Using lithium battery which was below 2.5v - Page 1
Forum section: electronics / projects

author: c64
author_rank: Frequent Contributor
timestamp: December 12, 2020, 05:51:05 am
content: Most resources say lithium batterymaybe permanently damaged if left to discharge below 2.5v.So, let's suppose you have a battery which was stored discharged for few years and now the voltage is way below 2.5v. Let's suppose you charge it (with very low current) and it appears to be working. Does it mean it's not damaged and can be used without danger of catching fire?

author: Hiemal
author_rank: Regular Contributor
timestamp: December 12, 2020, 05:55:36 am
content: I'd say as long as you're not doing anything like, ridiculous with the battery it should be fine. No high discharge or fast charging, don't throw it against a wall, etc. It's internal resistance is probably quite a bit higher than it originally had been. Probably lost capacity too.buuutttttLi-ion batteries really only catch fire when they're horribly mistreated from what I understand.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 12, 2020, 09:09:32 am
content: Overdischarge counts as "horrible mistreat", especially if it's near to 0V (say below 1V).All bets are off.Very slow charging, say at C/100 for a few hours, then see if it holds the voltage, or if the leakage current has severely increased.Still, the risk of copper dendrites shorting the cell internally will be high. Then it only depends on the passive safety level of the cell whether it causes a fire or not.The Right Thing To Do is to dispose of it and find the root cause why the circuit overdischarged it in first place and fix that circuit design.If it was stored discharged (so, assuming OCV somewhere over 3.3V) without external circuits connected and it went below 2.5V on its own, it was a failed cell to begin with, just dispose it and buy proper cells.

author: tunk
author_rank: Super Contributor
timestamp: December 12, 2020, 01:57:36 pm
content: I've seen 18650s below 2.5V turn out ok, with very littleself-discharge and maybe a 20-40% capacity loss. Haven'ttested internal resistance though. I've also seen the opposite.So I guess the only way to find out, is to test the cells.To get a low charge current, you could place a resistor inseries between the cell and PSU.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 12, 2020, 02:02:19 pm
content: The tell-tale sign of there being a problem is the increase in self-discharge current.It's hard to measure though unless you have months of time.Charge it to a known voltage, measure after a few days after surface charge has bled, then let sit for a month to see if the voltage drops any further.The only robust and safe thing to do, though, is to replace the cell. Low self-discharge doesn't guarantee the lack of copper dendrites.

author: c64
author_rank: Frequent Contributor
timestamp: December 12, 2020, 10:21:15 pm
content: I should have mention where the cells come from.I have bunch of old laptop battery packs. Probably ~ 10 years old. I haven't touched them for few years and now decided to open them to harvest the cells.Couple of cells are at 2.5v, and lot of them are in the 1.2v-1.8v range. Some are below 0.5v and I already discarded those.Of course I would rather get brand new cells, but I don't know any reputable source to buy cells from

author: rmlazzari
author_rank: Contributor
timestamp: December 12, 2020, 10:59:08 pm
content: Hello, I had this same question some time ago. I managed to recharge the battery using a modified TP4056, to keep the current at 130mA. It took something like 20 hours charging until it reached 4.2v. But in practice I was unable to use it, it no longer retained the load, that is, it was no longer useful for anything. So I disposed of it in the appropriate trash and... good bye.In Brazil, especially in the capitals, it is not difficult to find good 18650s like Sanyo, Panasonic etc. Even so, I was already deceived when I bought a battery that promised "paradise" of 9000mAh ... The best batteries reach real 3000mAh or, at most, 3.300mAh. I believe that in large cities in Australia such batteries can be found, perhaps in regions of electronic commerce, even.Good luck!

author: sleemanj
author_rank: Super Contributor
timestamp: December 12, 2020, 11:05:55 pm
content: I've done the same as you, harvested from packs that sat for however many years in the shed.Most of them recovered just fine to useful capacity (some were still good for over 2Ah) and no notable self discharge, regardless of how low they were. I started out discarding ones below 1.7v, but out of curiosity I tried a few that were lower and some of those were also still useful.This is a few years ago, they still provide service to me in low current things.First charge I did at... 250mA from memory, in deep metal container with a lid, just in casehttps://www.kmart.co.nz/product/washing-powder-tin---grey/2868823

author: Siwastaja
author_rank: Super Contributor
timestamp: December 13, 2020, 08:01:10 am
content: Quote from: c64 on December 12, 2020, 10:21:15 pmOkie dokie, so they weren't in storage - they were connected to a crappy management IC which overdischarged the cells. Typical in laptops some 10 years ago.It's possible the ones above 1.0V are salvageable. 100% safety cannot be guaranteed, so you do it at your own risk.Slowly charge at C/100 for a few hours, see if the voltage rises and if they hold the voltage.

author: poorchava
author_rank: Super Contributor
timestamp: December 13, 2020, 10:34:20 am
content: I do some custom large scale rigs for testing used Li+ cells (think batches of 50k+ pieces). If they test fine (take charge, hold charge, do not explode during test and have proper internal resistance and capacity) they are fine. Never heard of a false passing test, where the end customer received w cell that failed horribly because of some random mistreatment in the past. AFAIK most of the cells I had to do with are from laptops and (sometimes) power tools.

author: enut11
author_rank: Super Contributor
timestamp: December 14, 2020, 06:00:28 am
content: Quote from: c64 on December 12, 2020, 10:21:15 pmJaycar sells 18650 Li cells with or without solder tags. I have also purchased second-hand cells on-line from sellers who harvest and test for capacity so you know what you are getting.The only meaningful test, besides capacity, is internal resistance. IR meters are expensive but you can get a good estimate by loading the cell with a resistor, eg 3.9 ohm, to draw the rated current (~1A). The difference in voltage before and after the test divided by the current is a rough estimate of IR.enut11

author: Peabody
author_rank: Super Contributor
timestamp: December 14, 2020, 03:29:57 pm
content: TinyCircuits, previously featured on The Amp Hour, sells a flat top unprotected 18650 on Digikey. 2500mAh for $5.95:https://www.digikey.com/en/products/detail/tinycircuits/ASR00050/9808766They've sold these on Digikey for several years, so I would expect they are prettty good.