptop batteries.
I charged them, recorded the fully charged voltage of each cell, and then left them for 2 weeks. Most of these cells started off below 2.5V, others were even below 1.2V, and a few of them had a voltage as low as 0.12V.
All except for two passed just fine. And most of them seem to still have most of their original capacity.
Don't bother debating quality, Nature is a top tier journal. The number of batteries tested was 16. Low but the data was tight enough to get past the reviewers.
Now that is what is called an excellent video with knowledge and science backing it up. Well done sir!
This is a topic I wish I didn't know so much about, made me loose sleep at first until I had a full understanding. Even now their is to much to have 100% full understanding but I think I know enough to to sleep better.
The Samsung cells are more on the side of Li-Po packs when it comes down to the makeup chemistry and they are like a lot of newer packs because people want longer run times. Unlike the initial Li-Ion and Li-Po cells the nominal voltage is usually 3.7V per cell, with a max charge of 4.2V +/-0.05V. And depending on the chemistry of Li-Ion cells some can go down to 2V from a parasitic drain, but not while under load. Load minimal voltage would be usually 2.5V for chemistries like ICR and some other safer mixes. So this means the voltage cutoff is usually at 3.0V per cell when you measure it without a load and why they set the cutoff at 3V per cell.
Most cutoff monitor chips these days are also staying on the safer side of max charging voltage with 4.1V and not 4.2V for the sole reason of safety.
But back to my point, Samsung and some others are now pushing the Li-Po packs to 4.35V max charge per cell with a nominal voltage of 3.8V unlike the ones labeled 3.7V per cell. And the soft packs are easier to be punctured when they swell up by other components packed into these thin phones and tablets that release the volatile venting. They already become more volatile and unstable if they well and they are usually OK with the heavy wrap of PVC around the cells until they get punctured and that's when they "explode" or technically vent.
A safer Li-Ion 18650 chemistry Li-Ion like most Samsung, Sanyo, Panasonic cells take a lot before they would vent. But then you have the really cheap and fake cells that's a big problem on the market. With yours in this example I don't know what cell that could be at 1200mAh wrapped in blue PVC? I usually like to see a pink battery in these cheaper power banks like I've bought from microcenter for $5 US and had ICR Samsung cells. A cheaper chemistry cell will also build up these copper shunts a lot faster then a good known cell. I would still be carful with that one, unless it's a re-wrapped recycled 18650 that was torn out of a recycled laptop pack and re-sold in this power bank, yes that happens also. So you now don't know how many cycles are left for charging or how many times it has been fully discharged and what partial "copper shunts" are already built up inside the cell.
Their are so many factors and unknown variables when you buy the cheap lithium based battery operated things.
I usually recommend recycling any battery or charger that comes with the cheap LED flashlights or other cheap things and get a good knows 18650 maybe that has a built in protection if it fits in the flashlight and a good XTar or NiteCore authentic charger.
As for Samsung and big companies making this mistake, shame on them for not testing properly under real world usage how a customer would use the device, heat it up playing games, charge it back to back when it dies or gets low, run GPS with the LCD on full brightness while charging in a hot car and other scenarios or they would have realized they had an issue. They are so worried about beating the other company to the release of the new phone, or new" whatever" they over look the customers safety and skip basic testing that should have been done.
If your buying cells in the US I recommend www.illumn.com/ since they test the cells to make sure they have authentic products and have agreements with manufactures to buy direct with some.
Or check with the big flashlight forums since LED flashlight builders seem to make sure they get real cells and can recommend a good seller for your area. Vapers only seem to care about what people say and don't test the cells and want bigger clouds, no offense to those who vape. I've seen testing done on cells in vape forums that had wrong and horrible misguided information and wouldn't trust them to put a 18650 to your lips.
Be careful, some of these vape reseller sometimes buy fakes and sell fakes and don't even know it. Once they are told I've never seen them recall the fake ones. Illumn has had to recall a fake cell they sold once and stand behind what they cell and cares for the customers safety.
*Disclaimer, I don't work for them and I'm not associate it with them in anyway.
Have fun and Be safe, be careful to all,
Scott
Sadly as with most things technology and science, there is far too much hysteria and not enough education. Great to see videos like this, and the videos where you actually test what happens during failure!
Perfect timing! Just yesterday I stripped down some old laptop packs to harvest some cells for a silly project that neds 8 of them, so after sorting i have a load of cells between 0.7 and 2.4, I was going to bin the ones under 2v, but you've changed my mind, I'll stick on charge at 50mA and see how they fare... in an explosion containment pie dish of course.
