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"Generic" Cells - Are they any good?
#11
(01-31-2019, 01:02 PM)Overmind Wrote: I agree with Dallski here, these home testers are good enough for general use but not good enough for professional use.

If I cannot set the exact discharge max current and the minimum voltage specified by the manufacturer, the test is not professionally relevant. Also, none of the testers I have encountered support high discharge currents. That makes most of the tests of high power cells irrelevant. They will test fine at 1A discharge and instant die at 10 or 20A.

FYI
Icharger x6 supports 30A discharge, flexible settings and so do a lot of other "Professional" units.
The question is if you are testing hundreds if not thousands of individual cells all you are trying to get is an idea of capacity.
That is a little difficult testing 1 Cell at a time with a "Professional charger/tester".
Additionally most of us that are building powerwalls are looking at a max of 1A discharge rate and that only happens during peak startup of some devices.
Most of the time the "idle" discharge is going to be around 250mA to 500mA ovoiously depending on the p size of the pack.
I just purchased a SkyRC M3000 and will see how that works but at $110.00 its out of the price range of some to purchase many of them even if you get a volume discount. Some are struggling to get 1 or 2 charger/testers.

Wolf
Korishan likes this post
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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#12
I've done 23 full cycles now, nothing interesting to report yet. Cells are having a max deviation of about 2.5% between highest and lowest test so far. If anything, I'm genuinely surprised how consistent the Opus is! I was expecting much larger swings!

I was thinking of modifying the test just slightly. Using an infrared thermometer (cheap chinese gun-looking thing), I've noticed that cell temperatures during discharge are highest on the right 2 cells. Going left to right, they are usually 35*C, 38*C, 41*C, 40*C in a room with an ambient temperature of 23*C. During charge, they are all around 33*C. I believe this has to do with the Opus design itself and substandard fan. Starting with cycle 26, I was going to shift the cells 1 slot over (and then again at cycle 51 and 76) to avoid any heat-related bias. So in cycles 26-50, it would be LG, CJ, ASO, THLD; cycles 51-75, it would be THLD, LG, CJ, ASO; and cycles 76-100, it would be ASO, THLD, LG, CJ. I think that would be better than adding an external fan. Any thoughts?
Formerly known as Dallski
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#13
(02-07-2019, 05:47 PM)Dallski Wrote: I've done 23 full cycles now, nothing interesting to report yet. Cells are having a max deviation of about 2.5% between highest and lowest test so far. If anything, I'm genuinely surprised how consistent the Opus is! I was expecting much larger swings!

I was thinking of modifying the test just slightly. Using an infrared thermometer (cheap chinese gun-looking thing), I've noticed that cell temperatures during discharge are highest on the right 2 cells. Going left to right, they are usually 35*C, 38*C, 41*C, 40*C in a room with an ambient temperature of 23*C. During charge, they are all around 33*C. I believe this has to do with the Opus design itself and substandard fan. Starting with cycle 26, I was going to shift the cells 1 slot over (and then again at cycle 51 and 76) to avoid any heat-related bias. So in cycles 26-50, it would be LG, CJ, ASO, THLD; cycles 51-75, it would be THLD, LG, CJ, ASO; and cycles 76-100, it would be ASO, THLD, LG, CJ. I think that would be better than adding an external fan. Any thoughts?

Dallski,
Any thoughts? Any thoughts? Of course you know how to get my thoughts just put any thoughts at the end of your post. Tongue 

The Opus for all of its flaws is a pretty good tester and the biggest swing I saw in my tests was (as you experienced) 3% not bad I would say.
 
The design flaw of the Opus is the fan placement it draws air from left to right so it picks up the warm air and just multiplies it across the cells.
A better design would have been a central fan either in the bottom of the Opus or at minimum in the middle at the top. Maybe a tad bigger wouldn't have hurt it either. Shifting the cells sounds like a reasonable idea as to see if temp of the cells screw the results a little but I wouldn't be surprised that they would be pretty close as these cells are tested at these temps anyway. One thing to note though is that the spec sheets will always tell you what the standard charge and discharge current should be along with the cutoff V.
Example:


So this particular "generic" cell likes to be charged at 0.5C and discharged at 0.2C to 3.0V
Not exactly within the Opus parameters but close as far as charging is concerned.. So if you are discharging at 0.5C you are exceeding the "Standard Discharge" by 570mA and I would suspect there would be some temperature involved.

Finding the spec sheet on "Generic Cells" may be a challenge but that being said "most" (and I say that with knowing there are many exceptions to the rule) cells "Standard" charge is at 0.5C and discharge at 0.2C.

