Capacity loss

Geek

Geek

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Joined
Aug 15, 2017
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920
I have tested 100 or more cells. I do two capacity checks. Some of my cells have dropped from 2000mah to less than 1000mah. Its odd, using an opus to test
 
Going from 2Ah to 1Ah seems just odd. How many of the cells?

Same type of test?
 
daromer said:
Going from 2Ah to 1Ah seems just odd. How many of the cells?

Same type of test?
Click to expand...

That it is Samsung ICR18650-22F. Charge and discarge at 500ma. Would not have second tested side I re wrapped them for flashlight batteries. Same opus. Same test. My mind is baffled.

About 5 so far tested
 
So 5 out of 100 cells have on 2nd test gone from 2Ah to 1Ah?
Were they used in between? Different temperature when testing?

I dont see how its possible. Opus brooken?
 
daromer said:
So 5 out of 100 cells have on 2nd test gone from 2Ah to 1Ah?
Were they used in between? Different temperature when testing?

I dont see how its possible. Opus brooken?
Click to expand...

No these cells were not used. All the others still show just fine. Just these 5 cells. All from the same laptop battery. I will allow them to rest and check for self discharge. The 6th one tests just fine ~2ah. I didn't get them very hot when they were re-wrapped, used a hair drier, and held them in my bare hands. It was about 10c cooler than the day I originally tested them.

Never seen anything like it.
 
10c diff in ambient can do alot but half the capacity. sounds like bad cells. Should show or I hope it shows on selfdischarge test.
 
Geek said:
Never seen anything like it.
Click to expand...

I have.

I also thought I was going crazy ... so ignored it, and continued harvesting. But something kept bugging me in the back of my mind ... I knew what I saw was real. It happened more than once for me too. Not a whole lot (only found it with a few cells). But then again ... I've not been testing twice / looking / testing for this.

When I first started harvesting cells from laptop batteries I would sometimes forget the capacity between taking it out of my Opus and marking the cell. Y'all know how it is ... cell covered with sticky stuff right where you wanna write on it ... peel that gunk off, and *poof* number vanishes from brain... so I'd put them back in the queue for precharging and testing (again).

When I saw this thread I changed from lurker to poster... I think this is perhaps a significant problem for smaller packs ... and potentially needs further investigation. I'm very interested in any insights into this 'phenomenon'.

Surely we can't be the only two who have bumped into this? Although ... harvest --> test (once) --> repack ... doesn't really allow for this to be discovered.


Anyone else?
 
sil5er said:
Geek said:
Never seen anything like it.
Click to expand...

I have.

I also thought I was going crazy ... so ignored it, and continued harvesting. But something kept bugging me in the back of my mind ... I knew what I saw was real. It happened more than once for me too. Not a whole lot (only found it with a few cells). But then again ... I've not been testing twice / looking / testing for this.

When I first started harvesting cells from laptop batteries I would sometimes forget the capacity between taking it out of my Opus and marking the cell. Y'all know how it is ... cell covered with sticky stuff right where you wanna write on it ... peel that gunk off, and *poof* number vanishes from brain... so I'd put them back in the queue for precharging and testing (again).

When I saw this thread I changed from lurker to poster... I think this is perhaps a significant problem for smaller packs ... and potentially needs further investigation. I'm very interested in any insights into this 'phenomenon'.

Surely we can't be the only two who have bumped into this? Although ... harvest --> test (once) --> repack ... doesn't really allow for this to be discovered.


Anyone else?
Click to expand...

Good,so I definitely wasn't going nuts. I have had a lot of luck with these Samsung cells (ICR18650-22F). Most of them have held close to their original 2200mah. I haven't had any others do this.

I have indeed kept these batteries for use in torches ect. Next time I charge them I will use the Opus and test them again, just for curiosity's sake.

Sil5er, did you take note of the make and modal of the cells that have done this? Would be interesting to know.
 
Geek said:
Good,so I definitely wasn't going nuts.

[...]

Sil5er, did you take note of the make and modal of the cells that have done this? Would be interesting to know.
Click to expand...

Nope, you're definitely going nuts -- and neither am I ! *phew*.

But at the time ... I did not linger, this includes taking any notes, so alas no ... I don't recall which make or model. Or even if they were the same (as each other). I do definitely recall it happening more than once though.

I wonder if this correlates at all to cells which won't sit at 4.20v ? I'm not talking about self dischargers ... they go straight in the fail pile. Recently I have been paying much more attention to cells which wanna top out at 4.179v etc. I used to ignore this, as I figured I would never again be cycling them up to that level, but lately I have been wondering if this is a sign of impending doom for the cell. I would definitely buy any machine that did COMPREHENSIVE testing in an automated fashion ... maybe like the Batlab, if it ever becomes available for public sale, with working software etc...
 
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