Results of Capacity Testing 18650s for 1,600+ Cycles

[Generic]

**Go to the bottom of this post for my most recent results** 1,605 cycles as of August13, 2020

I'm going to be dedicating one of my Opus' to longevity testing some cells. It has 4 slots, so I am going to be testing 4 cells. Originally, I was going to only test generic cells, but I came up with the idea of testing a genuine cell as the 4th cell to act as a kind of "control." The "Generic" cells will be the ones that I have the most of: (1) CJ blue 2000mAh cells; (2) ASO purple 2000mAh cells; and (3) THLD blue 2000mAh cells. These are all new-old-stock cells from around 2011.The fourth cell will be a genuineone that was originally rated for 2200mAh and tested with almost new capacity. I was thinking of using either an LGAAS31865 from 2010;a Samsung ICR18650-22F from 2012; or a Sanyo UR18650A from 2015. I'd rather avoid using the Green Sony's or red heater Sanyos from before Sanyo was bought out by Panasonic. I'm leaning towards going with the Samsung, but let me know if you think some other cell would be a better representative of the "genuine" cells most people use for their power walls.

I'm going to use the Charge Test function at 1000mAh and record the capacity for each of the cells after each cycle. These will all be full cycle 4.2V to 2.8V discharges, so it's a lot more abuse than a typical powerwall will give these cells, but it will also help speed up the results. I'm going to aim for at least 100 full cycles.

I know that many people open up generic packs and are surprised that cells are testing at their rated capacity. I also know people question their longevity like in the articleMike/LithiumSolar cited posted by BatteryHookup. Also, I think hbpowerwall was longevity testing some Chinese cells, but I don't know what happened to that.So I'm hoping to, as scientifically as possible, give an answer to the age-old question: "Generic" Cells, are they ok to put in my powerwall?

Let me know if there is anything else I should consider before starting this test. Once I start cycling, I'm not going to make any changes.

---

EDIT: (1/30/19)I ended up going with the LG battery for the genuine cell. The Samsungs retested below 2000mAh and I want to keep the capacities as close as possible. Also, adding a picture of the cells being tested and their first capacity test.





EDIT: (2/11/19) Started cycle 34 this morning and after breakfast came back to find the Opus fan not working. Before unplugging the Opus, I tested the cell temps. They were between 65 and 72*C! One spot on the back of the Opus was 85*C! I guess the overheat protection on this unit is not working because the cells were all still discharging at 1A! So I waited for everything to cool and when I plugged in the Opus, the fan kicked on again like normal. Anyway, I went ahead and discharged the cells and entered an asterisk in the log for cycle 34. Hope the high heat doesn't affect the test results.

EDIT: (2/12/19) For cycle 35, I ran a 120mm computer case fan blowing air over the cells from right to left. I was worried that the Opus fan might not come on, so this was mostly for backup. Well for this cycle, I thought either my Opus was toast, or the cells were permanently damaged, because Cycle 35's results, as compared to Cycle 33's results went like this: LG - 3.8% lower; CJ - 3.4% lower; ASO - 3.0% lower; and THLD 3.8% lower. Then for Cycle 36, I took the case fan away, and ran the test like normal. Results were back to normal ranges, and for Cycle 37, were almost identical to Cycle 33 (within 1mAh!). So looks like no permanent damage to either the cells or Opus. I'm carrying on with the test just like before. I'm just really shocked how much cell temperature can make a difference to the test results!

EDIT: (2/17/2019) Hit a milestone today, 50 cycles complete! Took a little longer than I'd like, but I'm making progress. Cells are changing slots again in the morning for Cycle 51. Nothing else new to report.