I'm not sure whether or not this has been mentioned, but many 'Proper' chargers will not work if they detect a voltage of less than (say) 3.0V per cell. I usually fix the problem by charging in the NiCad 3 cell rate (per single Lipo cell) for a few seconds to bring the minimum up to a point where the charger protection circuits can be by-passed. Making up a charge lead using 2.54mm header pins allows one to charge individual cells of a pack via the balance lead. Only the most expensive batteries have matching cells and this is a godsend to keeping a well balanced battery.
over-discharged batteries are less volatile than a charged cell, it just poses danger of plating the cathode. So it makes some sense to over-discharge the cell until the electrolyte is not reactive to the air prior to shipping. It does leave the cell with a shorter life
Excellent video. Really enjoyed the theory behind these cells. Will watch again to soak up more info.
My experience with over-discharge:
200mAh Li-ion cell exploded, luckily it was small and in a metallic box.. The battery was all fluffy and the cap of the box had a black and smoky spot over the battery.
3000mAh Li-ion cell: forgot a 3.3Ohm resistance in parallel (I was making some complete charge and discharge cycles) and I forgot to remove it in time... 0.98V on the battery, which was "inflated" and pretty hot... Capped the hell out of me as soon as I've seen it... With a windproof lighter (very hot flame) I desolderd the resistance and immediately put the battery outside of the window... Luckily, this morning, it was still there, unexploded
I think it helps when the discharge current is low. A lot of the horror stories about puffing and exploding lithium cells seem to come from the RC world or other high discharge uses where the packs don't just get discharged past the recommended minimum but get hammered down there. With an RC battery and a moderate current draw the voltage has a tendency to fall off a cliff once about 80% capacity has been used, after that point the voltage plummets very quickly and damage can be done. Many people recommend to only use 80% of the capacity of a lithium RC battery. With lower drain cells like with phones and powerbanks that doesn't really happen so the voltage can gently trickle down till 100% capacity is used.
So I suppose it makes sense that a battery that's gently discharged past the recommended empty voltage would be less volatile than one that has been forced past under great strain.
Thanks, this video came at the right time for me. I just bought a power tool with a 12VDC lithium battery pack. The tool shipped with the battery installed and the tool's power switch was in the "on" position, so the battery only had 0.5 volts. After three attempts, I did get it to charge, but the battery pack was quite hot. I'll let it sit for a week or and recheck the voltage.
I have a few old laptop spare batteries around the house from rather old laptops that are not used anymore. Some have probably been sitting around for 10-15 years. I figured they were paperweights at best. A few days ago, I decided to take one of the older ones and perform a bit of surgery on it to see what was inside of it. Turns out that laptop battery contained 9 Sony 26650 cells. I stripped it apart into single cells. The measured voltage was very little -- anywhere from 0V to 0.5V. I tossed the plastic case and circuity and used some test ("alligator") clips to connect it to a generic cell phone external battery charger and let it try to charge the each battery. After a couple of days, the voltages are currently sitting at 8 with voltages anywhere from 3.97V to 4.20V and 1 with 3.84V. Another laptop battery yielded (8) 18650 cells in it with initial voltages around 1.0-1.5V and the end voltages ranged from 4.21V to 4.41V after charging. Another laptop battery yielded (10) NiMH cells that started out at 0V and 7 of them have currently been able to be charged up to 1.2V to 1.41V. My NiMH charger would not recognize them, so I just hooked 3 up in series and connected it to a low wattage 5V switching power supply and disconnected it when the voltage across all three got up to around 4.5V.
Now, I just have to figure out some use for all these lithium ion and odd size NiMH cells. :)
Wrong Clive. When my lithium batteries discharged to 0v my brain exploded.
I have almost this same power pack. I took it apart because the mini USB plug would not go in the socket completely. Just checked it and the battery had discharged it self from 3.9 volts to 0.07 volts, don't think I'll be trying to recharge it now. Thanks for the video Clive!!!
I salvaged a bunbch of laptop 18650s for flash lights even as low as 0.5v seasm to recvover just fine I have soem that are 5+ years old and still hol,d near 90% of capacity and dont discharge. But i also have ones that were 3v and are useless at 100ma capacity.
