Individual 18650 capacity formula? | Best brand laptop battery for 18650 cells?

48WH/11.1V=4.32AH

4.32AH/2=2.16AH

implies 2200mAH cells

and it's 3S2P.

Apparently my Low-Alcohol Warning Alarm isn’t working.

Thanks for the correction.

Right, I haven't seen 2150's yet so went with the closest size I've come across.

Believe it or not, I re-wrote that part something like seven or eight times, trying to come up with some unifying formula. I kept stumbling over second-order unknowns like the current draw and residual capacity at the low-voltage cutoff (and that nagging low-alcohol warning) … But that kept me from seeing all the other, more sensible posts.

Plus, it turns out, it’s hard to find a pack rated in “Wh”. The ads may say that, but the labels on the packs mostly seem to give V and mAh, which is much easier to compute. But why would any of that matter since I know I’ll get a different runtime out of my “xyz” cell than you will of yours, even from the same batch, just because we use them differently.

Then the magic mushrooms wore off and it dawned on me, the OP is probably just looking to buy a pack to rob, with the deepest cells in it, & needs a way to tell which is which. That’s the only thing that makes sense, with the “YMMV” rule in effect.

So, just to kick me and my dog :bigsmile: (just kidding), would you concur that, given the different rated pack voltages, wouldn’t the “plain” Wh ratings (or calculation) of packs serve to show which has the deepest cells?

I’m not sure it matters at all to me. As long as laptop packs die, I will continue to churn these freebies “with extreme prejudice”. But if a fellow had to buy the best pack available as a cell donor, it would be handy to have a way to pick the best.

…

Dim

Went back to the computer repair place today, didn’t exactly hit a gold mine but I did walk away with 1 6 cell Dell battery. A bit of butchery later, and I got 4 cells reading 4v, 1 reading 1v and 1 reading 0v.

They are grey LG cells.

I asked the owner to hold on to any laptop batteries he gets in, he didn’t seem to think they got many in but agreed all the same.

Beginners luck?

I was at the Lowes return desk today to return a lamp. That area is were the recycle bin is. I reached in and pulled out this. I only took the one, what am I a pig? :wink:
Anyway here are the pics, no words are necessary. I am charging them up as I post this.





You need a bigger hammer!

:beer:

Edit: “Fukushima”??? Them is NUKULAR Batteries!

(Seriously, nice find! Those US18650GR’s have been reviewed here. I have a batch & love ’em.)

No pain, no gain, dchomak?
Don't worry... with bleeding... the blood will always stop... one way or the other.

Hope you didn't get hurt to badly.

Anyways: For your cells: 4400mAh, 6 cell, 2 parallels.
[(4,400mAh x 6cells) á 2 parallels] á 6cells = 2200mAh min capacity per cell (Actual min capacity 2291mAh per US18650GT's thread)

I got a New Dell cell origin Korea (Only korea cell: LG) Extended battery coming. Thinking it will yield 3000mAh Pink LGs. Will post once it arrives.

Does anyone have any info on which brands will come from a cell origin? Like LGs from Korea.

What comes from Japan?

You could say I’m on the “bleeding edge” of technology!

I hope everybody knows to keep some superglue (old-style runny liquid if you can find it anymore, instead of gel) on hand for when that happens. Works great. It sets almost instantly when it contacts blood. Dribble some down inside the cut, squeeze it closed, then get back to work.

I thought Samsung was Korean.

Wear gloves!

Samsung and LG are Korea

Panasonic , sanyo and sony are Japanese

Moli is canada and DLG is china

Almost every(New unused OEM) laptop pack I've torn apart have been pretty high end quality cells

used recycled laptop packs need to be viewed as a much riskier option

unless you have the right tools to assess the quality of the cells tou should assume they are much more dangerous than //new unused or protected.

obviously avoid all ultrafire /trustfire ...fire/fire batteries

I’ve been very busy lately but today I decided to check the forum. I was going to post a similar thread. I have a couple of batteries that I pulled from around five laptop packs and to my surprise only one of the packs had all the batteries bad. I was able to charge the rest although I confess I have no idea of a method to check how “good” these batteries are. What I don’t understand is why the laptop pack as a whole won’t hold charge but the individual batteries do? Does it mean that there are one or more bad batteries in the laptop pack? But since they all charge individually how could I know which ones are good/bad? By the way, if anybody needs any batteries I could mail them to you if you are willing to pay the shipping; or maybe send them to any moderators for giveaways? Thanks.

Did you notice a circuit board in the casing with the 18650s? That’s probably what failed. Most of the new-model dead packs I’ve found have had 100% good 18650s.

The pcb failing could be the issue in a couple of packs but I doubt that is the cause in all of them. It has to be one or more of the batteries but I don’t know much about battery chemistry. I read the post in the other forum that is mentioned in this thread and I think that when the poster says to throw away any battery that has a variation of 0.1 volts is too extreme. Does anybody else has a better insight on this?

I took a course in laptop battery refurbishing for the company I used to work for. The main issue why a laptop pack “goes bad”… the end of life switch. The manufacturer can set this to activate at a certain age, or after a specific cycle count. Also, if the battery pack senses a temperature over 68c (for most of the ones I worked on) it can also flick the “end of life” switch. Sometimes they have a thermal “fuse” too.

