>>>>> I just tested a couple of cells that were last charged around 3 months ago
What was the voltage after 3 months?
If a cell drops back to 4.10 after a couple of weeks of nonuse (assuming it started at 4.20 volts), it just lost 20% of its capacity for me. And 20% of its BRIGHTEST capacity.
The way I look at it, I can really see a difference in light output when the battery reaches 3.7 volts or so in unprotected cells (from a 4.2-volt starting charge).
If I have a cell that drops to like 4.10 or less after a couple weeks or even a month, I chuck it. I have WAY too many other cells (WAY too many) that hold 4.2 volts for months.
In no way shape or form, am I suggesting that others do this. Nor am I criticizing others who keep cells that drop from 4.2-4.10 after a month. I just have so many batteries (pushing a ridiculous 300 I think at this point) that I need to somehow winnow the best from the less.
That seller has a really good track record and is in the US too. I think it’s time for me to recycle all my poor performing used laptop pulls (most of them) and use the remaining used pulls in cars during the summer months.
>>>>>Are you saying the couple cells you tested had dropped to 4.10?
No, no ,no …. I’m just saying in general. That’s one of my main ways of judging whether to keep a battery or chuck it. I haven’t had these long enough to see how they’ll do. Talking more about pack pulls. These 2900s are new (supposedly) and should be fine.
A couple did drop to 4.16 over the first couple days, but that was on the first charge.
Except for protected cells to use in my very few multi-cell lights, I use almost exclusively pack pulls. Although since I am a battery nut (hoarder might be a better description), I do buy a few of the more interesting cells to see how they do.
But I didn’t have enough batteries that were exactly positively the same to judge light intensity between lights simultaneously. So I got three of the 2900-mah packs for that end, but that’s really unusual. I find so many GREAT batteries in used packs, it kills me to pay for ’em.
There is this home depot in a town close to Death valley, and it’s like people buy NEW computer packs and throw them in the recycling bin there. It’s like Christmas every two weeks when I go there to town to do my food shopping (180 miles round trip). The guys at that home depot are so totally nice that they open up the recycle bin so I can look better. Last time I had three guys helping me dig through the mountain of dead duracells to find the good stuff. Best home depot i ever went to.
I opened up another pack and had 4 cells at 1.91 and 2 at 1.72. I checked again in the morning and the 2 1.72 bounced up to 1.84. I probably won’t get around to charging them till this weekend.
Mine came in. Cells are all marked 9511 (same batch reported in others). All were 1.78-1.80 Volts on arrival. Charged all at .5C to 4.2v to start them off easily. Ran one on the CBA this evening and discharging at 2A gave a total capacity of 2917 mAh. I’ll run a few more on the CBA after a few cycles but they look to be perfectly good cells on first test.
Thank you for reporting wiljen. I don’t have discharge testing equipment. So that information is appreciated. My cells have been taking the correct amount of time to charge about 3 amps and have been taking and holding full charges.
Interesting. So is the mAh derived from the single battery mAh multiplied by how many are in series, or by how many banks are formed? 9 cells, but divided into 3 per bank means 7200/3=2400. It would seem to work the same way for voltage… as 3.7v x 3 = 11.1v.
I’ve seen some Asus Eee PC cells showing 7.2v or 7.4v and 5800mAh. That means it has to be two banks of batteries in series, but the casing looks very fat like there are 3 rows of cells. Maybe there are 8 cells total, divided into 2 banks of 4 cells?
Correct. Cell capacity (mah) is multiples by the number of parallel banks. Voltage is cell nominal voltage times number of cells in series. The the second battery you mentioned is most likely 2s2p (3.7v*2=7.4v, 2900mah*2=5800mah). Maybe it looked fat because the cells are arranged sideways?
got 2 Acer battery packs… they all 2900 CGR panys (?) all of them 1.90V, try to charge them on Nitecore smartcharger… but after few seconds the lights stay ON… it won’t charge