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Reclaimed Li-on cells .... surprising !

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slaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Topic: Reclaimed Li-on cells .... surprising !
    Posted: 20 January 2017 at 7:29pm
Well - time on my hands cos of no feckin work - which funnily enough, co-incides with no feckin money to spend on bits/stuff to tinker with ..... but ....

Went down the local market coupla Sundays ago as usual - they had a buch of laptop batteries from an office clearance. I explained to them it was highly likely that these packs were dead/nearly dead/no use for laptops - and walked away. Came back a while later and was offered the whole lot for a quid :-) - so .... go on then might get a few useable cells out of em.

These (original) HP packs - 3s2p like most - were a _bitch_ to get into - but much effing + blinding later I had a couple of 3s2p packs of 18650 cells accessible. Measured em and got 1 with about 9.something V across it .... OK hope for that one - and another sitting at 5.something V ..... gotta be a basket case I thought - close to chucking it out - as conventional wisdom has it that when cells get below about 2.5V they're done for.

Charged up the 9.xx V one and it seemed to accept a decent amout of charge .... cool.
Then thought - well out of curiosity lets just see how the low voltage one behaves. Told the Turnigy Accucell 6 charger it was a 2S (as it just erros out when cells are below 2.5V) .... very quickly the charge voltage goes up to 7-8-9V ..... so I disconnect and tell the charger its actually a 3S ..... and now its happy to charge away. Seemed to accept a very decent amount of charge .... <whoa - is this too good to be true ?!> ..... well yes - kind of. But ...

Jist of it is - that the cells seem to be able to accept a high proportion of the original capacity - but on discharge the voltages sags much more than a pack of "good" cells - classic case of elevated internal impedance. Discharging at a (constant) current of 500mA drops the voltage by nearly 1V.

So lets try it powering a TA2020 amplifier .... well it damn well WORKS - fine. So lets leave the multimeter across the pack while playing music at "close to clip" kind of level. Certainly the voltage is dropping quite a bit on peaks, as the meter seems to be fast enough to show that - not with any kind of precision - but its definitely dropping by a volt or more - but it also recovers pretty quickly.

So - thinking is - 500mA = bit over 5W at 11V or so - shuld be roughly equivalent to a 2x 10W amp up to clip (on class D chip-amp) - and this seems to be borne out by my crude testing. I'm guessing the 3300uF reservoir cap on the Lepai 2020 amp is delivering the current on peaks quite well.
I feel an upgrade reservoir cap mod coming on :-)

A-a-any way .... I've the "dead" laptop pack powering the amp playing music at close to full welly for a good couple of hours - and there's still a fair bit left in it !! Chuffed !!

So there ya go :-) I feel a "build a boombox for a tenner" project coming on :-)
Skip-dive for a pair of speakers from an Argos £29.99 stack system, sub-fiver chip-amp module, "dead" laptop battery, coupla little odd's'sods .... bingo :- (Well actually that doesn't include a Lithium charger, but owning one of those should be compulsory for boombox builders :-) )

So - anyone here been barking up this tree ? Any experiences ?



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amlu View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amlu Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2017 at 2:52pm
i got myself a proper RC charger, with controlled discharge and capacity meter function.
managed to scrap plenty of batteries over time, got bit of experiences.

-when found dead (less than 2.5v per 18650) they will be of no use
-most will accept charge and fully charge  but capacity will be crap...

i charge all unknown cells to 4.1V, then run discharge on them, drawing 1A, down to 3.2V (this value can be lower but kills the battery sooner)  and measuring mAh
some dead ones will charge ok to 4.1V  but measured capacity is under 100mAh
one laptop pack come up as 6 cells, each can do around 1200 mAh
my new chinese 18650 headtorch come with 2 new extra cheapo cells, measured them as around 350mAh

bought myself a pair of those to compare results, found that cell on some forums for vape smokers :

PANASONIC NCR18650B

http://www.ebay.co.uk/itm/111860580419

and on the same test they measured 2300mAh each.


