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

I like going for recent Lenovo cells. (used to be IBM)

They have only been marked Lenovo only for about 5 years, and all 5 of the packs i’ve opened had Sanyo 2600UR cells.

Can you post or PM me a model number for the battery pack itsself?

I want to test my formula to see if it's close.

Also, I think I'm going to go for lenovo or sonys aswell, seem to be alot of them cheaper than dells.

Specifically the pack I opened was for the T400.

The part number for that is: 43R2499

It was a 9 cell battery.

Sometimes you get lucky and the sticker on the battery pack will tell you what brand of batteries it has inside.

Here are the tell-tale signs.

Zoom in on the picture to see what I’m talking about.

http://www.summit4laptops.com/files/items/HP%20Laptop%20Battery%206120-20120807-160629.jpg

Where is it made? CELL ORIGIN KOREA FURTHER PROCESSED IN CHINA

Battery is from Korea. Hmm… the only lithium battery I know to come out of Korea is LG.

There’s also a code which I’m guessing is the code for the battery. “SDI-CHA-LG

Opened it up…Yup, it has LG cells inside.

Search ebay for 'HP 9600mAh', you'll find new aftermarket replacement packs with 12 2400mAh no-name but solid cells inside, for around $30. They're not spectacular, but they are all new, and you won't have to throw half of them away like you will with a clapped-out abused used pack.

We've found Toshiba 6-cell packs with grey Panasonic 2900s, and Acer packs with the nice purple 4.30v 2800mAh Samsung ICR 28As inside. New or new old stock packs are almost always better value for money, breaking open used packs really only makes sense if they're free or nearly free. Don't spend real money on used packs, you might get a few good ones but you'll also end up with a lot of stuff that has to go in the recycle bin.

Just used my formula on that pack
Capacity: 7.8Ah / 7800mAh
Cell: 9 Cells
Paraelle: 3 rows of 3(Guessing)

[(7800*9)/3]/9=2600mAh per cell.

I used your way to figure out the same answer:
48Wh/10.8V=7.778Ah=7778mAh
10.8V/3.7V=2.92 so round up to 3 paraelle.
9/3=3
So, 7778/3=2592. Up to 2600mAh per cell.

So buy Cells made in Korea for LG and chance every other sell if they are from china?

I guess what I'm trying to say is that sometimes you'll get lucky and the label on the battery will tell you if it's an LG, Samsung, or Sony battery inside. Tongue Out

Thank you everyone for your replies.

Yeah, on that one I was doing it for FMcamaroZ28's pack, since we knew what the final value of each cell should have been.
Just wanted to see if my math worked correctly for each cell.
Thank you for the help calculating gauss.

I knew what you meant, I will definitely look for markings like that. Thanks for that tip.

Would a higher capacity battery, like an 85Wh, or 5200mAh mean higher capacity 18650s inside? (I even saw one that was like 104Wh.)

Probably, but not necessarily. It depends how many cells there are. I've only seen one 14.4V battery (4s), all the rest say 10.8 or 11.1V, which is 3s. Take the number of cells/3, or 4 for a 14.4V pack, and that's the 'p' number, the number of cells in parallel. divide the mAH rating of the battery by the 'p' number to get the individual cell's mAH rating.

I’m using two of these in my two laptops. I usually run them plugged into the mains and charging they are about 4 years old now. Do you think that they’d be worth stripping down when they eventually fail? I’ve still got the two original 6 cell packs with only about 3 weeks use on them then charged and stored, any good do you reckon. The new packs are £57 ~ $90 so I’m going to use these until they fail.
I’d like to think that I have a few cells for any emergency situation that might occur.

If you really want to dive into the deep end of the pool, you could start here: How to calculate battery run-time

Dim

+1

Only gas money.

If someone tries to sell you a dead battery pack, feel free to, as the saying goes “use whatever language you deem appropriate” and stop going there.

OT, with apologies.

I believe, and cannot prove, that what you are doing will extend the life of your packs and cells.

I have an Inspiron with 2 packs, and I always left one in the bag, one in the PC on the wire. I’d swap them when onsite and one ran down. I considered one as a “favorite”, but tried to keep them both topped off. I didn’t think about it until it was too late, but one of them died a lot sooner than the other.

If you could stand to kill one, maybe you could pick one to stay on the wire and the other to get deeply discharged and recharged as needed… That might answer some of the “dead pack” questions…

Just sayin…

PS: the individual cells should be in the 2200mAh range, which means they’re not all that exciting, but they’d certainly make lots of light for you.

Was in town earlier and stopped in at a PC repair place, he is going to see if he has any dead laptop batteries - but they might have just been chucked out. Going back tomorrow.

Got two chances I guess!

Got lucky today, clients laptop was stolen and he had a habit if using his laptop without battery installed, I ended up with 6 Sanyo cells that are 4V pulled , busy charging now before I do capacity tests.

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?