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Hi Everyone
#11
Within certain limits it has to be expected that the results are inconsistent, especially with these cheap testers. If the differences aren't too big then it's not a big deal.
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#12
(03-10-2019, 04:12 AM)Oz18650 Wrote: Another update.

So far I have extracted over 550 cells and I am hoping that the majority of the cells will be good.  
Only a very small number have had low voltage.  The vast majority are between 3.6 and 4 volts.
I have not sorted out what my test process will be yet.  
I have a few hw586 (similar to zb2l3) testers, but over the last few days I have done some repeated testing of 1 cell, with the same charger and capacity tester and the results seem a bit inconsistent.

yahoo!  you have a source (of cells) -- that is fantastic news.  took me months to find, too.

I don't worry about low initial voltages.  Other than having to pre-charge them VERY slowly (and I mean very slowly ~10-20mA) ... I find most test out well, capacity wise (I dont care about, or test for IR).

My test process involves (in brief) a super slow pre-charge (as needed), wait for a week (ish) to check for selfdischarge, then I triple test each cell (pair..) for capacity, then level them all to a storage charge of ~3.92V.  When I need to build, I select some roughly matching cells, check them again for self discharge, re-level to 3.92V, and get busy with soldering iron.

I test with 'cheap' testers (Opus BT-3100 v2.2) and they can be a bit off, as DarkRaven noted, BUT ...

Most cells test out all three times with exactly the same capacity results.  IE within 0.5% (!).  And some cells test less each time ... circling downwards rapidly -- this is partly why I triple test -- so I 'discard' them no matter what their capacity.  And yet some others rise each test (just a little, not much) ... and a very few test out like a regular yo-yo, IE all over the place.  I dont much like those either.  Im not entirely sure what makes them do this, but ... this is my experience.  The main thing for me is that my testers are all calibrated the same as each other, and therefore it doesnt matter which tester I use, so the capacity results are similar between them.  Best of luck developing your own style/methodology.  I do not believe there is any one 'perfect' method, its a very personal choice etc.

I would be interested in whether you have similar results with a larger sample than one cell.  IE is it your tester/s, OR is it that particular cell?
--    ----    ----    ----    ----    ----    ----    ----    ----    ----    --
all systems nominal... rock on.
-----------------------------------------------------------------------
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#13
(03-11-2019, 08:27 AM)DCkiwi Wrote: I don't worry about low initial voltages.  Other than having to pre-charge them VERY slowly (and I mean very slowly ~10-20mA) ... I find most test out well, capacity wise (I dont care about, or test for IR).
DCkiwi,

I don't worry about low voltage either and do a slow charge as you. But the IR thing well I guess everyone is entitled to their opinion.
I personally feel that it is important to the degree that I can determine the health of a battery with a simple IR test. I mean the manufacturer has given us in their spec sheets (not all of them) their recommended IR state of the battery at 1kH AC. To me when a manufacturer recommends a measurement  to be taken and gives a specific value within certain tolerances it means something to me. Kinda like torquing the head bolts on an engine. You don't just make them tight because tight can mean a lot of different things to different people hence there is a "standard" be it Nm or ft-lb. So I kinda think IR has a place in this mysterious world of 18650 and Li ion and the manufacturer has given us a standard "1kH AC 4 wire Kelvin".

Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 6/10/2019
Total Number of Cells                          5940
Cells  >80% of Capacity                      4334
Cells <80% of Capacity                       1605
Cells ≥2200mAh & ≥ 80% & ≤75mΩ    2800 +236
For Info Google Drive
Not your average Wolf       
            Cool



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#14
(03-11-2019, 12:04 PM)Wolf Wrote: [...]
the IR thing well I guess everyone is entitled to their opinion.
I personally feel that it is important to the degree that I can determine the health of a battery with a simple IR test. I mean the manufacturer has given us in their spec sheets (not all of them) their recommended IR state of the battery at 1kH AC. To me when a manufacturer recommends a measurement  to be taken and gives a specific value within certain tolerances it means something to me. Kinda like torquing the head bolts on an engine. You don't just make them tight because tight can mean a lot of different things to different people hence there is a "standard" be it Nm or ft-lb. So I kinda think IR has a place in this mysterious world of 18650 and Li ion and the manufacturer has given us a standard "1kH AC 4 wire Kelvin".