KingOfKYA Same, I've seen absolutely no correlation between the voltage I get them out at and their final capacity. I test mine at a 1A discharge from full down to 3v, and keep 1.75Ah or better. I've got a vid on my channel of an arduino based 4 cell tester, unfortunately I lost the sketch :/
Luke Den Hartog Sad that you lost the schematic, but I've been using these:
www.amazon.com/gp/aw/d/B015LB8DFG/ref=mp_s_a_1_1?ie=UTF8&qid=1500093891&sr=8-1&pi=AC_SX236_SY340_FMwebp_QL65&keywords=BT-C3400
PV2Omni Damn thats expensive compared to what I did for mine. Mine also sent debug data over the serial port which was handy. Its the arduino sketch that I'm missing. The schematic is super simple, resistors, mosfets, and some leds. Being able to do four batteries at 1A per cell discharge was really handy for processing quite a lot of cells a day. I've also got a 10 cell charger based on the TP4056 which has a temperature cutoff pin, which came in handy for the cells that decided to get really hot.
Luke Den Hartog Yeah, with costs going down on components; if you know what you're doing, and have the time, you can make it cheaper. Not always though, compared with things directly from China.
PV2Omni also this is a niche market and hobbyist can make way cooler and more functional products.
Thanks for the incredibly informative video Clive! I've recently inherited some old Dell battery packs, so I'll be sure to apply this to the 18650 cells.
I recently pulled a 7-pack of 18650s from a discarded cordless vacuum. One cell showed -0.16v, so I didn't dare put that on the charger, but the others had varying charge states and I managed to revive them all right. Time will tell when it comes to retention, so fingers are crossed.
What I found taking apart laptop cells is they will read .7v or such but that isn't actually the battery charge but what seems to be a leaking voltage from a protection circuit on top of the cell.
As soon as I connect it to a bench supply and power it a few minutes it'll shoot immediately up to more of a standard operating voltage and usually work fine from there on out.
Below 3V lithium cell voltage plummets. If too low it should be brought up slowly with a trickle charge to 3V again.
I remember making a power bank, I used one of those power bank circuit boards (from 5 below in the USA) and had a pack of about 8 18650's in parallel. I was attempting to solder it together when I put the positive and negative across one of the little chips.
After that, the chip went to over 176 degrees F (80c) and shut down (thermal cutoff?), it would always come back but it never worked right after that.
Are you sure you weren't a puppeteer for Sesame Street in a past life? Your hand motions are a dead give-away for the Swedish chef. Love your vids. You should get together with Sorin: DIY Nerd. Would be a great time.
Seams to be two types of this very power bank from Poundland you have here Clive (Poundworld now do a 2400 version for £4), as I found out the past week (As in new / current stock), and the last three of these I have had, all are dead, will not take a charge, and had this arsey sales assistant trying to argue to toss with me, till I explained that they are supposed to have some minimal usable charge so you can check to see it at least works, due to the nature in the way the batts are, otherwise damage can possibly occur.
Did finally get one (Could use with a few more), and been watching a few vids on line, about reconditioning laptop battery packs, and so happens I have one from my HP laptop which takes bugger all charge, but found all the batts are sitting at 3.5v, so chucked one of those in to one of these powerbanks, and now quite happily charges my phone when I am out and about, so a nice cheap powerbank, which although will not 100% charge my phone, is good enough to get me out of a tight spot.
I read the article in the link: it seems, that the most dangerous thing is over-charge.(the article doesn't address that) It's interesting to know, that I can make the voltage balancing system part of the charger, and it's fairly safe to discharge, as long as no cell is allowed to drop below 0 volts. I still cut them off at the knee,~2.3-2.5 volts, depending on load current, just for the sake of longevity. just as possible as it is to reverse charge a cell in a high voltage battery, it's easier to over-charge a cell in the same string. The real problem lies in differences in self discharge rates, especially, if the battery has been in storage. That makes it VERY easy to over-charge cells, without a battery management system, to protect cells from over charge.
Please do a demonstration on over charging a cell at a very LOW current. It's obvious what happens, if a cell is deliberately overcharged at high current, RUclips is full of videos showing that. I would like to know what happens inside a cell, that has been "trickle charged" for too long.
Extremely useful video. I was curious about this topic for quite some time and wasn't able to find the satisfying answer. Thanks. I had a similar experience, I was able to recover zero volt cells, and they just works fine, no issues whatsoever.
How or what do you use to get an overhead shot of the bench when you're traveling or someone else?
Improvised shelves.
I have one of these power banks and Clive failed to mention, these operate the 3.7 to 5 Volts inverter 100% of the time, I re-charge mine every day. That is why they are fully flat when you buy them. Mine is PINK. (Mine was $2 at Goodwill)
Many draw a tiny amount of standby current and just pulse every so often to keep the 5V output topped up. They should last for months in standby on a full charge.