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slaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2017 at 4:38pm
Originally posted by amlu amlu wrote:



-when found dead (less than 2.5v per 18650) they will be of no use
-most will accept charge and fully charge  but capacity will be crap...



Well what you're saying was waht I always believed - but my little experiment proved otherwise I think - thats the reason for my post really.

I say whats happening with "dead" dells is not actually losing capacity, but the internal resistance rising a good deal. This makes them useless for powering a laptop, but they can still deliver small current OK (like 0.5A from a 2P array, as above). Even then, the voltage will sag - but a 12V chip amp seems not to be bothered about that.

All the cells I have are from original HP/Dell/Lenovo packs - so the cells will be pukka Samsung/LG/Panny - unlike most of the 3rd party "replacement" batteries. Plenty of stories about dodgy 18650 cells from ebay etc having fraction of stated capacity.

Originally posted by amlu amlu wrote:


PANASONIC NCR18650B

http://www.ebay.co.uk/itm/111860580419

and on the same test they measured 2300mAh each.


Sure - well those will be pukka cells - unlike alot of the cells you can get for e.g. 25 quid for 20 from the bay
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2017 at 2:36pm
Hmmm, I have the old pack from my Macbook part disassembled, still on the shelf - being Apple, of course they don't use 18650's but rather flat pouch cells. Marked capacity is 11000mAH, for the 16.8 nominal voltage it must be 4s2p so they are probably "supposed" to be 5500mAh per cell. You were reading about 100mah for what ought to have been maybe 800? So about 12% left....it could still be nearly a 1500mah pack. Good maybe for powering a music source and radio transmitter! Not much more than 150mA draw there. 
The way Apple work it is to have the machine shut down and absolutely refuse to reboot, even with the charger plugged in, if the battery chip reports under a certain capacity - so I'm fairly certain the pack was never over-discharged in its working lifetime.
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slaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 09 February 2017 at 12:38pm
Well - quite an interesting little extension to my "experimenting" with this ....

Using the "saggy" reclaimed cells to power a Lepai 2020 amp has seemed to work OK, despite the fairly large voltage drops. I ran one for about 3-4 hours playing music (admittedly at a notch or two lower level than I normally would) and the battery could have played longer. Now the Lepai fas a 3300uF smoothing cap (leastways its marked that way :-) ) - so maybe thats helping counteract the voltage sag. Some of the very cheap 2020/similar chip-amp modules have rather less reservoir methinks - might behave differently.

Anyway - following a rummage in the bits box - discovered a little cheapo DC-DC board I've had for a while - one of these :- (except I got mine for about £3 direct from China :-) )

http://www.ebay.co.uk/itm/DC-DC-100W-3-35V-12V-to-3-5-35V-Boost-Step-up-Module-Power-Supply-Voltmeter-HOT/331863659902?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D20140122125356%26meid%3Dbfae23d4ad264ab08b04f0cd98bddf6a%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D321964888830

.... and put it between saggy battery pack and Lepai amp. Now this nifty little dc-dc board lets you toggle the voltmeter between i/p and o/p - and .... well the dc-dc board seems to be able to regulate the supply quite effectively .... I had o/p set to 13.5V - and checking a saggy battery... well it was sagging really quite a bit - 11.5V or so on o/c, but dropping well below 10V - and down to below 9V at times on peaks, but staying at 13.5V consistently according to the built-in meter,
Now I don't know how fast this meter is - probably not particularly responsive to peaks/troughs, but enough to give you a good idea.

I've yet to check how this affects the run-time, but .... well its kinda interesting. Not sure how useful :-)



Edited by slaz - 09 February 2017 at 12:41pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SamV Quote  Post ReplyReply Direct Link To This Post Posted: 16 February 2017 at 3:42am
Nice find :) If you want a bunch of 18650s that I no longer use for vape stuff you're welcome to them. There's only like 8 or so and most are Sony VTC4s/Samsung 25Rs or the Panasonics NCR-B. The latter of which actually powers Tesla's cars.
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