I *do* think IR is important, in terms of what you said (above).  BUT there is ZERO importance to ME, so I dont pay attention (irrelevent) or test for it (waste of my time).  Heres why: 1/ many (most?) of my cells are used in big batteries with LOW discharge setups -- think C100  (IE <20mA)  2/ the used laptop cells I process here in NZ are almost ALL high IR. 3/ my motivation is to actually USE these recovered cells, thrashing them to death, NOT to just immediately return them to the landfill from which they were rescued. 4/ I am a cartridge style fanbois.  this makes swapping out dead cells much less stressful than if they were all buried in 80s packs etc.  5/ IR is 'tested' implicitly by the triple capacity test.  if they survive that ok, then their IR is ok for me.

When I need super low IR (EG 4WD electric skateboard), I use cells from powertools.  If I needed reliable cells I would not choose recovered cells, I would buy the latest chemistry, brand NEW.  and how does the saying go? ... 'the best [cell] is the one that youve got' ...

apols for any confusion here.  wasnt wanting to start another IR discussion, more made the comment in passing, and in relation to previous post of inconsistent capacity test results.

EDIT: @Oz18650: If you back off the discharge/test current, do the capacity test results become more consistent?  If so, this would indicate to me that you have an IR issue (almost dead) ... if not, then I say they might be End Of Life (dead) ...
--    ----    ----    ----    ----    ----    ----    ----    ----    ----    --
all systems nominal... rock on.
-----------------------------------------------------------------------
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#15
Thanks to each of the contributors on this thread!
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#16
(03-11-2019, 08:00 PM)DCkiwi Wrote: EDIT: @Oz18650: If you back off the discharge/test current, do the capacity test results become more consistent?  If so, this would indicate to me that you have an IR issue (almost dead) ... if not, then I say they might be End Of Life (dead) ...

The test I did was with only 1 of the 2 supplied resistors as I was wanting the test to be "easy" on the cell and hoping it would be more consistent that way with a smaller voltage drop due to the load.

I have purchased some zb206 testers, which should do IR testing however I have not seem much about how accurate these are for IR. 
I have also purchased a yr1030 IR tester, as recommended by another very helpful member here.

I have extracted over 1000 cells now, so I am really keen for the test equipment to arrive, so I can start on testing.

I think I have a good grasp of the pack design part of this project, but need to find out more about other parts of system design.
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#17
(03-26-2019, 10:31 PM)Oz18650 Wrote: [...]

I have extracted over 1000 cells now, so I am really keen for the test equipment to arrive, so I can start on testing.

I think I have a good grasp of the pack design part of this project, but need to find out more about other parts of system design.

Nice update ... : )

While you are waiting for the test equip to arrive, may I suggest something to take all your time until then?

pre/charge all your cells ... let them sit for a week (or two, no longer) at 4.20V (assuming you using LiIon-Co chemistry).  then test for selfdischarge. 

I generally find that any that go below 4.10V are junk, and I am suspicious of any that drop below 4.16V in this relatively brief time.  this can be a mind numbing task, but takes some time, depending on your charging/lab setup.  you might be able to weed out 50+ cells that self discharge, and use slots in testers for viable cells only.

then you could even start on 'flattening' these failed cells, ready for final disposal ... all before testing equip arrives.  fun fun!
--    ----    ----    ----    ----    ----    ----    ----    ----    ----    --
all systems nominal... rock on.
-----------------------------------------------------------------------
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#18
Thanks DCkiwi.
The ZB206s arrived yesterday! However i am still waiting on the yr1030 for IR testing
I have started some testing of thr zb206s to verify that I am happy with using them.
First cycle with a cell looked reasonable. Now to see how repeatable testing is.
I also have an idea for testing the tester which might be good to verify accuracy. I will try it out and report back here.
The steps you suggest before testing starts could be good, however I want to measure and record voltage and IR of the cells before charging and testing, so I will wait for the IR tester to arrive for testing to really get underway.
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#19
Welcome James!
Oz18650 likes this post
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#20
Thanks 0yx26.

I have extracted over 1300 cells now.

Still have a several hundred to go, before getting more cells.

I am thinking of aiming for roughly 14s 100p for about 10kwh, so depending on how my testing goes, I might get close to that.

I am hoping to get some zb206s set up with power and cell holders this weekend.

I might have to start a build thread.
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