Hello,
I just pull some 18650 from an old laptop. The batteries are samsung. This battery pack was not charged for almost 5 yrs.
Is it safe to recharge and use it?
I put a few on the charger, it charges for a few seconds and became full. But once I took it out and put in the charger again, it charges for 5 hrs. before it stop charging.
I do not have a meter to check the batteries.
You really need to get a meter to test these batteries before trying to charge. You can pick one up at a harbor frieght for less than 5 bucks. Its a small price to pay for your safety. Once you get one dont charge any 18650s that have less than 2 volts is what I think the common consensus is. Anyone chime in if im wrong. Good luck.
2.75vdc
If while charging Li Ion batteries get VERY hot to the touch…don’t use them
P.S. these recovered 18650’s from laptops are the bread and butter of us flashaholics…as long as you are running stock or sub 3A~ current lights…once you tweak and get the hotrods, the high current ones are recommended
I am gonna recycle them. Not worth it.
You are correct, it appears they have updated that particular part of the website and that part seems to be gone or moved
Last updated 2015-11-05
here is another part of that site that helps prolong Li Ion…not sure why the 2.75vdc part was removed
Found it…apparently the number is now 1.5vdc for over a week
They have added ALOT of great new info at the battery university
ok…then do you have links to the experts??
The internet is full of experts with no credentials. Heck I’m a self proclaimed expert on everything just ask me. H)
Yep being as im a self proclaimed expert on everything myself, I can confirm that Willie is indeed a self proclaimed expert on everything
If it’s on the internet it’s gotta be true 
I've put this together after searching through many threads on laptop pulls.
1. measure cell voltage. if it's less than 2.2v, recycle.
2. charge the cell. if it gets hot during charging, recycle.
3. measure cell voltage off the charger after 60 minutes, if not 4.2v +/- .05, recycle,
4. let sit for 24 hours and check again, if it drops by more than .1 volt, recycle.
5. discharge at 1 amp with hobby charger - if capacity < 75% of marked capacity, recycle.
Laptop pulls from brand name packs are pretty good quality batteries, and good for anything that draws up to 3 amps.
Hello, don’t want to start a new thread.
Are the cells good if it drops to 4.05v after about 1-2 months of storage?
i would think so…
Should be fine. If you have several, you can charge them up and then wait a couple days to see if any have self-discharged significantly. As mentioned earlier, it is a good idea to monitor the charging to see if any of the cells get hot. Warm is OK, but if any get noticeably hotter than the rest while charging, they should be tossed (recycled).
Also, be aware that some laptop cells are 3.8v (charge to 4.35v) as opposed to the more common 3.6v/3.7v (which charge to 4.2v).
If you are not sure what you have, post the numbers off the side and/or some pics.
If you still don’t have a DMM, you might consider picking up an Xtar VP2 charger. It has the ability to check resting voltage, and can also charge the 4.35v cells. 
I use a VC2 and like it, but the readout shows either “0” volts or next “3” volts at the bottom so unless a cell has 3V you don’t really know exactly how low it is. A voltmeter is an absolute must when working with LiIon cells!
Even a cheap one will let you know when you’re nearing too low to safely charge though I’d add some safety margin if I wasn’t sure about the meter’s accuracy. If a resting LiIon cell is 2.0V or higher it is usually safe to charge and use, but best to not intentionally discharge that low. I aim for 3V minimum and I’m not concerned if I go as low as 2.5V. Others will have different recommendations but generally this is a safe range to work with.
Phil
I agree that you should have a good DMM regardless.
However, the VP2 (not VC2) is actually pretty accurate, and will read resting voltage down to at least 1v (the lowest cell I’ve measured with it was 1.04v). Much better than the VC2 IMO.
Ah, my bad. I had misread the “P” for a “C”. Time to have a look at that model as my VC2 is my only LiIon charger and my usual luck means it will fail if I don’t have another one. That’s also a good excuse to buy another light!
Phil
My guess is deal grabber has gotten himself a volt meter if he’s asking the question …is a battery that has been charged full and has dropped to 4.05V in a month or two safe …
I’d say 4.05v is a pretty clear indicator that the cell is right on the edge of bad…At 4.0V there is no question i’d be tossing it .
If i didn’t have a lot of cells maybe I …wouldn’t recycle it right away but.i’d Be looking at new cells or new oem unused laptop packs
the price and availability of cheap cells from vendors like gearbest or bangood have almost made searching for good laptop cells a much less attractive option .
as i acquired more (mostly 18650) cells, the older, or the less capacity, or the less desireable cells? go to less used and lower power lights… my “better” cells end up in newer, more powerful, or more used lights.
anything that charges and holds power and provides safe, useable meaningful runtime in something? still gets used.
theres usually SOMEthing laying around that can use it, even if i have to remember and dig out an older light i normally wouldnt even dream of laying around with a battery in it. If all i DO is keep a battery laying in it, and only use it when i am sitting right there, at least its used a little.
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theres the occasional GEM doing this… i “blew” an old light, an 802 style light… then got into aspherics. I never thought i would like the light much anyways… on a WHIM i threw a battery in it, and LOW still worked…
the reflector only getting 120ma of power? still made the light USEFUL around the room and yard enough, i realized i actually LIKED it, and that it deserved a driver upgrade.
if i tossed any batter that wasnt OCD approved? i wouldnt have “too many” laying around… i wouldnt charge up unloved batteries for unloved lights and leave them laying around. SOmetimes? i “rediscover” a light i used to like, and end up liking it again.
There is enough of a difference between dangerous and “like new” that for a lot of us, “OK” is just fine, for lots of jobs. To be clear dangerous cells should be recycled, but cells with less then 2x the new resistance still can do a lot of work. at 3x I find them marginally useful and at 4x they are pretty much dead.