EDIT: (2/27/2019) Currently running my 79th cycle! That's like over a kilowatt of electricity put into and taken out of eachcell :-DMy new ETA for results of 100 cycles is Saturday, March 9th, 2019. Not really an update, but I did look at the LG datasheet, and turns out I'm testing it like they recommend, go figure! 1 Amp charge and 1 Amp discharge, but they do say to test at 500mA to get true capacity? The data sheet says that the LG Battery should have greater than or equal to80% of its capacity after 300 cycles, not 500 like other name brand cells are good for. This was not a new cell, it had about 90% of its capacity left (2200mAh * 0.9 Opus correction factor = 1980mAh?). Based on that, it should lose about 6-7% of its capacity during this test by Cycle 100, and be at about 2070mAh. We will see!

EDIT: (3/9/2019) As promised, here are the results!! I have run 105 cycles, 5 more than the 100 set in my goal. The reason for that was to get an average of the first 5 cycles and the last 5 cycles, and compare those. Because I was switching slots every 25 cycles, the heat on the right 2 cells was affecting the results a little. Cells have more capacity at higher temperatures, and a few degrees Celsius seemed to make a little difference. That's why I used the averages ofCycles 101-105 in comparisonto Cycles 1-5, as those cycles were all in the same slots. Ok, here are the results:









And the degredation:




So with that, obviously, I have to run this test to at least 205 cycles or until I get bored of it. And it seems like I have more questions than answers at this point. To me, I'm not surprised the LG lost the most capacity. It started this test at about 90% capacity when you factor in the tester correction factor. Also, according to the data sheet, it is one of those 300 cycle rated cells, not a 500 cycle one. I was expecting 6% degradation to be honest, so it did better than I thought it would. Now onto the generics. Why did they do so good? Is my Opuswearing out or something? It was surprisingly consistent throughout this whole test. The jagged lines on the charts are only because my resolution is between 2100 and 2220. If it was 0-2200, it would appear very smooth. I have some theories about why generics and regular laptop cells die fairly quickly. Mainly (1) keeping them at full charge most of the time, which I have seen in other tests that itabsolutely kills the cells quickly; (2) temperature in a laptop is usually pretty warm as there is usually no active cooling for batteries and computers are known to generate heat; and (3) especially in generics, the BMS's are terrible. Almost every generic pack I have opened uses thin gauge aluminum wiring, nickel-plated steel for nickel strips, some lack a thermister for temperature monitoring, and the spot welds are usually really easy to remove and countless packs have a disconnected cell in them. Bad quality control might be why people avoid generic packs. But the cells seem to be well manufactured. Time will tell.I will have to keep this test going to see if capacities will fall off a cliff. Or maybe, just maybe, generic cells are actually good. P.S. I did take pictures of every cycle's results and I have the results of every test written down, if anyone is interested, I can upload that as well.

EDIT: (4/2/2019) Just wanted to post an update that this test is still going and I'm running Cycle 175 as I type this. I was going to do an update around Cycle 130 but didn't feel I needed to. Around Cycle 130, the spring furthest to the right on my Opus started sticking a little and I missed one result. Cell fully discharged and a few minutes into the recharge, it went "null." Happened a couple times, but the other times I wrote down the results before taking a picture. Anyway, I took apart the Opus, put a little dielectric grease on the track, and everything was fixed. It's been uneventful since that time. I'm starting to see some degradation in the THLD cell, and the LG has declined the most, but I was expecting that since the LG was a previously used cell not at 100% capacity when the test started. Anyway, I'm hoping to post the next set of results by April 15th.

EDIT: (4/15/2019) Ok, it is time to release the next set of results. Finally seeing some degradation! Here's the chart:



And a little closer look:




You can see a definite trend. Just going to repeat a few things if you don't want to read from the beginning. Since I am rotating cells every 25 cycles, and the right two slots get warmer than the left two slots, when a cell is on the right side, it benefits from heat adding capacity, and when it goes from slot 4 to slot 1, the capacity takes a hit. Also, the missing data for the THLD cell in Cycle 129 is from the slot being sticky and going null on the recharge. I didn't get a reading, but when I took the cell out and put it back in, it was at 3.29V, so I know it had gone through a full cycle. Also, because I am rotating every 25 cycles, I wait until 5 cycles into the next rotation to compare to the first 5 cycles, so that there is no slot selection effect.