If the cell has internal protection, like a lot of 18650 cells do, the voltage may read zero simply because the internal protection has cut out due to low cell voltage and all you are measuring is due to leakage through the protection chip. When you charge it back up the protection circuit resets.
From what it looks like to me if I didn't know any better it looked like the battery has a protective 'cap' on the + side. If you were to compare it to a standard unprotected 18650 cell and it is the same height then it's unprotected. I say this because I've messed with Panasonic cells, in both their 3400mAH unprotected green cells and some from an old Toughbook and the + side looks just like you'd see on a standard AA battery without the 'ridge' or 'ring' and a pronounced terminal that's not flush with the battery.
The thing about the protections, in both those batteries in the Li-Po batteries for MP3 players is that the reported voltage isn't the same as the internal voltage of the battery. In fact, most service manuals I have for my laptops (non-Panasonic) state that a battery pack that registers at 0.00V is not faulty it's just in a sleep mode.
Definitly going to read the document, thanks. My experience with overdischarged cells is slight capacity loss and higher internal resistance, which makes the cells rubbish to use.
Drawing a too high of amperage out of a lithium cell is what usually destroys them. As you demonstrated with the jump start pack.
Thank you for the video. It pretty much sums up with a good explenation what i have been doing when scaveging laptop batterys.
Put a charge on then, if they have
I've revived tons of fully discharged cells in the past 10 years, as mentioned most of them are doing pretty good, just with slightly reduced capacity but more importantly higher internal resistance, so they aren't good for being discharged at 10C or so anymore (assuming they were in the first place, thinking of lipos used to power drones)... in a powerbank or powering accessories no issue. Some lipos do balloon and die though.
So it's safe to charge them to -12v right?
Bigclive you might want to get a little "bill examination microscope", I bought one and they're perfect for reading SMD component markings. Some have very bright white LEDs for enhanced lighting, and mine even has a single UV LED for essentially bill authenticity recognition. Some SMD markings actually glow under it.
I love how these Dixies sound from the inside :P
Never the less, awesome video!
i have a really puffy 4s pack, its dropped from 5000mah to 4700mah, i wont throw anything, its one half of the wife's daily use ebike battery pack now lol...
Whats the other half you wonder? the 4s pack i drove over in the dark with the van, its not square now its like a roll.....
issue is when you have series cells and just a simple low voltage alarm, if one cell is dropping faster than the others, once it gets to like 2.75 it will fall like a stone to 0, and then the other cells in the series chain will push it into a negative charge, then once this happens the voltage of the overall pack is low enough to trip the low voltage warning/cut off, but for that one cell its too late.. then you plug the entire pack back into a charger that the toy or whatever came with, and the fun starts...
Yes that was the documented problem with samsung, they compromised the allowance area by putting form over function. They had no adequate safety space.
As for the battery, it's an old trick to put it onto a charger in nimh mode on the lowest charge (0.1V) and trickle it up. All of this battery info comes from the RC community. :)
Recycling dicarded non-medical inhaler Li-ion cells that have been subject to overdischarge. Using the built-in chargers from the rechargeable versions of these inhalers, the minimal circuitry checks for the cell's ability to carry a certain amount of charging current, continuing to charge if the criteria are met, or switching off if charging levels are too low. Under normal use the built-in LED 's forward voltage limits the voltage down to which the cell can be discharged. However discarded device cells can even be found with zero or even negative volts (how can this happen? ), especially when the discarded item exposed to the elements, where condensed water can result in continued discharge below designed cut-off voltage. Overdischarged cells can be charged in parallel with cell discharged to acceptable voltages like 3.2v, since the max charge voltage is set to something like 4.13v on the charger circuit, and the fully discharged cell can be forced to accept a charge at this voltage over time and the charger can then kick back in. Just take suitable pie-dish precautions when charging potentially dodgy cells and don't use them for mission critical situations like attack UAVs
With over-discharged cells it's usually better to gently bring them back up to 3V with a low trickle current. After that they usually recover quite well.
The other known issue with the Note 7 batteries was the battery thermal sensor, it never reported on temperature so when the phone was charging the battery went into thermal runaway and burst.
[Mobile Phone Repair Technician]
Poundland Camden high street..bought one..tentatively charged..flashing light didn't go out as per instructions..gave it 4 hours on a switch mode power supply behind a screen..don't feel able to trust it to charge phone though it is useful for my bendy led usb..nice one mate
Great video, man! I have been reusing cells from discarded notebook batteries and the first one I ever opposed the voltage of the cells were 0.64v, but I tried to recharge anyway. And all of them stayed above 4.1v until today. (I didn't use them yet - I plan to make a 6 cell power bank with them.) Later, when I finally got a capacity tester, I discovered the those 6 cells have more then 2100mAh! So, the initial voltage really means nothing.