They are difficult to refurbish because as soon as you remove power from the battery pack circuit it wipes all the programming in it (and won’t charge when you put it in a laptop) :frowning:

-Jamie M.

THANK YOU for that insight!

… I agree! That

But I can’t see where anyone ever said that. Balancing cells is only an issue for multi-cell lights…

You throw them away recycle them when they won’t hold a charge anymore. When you pull one from the charger and it drops from 4.2v soon after (especially if it keeps dropping — that’s a hoot to watch), that’s one to recycle. If your torch goes dim too soon, adios to that cell too. If you’re feeding a multi-cell torch, match cells as best you can (0.1v is still extreme — you’re going to stop discharging them at ~3v anyway) and keep the sets together for life.

If our packs have dead cells, well, that explains why we got them for free. Otherwise, if all the cells test good, the protection circuit is all that’s left to blame — for our free cells.

Let me start out with a little background.

I quit smoking about 4 years ago and got into electronic cigarettes. When I moved up to the larger mods I needed 18650 cells. So, I started scavenger packs which got me into flashlights and mobile power banks for charging my phones and tablets off of.

I’ve busted a lot of packs and probably have 250+ 18650 cells here at the moment and given away another 150-200. I have about 2.5 shoe boxes full… And not little ones…the kind that hold size 12’s …so my count may be way off.

The numbers on the pack don’t give a lot of insight, you can grab 2 packs with the same WH and voltage etc and 1 could have Sanyo 2200mah cells and the other sony 2400mah cells.

I try to pick the smallest pack, so obviously the least amount of cells which is usually 6, with the highest WH rating.

As long as you stick with the name brand packs you will always get good UL listed cells. Stay away from the knockoff replacements from china.

I’ve got a few newer packs and they seem to be using Sanyo 2800’s as of lately. But generally you will harvest cells between 2200-2400mah and the occasional 2600mah. Newer packs may contain 2800’s.

Do not get the newer apple brand packs as they are no longer lithium ion cells. The older square ones that are about 3/4” thick will contain 6 cells.

You will normally get Sanyo/Samsung/Sony/Panasonic and LG’s, which are all great cells.

Here’s how I test them…

Be careful because stabbing yourself in the hand with a screwdriver and paper cut like slices from the very thin steel bands happens too. Wearing gloves is challenging so being very careful and taking my time is my method.

Once i bust them out I start disconnecting them in groups…usually groups of 2’s. Be very careful not to jump a pair of them. The tabs that are spot welded on the tops of the cells have weaker/smaller welds and come off the positive and negative terminals much easier than older cells. Either way I use a pair of needle nose pliers and get an edge up enough that I can get a grip on it…snug the side of the pliers over as close to the welds and grip on, then with a twist of my wrist roll the pliers. Usually they come off pretty clean. But, sometimes you will have some tiny sharp barbs that may need a little grinding. Try to keep the cells in the same pairs you took them out in.

Now it’s time to test voltages. I have the colors and marking pretty much memorized, you can decide if you would like to search what they are during whichever step you choose so you know what you have.

Usually the electronics in the packs go bad before the cells. Any group of cells that are lower voltage than the rest…and usually there will be a big difference, they get pitched.

Any cells showing signs of heat or corrosion get tossed. Usual cells will be above 3.0v anything down to 2.5v or so I try to bring back but it may not always happen. Below 2.5v I toss.

Now you can start charging the cells. Never leave the room for more than 10-15 minutes without checking the cells for excess heat. If the cells are just a tad bit warm that’s ok, but if they start getting hot they need pitched, due to the internal resistance and to reduce chances of having an issue down the road…it’s just not worth it.

DO NOT start charging cells and leave your house for an hour or 2 unless your insurance is paid up and you don’t mind living in a hotel or with your In-laws for awhile.

Once fully charged I check voltage make sure they are topped off…obviously any cell that took much longer than 2-3hours to charge to 4.2v is probably done for.

Over tenet month or cell I do checks on the cells… A few days after the charge I check voltages crossed all cells and not e them if it helps you. Then again at 1 week, 2 weeks and 1 month.

If they went from 4.20v to 4.18v in a month or so that’s within the normal range. But if you check them and a week late they are at 4.12 or 4.09 etc then you may want to consider putting them in a cool dark corner for emergencies or just get rid of them. That’s a person preference as you can decided what’s acceptable to you.

Manufacturers tell you that cells will degrade less over time if left at a half charge, which from what I have seen is usually around 3.5v or so. I haven’t found this to be true. I have cells I charged 2 years ago that still have a voltage around 4.12-4.18 and work just fine and if their capacity has diminished, it’s not noticeable to me over some fresh cells.

I leave all my cells charged fully should I need them.

If there’s any information I might bye able to share with any of you please feel free to let me know. I have browsed this forum for about the past 18 months off and on and after reading this topic I figured now is the time to make an account.

This really is a great resource for flashlight and battery related info.

Regards,

–30cal

Welcome to the neighborhood!