With that being said, here is the degradation observed over 205 cycles. The first row is the average of Cycles 1-5 and the second row is the average of Cycles 201-205 for each cell. The third row shows the percentage of degradation of eachcell.





Please keep in mind that the LG cell did not start out this test as a new cell, and already had a number of cycles or cycle equivalents on it before the test got started. The other cells are 8 year old cells that were never used. And as most of usknow, degradation is not linear, it accelerates.

Anyway, I'm continuing this test. I just finished Cycle 213. I would have posted this earlier, but I didn't really have a chance.

EDIT: (6/3/2019)Sorry for my leave of absence, it says my last login was the 22nd of April. Ouch. Just took a break from this forum and used forum time for other stuff. I did keep this test going. I've dedicated my Opus to this test for 1/3 of a year now. Wow. Yes, I just finished my 350th cycle! Didn't think I would make it this far, but I'm really glad I did. Here are some results:









And here is the degradation (second number is Cycles 301-305)as calculated by the method mentioned by Wolf back in April. Makes more sense to do it this way. Assuming I reach 405 cycles, I will use this same formula.





It seems the more data I gather, the more questions I have. Like, why am I seeing such small degradation? Is there something wrong with my Opus? With my testing method? For example, the data sheet for the LG cell rates the cell as 80%+ remaining capacity after 300 cycles. The LG cell that I'm using in this test came from a used Laptop pack that had an unknown number of cycles and cycle equivalents. And yet, 350 cycles after an unknown number of previous cycles and like 8 years after the cell was manufactured, the LG cell is still doing great! Oh and the generic cells are not doing bad either. I mean the THLD cell has seen 6% degradation, and Cycles 348-350 were the first times this cell saw less than 2000mAh, but this is like a generic cell that nobody has heard of, unlike a number of people who have CJ or ASO cells. I was expecting 100 cycles before this cell was toast and it's nothing like that.

EDIT: (6/23/2019)Time for an update! Just finished Cycle 405, and here are the usual charts I post. I can see that the CJ cell is starting to accelerate its degradation, but the LG and the ASO are still doing great!









And here is the degradation chart:





I feel like I really have to go for 505 cycles just because 500 seems to be the magic number that most cells are rated for. Will also probably put together a video with pictures of all the cycles once I hit that mark.

On a side note, I also started safety testing my generic cells. Not the ones used in this longevity test, but other cells from the same manufacturers. I finally learned what PTC does when I was testing for CID. Turns out that when you try to short out a cell, or use it for a higher discharge rate than what it is rated for, you will not trigger CID, but rather PTC. I was getting strange results shorting my cells, but that was the PTC protection working. Spoiler: CJ and ASO have PTC protection. I'll save the rest for another thread in the future. Stay tuned!

EDIT: (8/10/2019)505 Cycles! Here are the results:







And the degradation:




One thing that these capacity tests do not show is IR. Even though the LG cell is doing pretty well, it definitely has the highest IR. It takes the longest to charge, and it has the highest "bounce" voltage on the first test in the morning. The THLD cell, though it lost a lot of capacity, still has the tightest voltage and is the fastest to charge. I could literally do 4 tests a day if it was only the THLD cell, but the LG cell is slowing me down. It's getting to the point that I have like a half-hour window to take a picture of the third result of the day between when the THLD cell is fully charged after its third cycle and the LG cell finishes discharging its third cycle.

EDIT: (9/9/2019) 605 cycle update: Degradation on the CJ and THLD cells looks like it is accelerating. The LG and ASO cells are still degrading fairly linearly. The test is getting a bit slower, I'm doing about 2 cycles a day instead of the usual 3 cycles. I'm going to continue this test, but I'm starting to get a bit fatigued by it. I have been doing this since January!