Those are my thoughts.

Wolf
Dam I didn't mention IR anywhere.
Oh yes I did.
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
I would start by putting a desk fan in front of the charger, before moving the batteries around the slots. A few runs with the fan in place will show you changes that are occurring only because of the temp change.
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#15
Shawndoe, that was my first choice, I might try that for run #26 tomorrow.

Wolf, your thoughts are always welcome and appreciated, as long as you dont mention internal resistance...j/k.

But on a serious note, even though the temperature is not extreme, it can make a big difference in the number of cycles a battery can get (I'm thinking Nissan leaf air-cooling vs Tesla liquid cooling) I just dont want someone to discredit my results on the fact that the genuine LG battery was subject to the highest temperatures. Also, I don't believe any of these cells have a data sheet, which is part of the reason I'm collecting this data. Unlike a lot of "data," I see from people selling stuff (batteryhookup, for example), I am in no way selling anyone anything. This is mostly for me, and I'm trying to share with the community because there seems to be a lot of fear and negativity toward generic cells, and I want to see if that is unfounded. I'm going to be building a powerwall out of approximately 7,000 generic cells, and I want to make sure I'm not wasting my time.
Wolf likes this post
Formerly known as Dallski
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#16
Thank you for the charger model suggestion Wolf, but I can't find it on sale in my county.
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#17
(02-08-2019, 06:20 AM)Dallski Wrote: Shawndoe, that was my first choice, I might try that for run #26 tomorrow.

.......... as long as you dont mention internal resistance...j/k. ........

But on a serious note, even though the temperature is not extreme, it can make a big difference in the number of cycles a battery can get (I'm thinking Nissan leaf air-cooling vs Tesla liquid cooling) I just dont want someone to discredit my results on the fact that the genuine LG battery was subject to the highest temperatures. Also, I don't believe any of these cells have a data sheet, which is part of the reason I'm collecting this data. Unlike a lot of "data," I see from people selling stuff (batteryhookup, for example), I am in no way selling anyone anything. This is mostly for me, and I'm trying to share with the community because there seems to be a lot of fear and negativity toward generic cells, and I want to see if that is unfounded. I'm going to be building a powerwall out of approximately 7,000 generic cells, and I want to make sure I'm not wasting my time.
Dallsky

I will try not to mention **  Tongue


Sharing with the community is what's it all about and I applaud your efforts. I am looking forward to your results.
I also have "several" generic cells and after measuring ** and finding a very promising number I did run these cells through a test and was very surprised to see the outcome. So obviously there are some generic cell manufacturers that take pride in what they produce and aren't out to scam us.
So you taking a look at these cells being plausible to use is a great undertaking. I will expect reports on a regular basis. Big Grin

Wolf


(02-08-2019, 07:49 AM)Overmind Wrote: Thank you for the charger model suggestion Wolf, but I can't find it on sale in my county.

That's too bad. I do make a trip to Austria every summer so I could buy one and ship it to you when I get over there. Austria to Romania shipping can't be that bad. And the iCharger works on 12V DC so no worries about grid V. Come to think of it most all charger/testers are 120V 240V auto sensing.

Let me know if you want me to do that.

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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#18
I have been updating the first post so that people don't have to search through the whole thread to get information about my test. In summary, I have now completed 105 cycles, and have seen less than 1% degradation in my generic cells, and less than 3% degradation in the genuine LG cell. I'm going to keep going with this test for at least the near future. Check out the first post for more details and charts. Fun fact, if you add up the charge going into the cell and the charge going out of the cell, each cell has already seen at least 1.5kWh of electricity pass through it.
Formerly known as Dallski
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#19
Very impressive test and interesting results. I harvested a lot of these generic cells lately and will happily put them into my wall.
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#20
Thanks for the feedback! The test is still not done yet, so I can't yet confidently say if they should be included in a powerwall or not. I hope to do 500 cycles, but I will inevitably get bored of the test or the charger will give up, or something else, so I'm cautious about overpromising and under-delivering. Whenever I'm done cycling these cells, I will destroy them either with a 12V charging test or with a short-circuit test to test their safety. There are many types of generics and some are better than others. I would not include YLE cells as I probably have 50 of them from several different packs and all are leaking and rusty. That is the only generic brand I can confidently say is junk.

All I am saying is that you should proceed cautiously when using these cells. There must be a reason why people are so scared of them, and I'm really trying to find out why.
Formerly known as Dallski
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