I discovered recently that several of my power banks had discharged the cells to below 1v so good to know they should be ok/safe - thanks :-)
btw - I have now fitted a toggle switch to them so I can disconnect the battery when not in use to stop it happening again
I've bought a few of these. My front light on my pub bike takes them. It came with an adapter than can take 3AAA's which do not last long (kodak). The rechargeable they sell are useless. But the 18650's, i wipe them out nearly dead, but they always work for me and re-charge and they are only a pound. They do better and i always have spares.
The problem with samsung batteries was purely a case of pushing a technology passed the breaking point. You can only squeeze so much capacity safely into a small space, and samsung clearly exceeded that. The issues with them had to do with thermal runaway, there wasn't enough space for the cell to dissipate enough heat, and once it got just hot enough, there was no stopping it. Squeezing the cell made it even worse, which is a double hazard, cause that will normally only happen when in the pocket.
I'm sitting with 200+ Samsung 26F 18650s on my bench atm, recovering them from 0.2-0.8V and capacity testing them. They're rated at 2600mAh and is coming in at 2350-2550mAh. Which is plenty good enough. Only remaining thing is to test for self discharge. Going to leave them charged for a month and see. :)
This confirms what I've heard before - the real danger of damaging the battery is is reverse charging the cells. Not normally a problem with a single-cell pack, but as issue with multi-cell packs. Even then, I think there's a difference between discharging with a load and self-discharge. If a battery self-discharges, it's unlikely to develop a reverse charge on any of the cells.
In the Methods section of the referenced Nature paper the researchers used an 'explosion-proof chamber' whereas the correct BigClive approved approach would be to use a pie dish :-)
The Note batteries were growing spikes at both plates. Due to high current charging & discharging this caused a short, which caused an overcurrent which caused fire.
Same thing for those cheapo hoverboard-batteries.
When do we get to see this massive heat incident you speak of?
Your timing is impeccable I have to disassemble an 18650 pack today which is 4 in parallel and 4 in series (16 cells total) in order to find out why one of the sets of 4 cells is dropping voltage; hopefully it's just one cell dragging the other 3 down.
Why is it that they just seem to fail from time to time?
I kept waiting for the lithium battery taste test but it never came☹️ Very informative Clive. Thank you for this video!
I had never considered reverse charging a cell in a pack as a result of continued usage after depleting one cells capacity.
I once bought a parts car real cheap because no one could figure out why the starter wouldn't work even when replaced with new. When I went to check the voltage I found that the polarity didn't match the terminals. Apparently someone had drained the battery and then reverse charged it. Everything worked except the starter and wipers were running backwards. I turned the lights on and left it overnight, charged the battery correctly, started it up and still drive it today. That battery lasted about 4 years even with the abuse it had seen. I never would tell the seller how I fixed it other than say it was his own fault.
Mike (o\!/o)
Li.Po cells are not the same as Li.ion cells and behave differently. The referred research is about lithium-ion cells. A lithium-polymer pouch cell will puff up when stored at low cell voltage, without ever being at a negative voltage. Being puffed up, its internal resistance will rise and it will be unsafe for high current applications, especially when in a series pack next to good cells.
For high current LiPo packs, I recommend using those cell monitor alarms that connect to the balancing connector of a pack. It will alarm if any of the cells goes below the set minimum voltage.
For low current lithium ion packs, a reverse diode over every cell might be able to prevent -12% SOC for the individual cells.
I could be wrong on this but I seem to remember the earliest lithium cells (back in the 1990's) were nothing like as robust as anything I have seen in the last 5 or so years. It could be those problems used to exist but solutions have been found a while back. That said SAFT give fairly strict instructions not to over-discharge on their web site on the application notes. I think though it is more a "loss of capacity" issue than anything else.
nice informative video, just as relevant as it was 4 years ago.
I have a stockpile of 'dead' laptop batteries (18650 cells, between 3 and 6 depending on laptop brand) from work that I'm waiting to open and see if any of the cells inside are still useable.
In the laptop it will go from 0% to 100% in a few minutes, but then immediately die when disconnected from the power supply.
Please note that Lithium ion batteries should NEVER thrown in the trash bin. Please send these batteries to a hazardous waste disposal as even a dead one can still cause fires.