EDIT: (10/14/2019)Update time! 705 cycles. Chart is self-explanatory. We are now past the 70 or 80% that every datasheet I have ever seen usually stops at. I am also re-uploading the degradation numbers at each 100 cycle interval. I was doing the math with the Wolf method, but was getting over 100% degradation, so I'm reverting to how we all do state of health: tested capacity over initial capacity. I'm starting to wonder if the THLD cell will make it to 805 cycles? I'm also considering changing the Title of this thread to "Long Term Capacity Testing Cells." I think a lot of people who would benefit from this information are skipping over this thread because they have an uninformed negative bias toward generic cells (I used to be one of those people).













EDIT: (11/24/2019)


First cell to be completely degraded: CJ! It has been testing under 100 mAh since Cycle 776, but it is still putting out about 64 mAh for 30 straight cycles. I think I'm done testing this cell at 1000mA, so now that I have an official number for Cycles 801-805 for my data, I'm going to run the cell at 500mA discharge for Cycle 806 to see what capacity it has at a lower discharge rate. And maybe 300mA for Cycle 807 and 200mA for Cycle 808 if it doesn't take forever. Then after Cycle 808, I'm going to fully charge it at a 200mA charge rate, and test its voltage at weekly intervals to see if it self discharges. The THLD cell looks like it's going to be fully degraded pretty soon, too, so I think I will do the same thing to it after 5 or 10 sub-100mAh cycles.










You may notice that the ASO and LG cells seem to be dipping quicker than before, but I don't think they are degrading any faster. I think they are showing lower capacities because the CJ and THLD cells are not generating heat next to them like they did before. I wish I had temperature correction like rev0's equipment, but I don't, and this is one of the downsides of the Opus.

Also, like any true research, data creates more questions than it answers. For instance, the THLD cell started dropping capacity much earlier than the CJ cell, but the rate of decline was flatter. The CJ dropped like a rock, from about 1000mAh to <100mAh in just 75 cycles. Could it be the chemistry? Electrolyte? Cobalt content? Age?





I also wanted to post this chart. It shows how much energy each cell has stored in its lifetime. The CJ cell was able to store 5 kilowatts of energy in its lifetime!

Lastly, I just want to mention that I have received the cell cycler from rev0 and am excited to start another long-term test after I do some other testing like high-drain generics and possibly some end-of-life (50% of original capacity) genuine cells to see their degradation much more quickly than with new cells. We'll see. Stay tuned?

EDIT: (2/5/2020)I've finally hit over 1,000 cycles. Took 53 weeks, but here we are! And sorry for not updating at 900 cycles, I had everything ready, but it was right as the New Year hit, and I never got around to posting it. Right around 900 cycles is when the THLD cell ran out of steam, so I ran that one up to Cycle 922. Cycle 923 was at 500mA and it tested at 190mAh; Cycle 924 was at 300mA and it tested at 300mAh; and Cycle 925 was at 200mAh and it tested at 402mA. Anyway, here are my usual charts:













Also, I know someone asked if the cells were self-discharging. I have been taking measurements of the voltage of the CJ and THLD cells every 25 cycles and there's not much of a story to report. As of February 4, the CJ cell is still sitting at 4.15 Volts, and the THLD cell is also at 4.15 Volts. They are not self discharging at all, despite being end-of-life cells.

I'm coming to the conclusion that the ASO cells are most likely OK to mix into a powerwall with LG, Samsung, Sony, Sanyo, and BAK cells. They seem to have decent Cobalt content, at least on par with LG's value cells. I'm also pretty sure they are not manufactured by Samsung, as is commonly believed. They are just too different with the positive cap and with the top cell crimp. Lastly, I have verified that they have both PTC and CID protections, so they are on par with genuine cells with regard to safety, capacity, and lifetime.

