Risks of salvaged 18650 from laptop batteries  - Page 1
Forum section: electronics / beginners

author: Dhanushka
author_rank: Regular Contributor
timestamp: August 19, 2019, 09:52:31 am
content: Dear all,I brought a laptop battery to salvage few 18650 batteries. This battery pack was a cheap replaceable one and this was not used by anyone. But when I open it carefully there was a nasty tight smell inside but there was not ant leaked liquid. However I did not care about that. But the spot welded places have corroded of 4 batteries. Only two cells could be salvaged. These two cells has no any nasty smell or corroded places but other 4 had. All batteries were at about 0 V. I recharged the good two batteries with TP4056 module and that was bit successful as I think because that charged up to 4.2V and current through a 0.47 ohm (printed value) resistor was 5 amps. But the voltage drops about 0.010 V per day.My main questions are,1. Is the self discharging of this cells normal?2. Are these batteries safe to use?3. The nasty smell can make a health problem?Thanks

author: sleemanj
author_rank: Super Contributor
timestamp: August 19, 2019, 10:03:58 am
content: Any with corrosion of course throw away0v, some will say throw away, I will say OK, IF they hold charge AND you charge safely (don't charge somewhere that fire would be damaging)5A discharge is way too much for salvaged laptop cells though, I'd be surprised if that is even in their new specification a 5A discharge on a typical laptop cell would be less than half an hour battery life, they are not designed for that, keep discharge to 1A (and charge).0.01V initial self discharge from the 4.2v top-of-charge would be OK, but it should level out, if it keeps discharging such that it goes below 4v from a 4.2v charge, that cell would be questionableThe smell, well, don't go huffing it, but I doubt it's particularly harmful for an occasional exposure, bigclive has opened lots of cells and he's still alive.

author: kripton2035
author_rank: Super Contributor
timestamp: August 19, 2019, 12:19:57 pm
content: lithium vapors are toxic at high dose. manipulate them in a well ventilated area it should be ok. in pro shops for batteries, you need a very powerful hvac for these.

author: Rick Law
author_rank: Super Contributor
timestamp: August 19, 2019, 05:35:41 pm
content: Quote from: Dhanushka on August 19, 2019, 09:52:31 amSince you are testing it at such high amp, are you planning on vaping with it?Even with "new" batteries, horror story is plentiful when placed so close to face and body with vaping. I don't do that kind of vaping, but if I do, I would only use best battery money can buy. Those big multi-18650 typesseemto sacrifice all other aspects (including safety) in order to get very high-amps; particularly with some of the mods they sell - all to draw even higher Amp. I am sure thousands are using that every day, but I also am sure that there are "once in a life time experiences" that one rather not to have...I do use e-cig, but for safety, I use one designed to use a small 200mAH battery. Too small to blow up big time so damage is limited.As said, plenty of horror stories, here is one for example and he is using anewbattery:Example from UK:https://www.dailymail.co.uk/news/article-7340519/Driver-engulfed-flames-left-degree-burns-vape-EXPLODED.html

author: KL27x
author_rank: Super Contributor
timestamp: August 20, 2019, 01:07:51 am
content: QuoteNot normal for a good cell. A good cell charged to 4.20 can retain that for one the order of a year, maybe several, before dropping to 4.19V.An older cell might drop at first but stop at some point. Maybe 4.15ish.QuoteDepends on what you use it for, and what is your definition of safe. They're definitely damaged, because they were 0V when you started. And you fast charged them from that state. They're obviously damaged goods, but again. It depends on what you wanna do with them. A cell venting hot gas and flame might be no big deal. For low current, low charge stuff, in particular, it might actually work ok, for that; I suspect your cells have a high internal resistance and won't be very good at high discharge application; they might have very short life and get hot. But that's for you to find out.Quote

author: james_s
author_rank: Super Contributor
timestamp: August 20, 2019, 03:53:57 am
content: Li-ion cells really don't like to be deeply discharged. I would discard any that were discharged to 0V, there's a reason the protection circuits are designed to prevent deep discharge.

author: amyk
author_rank: Super Contributor
timestamp: August 20, 2019, 11:56:43 am
content: 0V is actually fine, but if they were in reverse polarity for any length of time then they'll really be damaged:It may be something other than the electrolyte if it smells awful. In any case, it's not a big problem unless you deliberately inhale lots of it.

author: Gyro
author_rank: Super Contributor
timestamp: August 20, 2019, 04:07:44 pm
content: Interesting, so it's the same weakest cell polarity reversal that results in damage to most other series cell battery chemistries then (including NiMH and leaking alkaline primary ones).That's rather reassuring, given that many small rechargeable Lithium applications just use a single cell. Obviously no help with drill battery packs etc. where it means that you have to set an artificially high end-voltage.

author: tunk
author_rank: Super Contributor
timestamp: August 20, 2019, 04:50:41 pm
content: Unless they are rusted through the casing I would try to charge the four othersand see how they behaves.I have salvaged some cells from used laptop batteries. I have looked up theirspecifications and IIRC the max dicharge current generally are 3-5A.

author: james_s
author_rank: Super Contributor
timestamp: August 20, 2019, 08:36:00 pm
content: That is interesting, helpful to know.Still, if some of the cells in a pack are physically leaking that does not give me a great deal of confidence in the state of the others. Given good 18650 cells are not terribly expensive I think I'd just get some better ones unless you absolutely need to make these work.

author: KL27x
author_rank: Super Contributor
timestamp: August 21, 2019, 04:49:20 am
content: Quote0V is not the end of the world. If you trickle charge it back to around 3V with something like roughly 1/20th C. If you charge this dead 18650 with something approaching 5A, as the OP has desribed, that's over 1C, in the least. Do this, and the plating doesn't go back on, evenly, and this increases the chances of damage to the internal dielectric. This can lead to leaks and internal shorts. The latter, of course, can lead to cells unexpected turning into a hot potato and venting hot gas and flames.There's relatively little energy left when the cell gets down to 3.0V float. It's not worth getting any more out, then having to trickle it back in to recharge. Also, you might expect to reduce the life of the cell when you discharge much under 3.0V, even if you trickle charge.*So yes, I agree. 0V is perfectly fine. As long as you watch Clive's entire video and don't fall asleep.** I'm sure he explains this.*I would assume any lumps and bumps that form over time tend to get only worse. If it were possible to discharge to zero to dissolve lumps and bumps, then plate the material back on smoother than before, I think someone would be making batteries that can be reconditioned in that way. If you reduced the amount of electrode material to the point where you could dissolve all the lumps by deeply discharging, I think the bare areas would not plate back. Hence, one way trip towards shitzville. If you discharge beyond 3V, the amount of electrode material that migrates is very great for little return. And Humpty doesn't go back together again as good as he started. Avoiding reverse polarity is a good idea. But we stop at 3.0V for efficiency and for #charge cycles of safe operation before leaking, lower capacity, and risk of internal short.That's ~3.0V float. Under heavy load, it might be closer to 2.5V, where you want to cut your losses. Off-the-shelf voltage detectors made specifically for this task seem to bottom out at 2.7V, but we don't necessarily need to follow industry guidelines when we have our own design, life expectancy, and safety goals; we can make our own beds and take our own chances.The fact OP's cells are self-discharging so rapidly, that is obvious sign of internal damage. They're a baby step away from internal short and possible meltdown. Even if the internal resistance is still good enough to run the laptop, it would no longer be a good idea. At least from the perspective of the laptop manufacturer's liability.**And what the chances OP reads this far without falling asleep? Easier to just tell him his cells are damaged.