DIscharging a battery into a 2 ohm resistor down to 3.0V gives 2700 mAh (starts a 2A, tapers down to 1.5 amps). These cells are spec’d to discharge to 2.5V and should give the full 2900 mAh if you took them down to 2.5V
I was getting 2700 mAh out of them even with the 10A pulses…
That is pretty good, right :)?
In China these are 9000 mAh cells…
“Lost in Translation” :)?
Here is the data sheet for these cells: http://industrial.panasonic.com/www-data/pdf2/ACA4000/ACA4000CE240.pdf
They show a 5.5 amp discharge curve. It also shows they should do 2700 mAh at 2.75 amp discharge to 3.0V.
Finally got time to test one of these. I charged the battery at .8 amps until fully charged, then discharged at 3 amps. Then ran another cycle. On the second cycle I got 2740mah at a 3 amp discharge rate down to 2.7v. Ran logview with the accucel-8150 to give me this graph on the second cycle.
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If anyone knows how to get the capacity on the bottom of the graph instead of the time, please let me know. I have spent hours trying to find out how to do that without any luck. :~
One of the 18 cells that I pulled from these packs has quite a bit more voltage drop after charging than the others. Most drop from 4.20 volts off the charger to around 4.18V after a few days. The outlier dropped to 4.12V It does measure OK capacity on the discharge tests. I’m gonna let it set for a couple of weeks and see what it looks like.
I had a bunch (like, all of them) that were dropping to 4.10-4.12v after resting overnight, after coming off the charger at dead nuts 4.20v. I'd been doing them 4 at a time in parallel, at 4A. Once I went back and topped them up individually at .5A rate, 4 days later they are every single one holding at 4.17-4.19v and staying there.
If these cells are headed to storage, the voltage should be reduced to about 3.75 volts before storing them, and keeping them in the fridge is a good idea as well, so they they do not lose capacity from sitting around fully charged.
Time and heat are enemies for li-on cells, but not charging to max voltage during use cycles will dramatically increase the life time of the cells, as well as not discharging to minimum levels.
The life span increases 3 times just from charging to 4.10 instead of 4.2, if I recall that correctly, and damage to the cells from voltage is eliminated at 3.92 peak volts.
You do lose a little run time, but don’t kill the cells off as fast.
Hi,
Some hobby chargers, like the one I use, an Accucel 6, actually has a function to charge a battery for “storage charge”.
Little update: This is the cell that I tested in post #152. I charged it up as soon as the test was done and has been setting ever since (A week ago). I have one cell resting at 4.18v (could be that I charged it a day or two later) but the rest measure around 4.17v.
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What batteries are in the Fujitsu E8110 battery pack? It is 6 cells and 5200 mah and it says 10.8 volts
Should be 2600mah, 6 of them haven’t the clue as to brand maybe sanyo.
I am wonder how calculate the capacity of some laptop batteries with 5200mAh, 7800mAh.
Need to know the voltage and number of cells to be certain. Should be 2600mAh cells though.
As an example, if the laptop battery pack has a capacity of 5200mAh, and has 14.4V output (3.6V x 4, series, 2-banks) and the 5200mAh capacity comes from the 5200/2=2600mAh cells. So most probably it is a 4S, 2P connected, 8-cell (2600mAh) battery pack.
It is so awesome that buy laptop battery to get 18650 batteries.
laptop pulls /can/ be a good way to get cheap cells if you are vigilent and careful. wouldn’t use them in anything but projects, or my cheapie $11 xml zoomie though, as the last thing I need is a unsound battery wrecking one of my ‘good’ lights.
charge to 4.21v, then discharge to 2.9v, and repeat 3-5 x. if the results are fairly uniform you got ‘new’ cells that were stored a long time.
In the long term not much difference at all… the cells will eventually all wind up in the landfill/recycle center someday. Also if the packs are sent to a recycle center intact, the housing will probably be recycled. I bet 90% of the people that salvage laptop cells put the housings in the trash.
The truest sense of the word recycle should be to use what still has useful life instead of tossing it into a land fill . It actually is good for the environment as something else doesn't need to be produced and landfilled until the full use of these cells is over . the premature tossing of battery packs is the reason laptop pulls have any viability for us as flashlight enthusists.
When some assistant manager at a home depot refuses to let you dig around in the recycling bin use this logic against him .
The truest sense of the word recycle should be to re-use.. not toss .
In the immortal words of Monty Python ..>
I'm not dead yet ..