EDIT: (4/12/2020)Update time! Sorry I never got around to posting at 1100 cycles, I had everything ready, but didn't get a chance to log in here and post it. Here is the degradation chart, at least:





So, I have made it past 1200 cycles! Right at Cycle 1175, the Opus fan finally gave up (it was moving, just not enough to remove much heat), and you can clearly see a spike in the results. I have several replacement fans on hand, so it didn't cost me any time. Otherwise, it's been pretty uneventful. The THLD cell is sitting at 4.13V and the CJ cell is sitting at 4.14V after almost 4 months, so they are not self-dischargers, despite being end of life. I'm not going to be checking those voltages anymore. The ASO and LG cell are continuing their very slow, almost linear, decline. On the one hand, I'm wishing they would just die already so I can end this test and not feel guilty about ending it early, but on the other hand, I'm rooting for these cells to keep going because the results of this test are so much bigger than the fate of 2 random cells. Anyway, here's where we are at:









And the degradation:





EDIT: (6/19/2020) I skipped the update at 1300 cycles, but here I am at 1400! Here's the graph:





And where we are at SoH:





I also set out to see if degradation is linear or exponential. The CJ and THLD were clearly exponential. The ASO and LG cells, I'm not sure. Here is a chart showing the rate of change. For example, the data point at 200 is the % increase in degradation from Cycle 201-205 over the degradation in Cycle 101-105, and so on. The LG looks fairly linear, while the ASO seems to be going exponential.





EDIT: (8/13/2020)First off, I made a mistake. I write down every result on a notepad, and then do data entry into excel when I hit a milestone and am ready to report an update. Well, for some reason, I wrote Cycle 1528 twice (...1527, 1528, 1528, 1529...). What I decided to do is average the results of the 2 cycles and use that number as the entry for Cycle 1528. To make up the test cycle, I will skip over Cycle 1666, assuming I get to that point, because I don't like that number :angel: .

Second, I kind of discovered something that I wanted to run by the community. I never really paid attention to the THLD cell's "INR18650" designation, as I understand that INR/ICR/IMR/NCR don't actually signify chemistry and are just naming conventions, but it got me thinking. If the THLD cell is labeled as an INR cell, and it actually is an INR (Lithium Manganese Nickel) vs. being an ICR (Lithium Cobalt Oxide), then the results of my degradation testing don't signify quality, but rather chemistry. It's not that the CJ and THLD cells are Chinese junk, but rather, they are low-cobalt-content INR cells that typically have a shorter life than their cobalt-rich ICR cousins. That also got me thinking again. If the CJ and THLD cells were truly INR cells, why did their PTC protection kick in to limit their short-circuit discharge to just 2 amps and why did the cells still heat up at that low of a discharge rate? My theory is that, since much of the cost of INR cells comes from having thicker copper and aluminum collectors, the Chinese manufacturers used thinner current collectors, while also using the low-cobalt INR chemistry. That would explain how they got their cost down. So high discharge chemistry without the ability to do high discharge. What do you all think about that theory?

 

[daromer]

Its 1000mA not mAh

What you need to take into account is that the Opus is not consistent. Not between cells nor between the slots and you can get different results each time. For instance the contact surface do create some issues. So when testing for getting a result you need to remove the variation

So for doing the test I highly recommend to first test all cells atleast 3-5 test on a high end tester to know their baseline and then do same on each slot to know the slots baseline.

If you skip this the variation or what you need to remove from the end-result will be bigger

Hope you get the information above.
Good luck!

 

[Wolf]

I'm not sure the OPUS is that faulty I have done repeated tests with it just to satisfy my curiosity.
The biggest fault the OPUS has is its IR measurement that is way off but as far as capacity measurementconsistency per slot and per battery I don't find that much of aproblem here. The BT3100 V2.2 correlated with my tester results of before and the min max difference is almost negligible.
Here is my sheet of results. Again the proof is in the documentation not in the conversation.



Now maybe I got the testers that were built in the middle of the week not on Monday (hangover day) or on Friday (can't wait to get out for the weekend)
but these are the results I am getting.

Don't let the numbers get in the way of the facts.

Wolf

 

[daromer]

The Opus is manufactured on soooo many places and in so many variants and I have seen sooo many different results... Once again it depends on what you compare to. I would say it can diff up to 10% or so easily. In your document you have atleast 5% or something I think? (Without checking)

Im not going to show something up here but you can never trust a source into its decimal part like 1mAh that the opus show and then think its accurate down to that. Thats what im trying to say... You Always need to build in a variance like in your test you have 5% then you need to scale away everything that doesnt fit into that.

The more itterations you run your numbers the larger the error is every time so if you start with 5% error and you then redo the test with another factor you have another 5% added... And so forth

Does it make any difference in the end? Depends... For instance testing 2.2Ah cell and you get a result out that is 2150mAh.. Does it state it degraded? No it doesnt if you have a 5% variance. Its just within the limits and perfectly fine. Thats the deviation line you need to set

The only reason i sort based on 100mAh is because I have not established a baseline and deviation. The 100mAh deviation policy have prove to work great as long as you random the cells The end result have been below like 3-4% deviation between each built pack and thats better than i have seen on the Opus itself. Luck perhaps?

Sorry for the ramble Im just making sure that noone get burned hoping the opus does 0.5% variance results

 

[Wolf]

Daromer
OH believe you me I know exactly what you are talking about.
As you know I have done a bunch of testing with these testers and have come to the conclusion with the results we get there is always going to be a certain deviationwith the testers themselves. No matter which one is used . I am now testing the iCharger x6 and will have the results in the near future.
I no longer test with the Zanflair as you know because it has really inflated results. I am going through all my previously tested cells and the Zanflair is definitely way off. Foxnovo is slowly becoming my favorite. Simple does the job and accurate. If anything it's a little (very little) onthe low side.

Dallski
I am looking forward toyour test and hope you will record and share the results with all of us.
Just for a baseline on your OPUS that you are going to use run 1 cell through all 4 slots and see how much difference you get. I am curious as my deviation between slots was less than 5%.

Onward forward never straight.

Wolf

 

[Korishan]

As you know I have done a bunch of testing with these testers and have come to the conclusion....

Not good enough! Do all the tests over again to make absolutely sure without a hint of doubt that the previous results could possibly be somewhat as accurate as perhaps the second somewhat inconclusive or sub-conclusive random results. We need repeatable data here!

 

[Wolf]

As you know I have done a bunch of testing with these testers and have come to the conclusion....

Not good enough! Do all the tests over again to make absolutely sure without a hint of doubt that the previous results could possibly be somewhat as accurate as perhaps the second somewhat inconclusive or sub-conclusive random results. We need repeatable data here!

LOL I will never get my powerwall built if all I do is test the testers. Oh wait a minute I am testing the testers or is it the batteries I'm so confused.

Wolf

 

[daromer]

We should not OT this thread any more. As long as we all agree that there are a deviation on the cheap testers for instance the pressure or corrosion will cause different values Im happy. That will make sure that we have the proper info we want and people doesn't get dissapointed when tests are done.

 

[Generic]

Glad I inspired a good discussion on testing equipment! I've read through a lot of threads on accuracy and Opus hacks and have come to a simple conclusion that I think we can all agree on: these testers are "good enough" for us. If we were all doing 1P packs without balancing, accuracy would be paramount. But with so many cells in parallel, it is only important to get close. Especially since all the cells we use are at different stages in their lifetimes, pack capacity can literally change in a few cycles.

With that being said, I was going to test each cell in the same slot, which would negate any slot-to-slot variance.

I'm not really looking at absolute numbers, but a capacity curve. Kind of like a 100 day moving average in investing. You dont look at the day to day ups and downs, just a larger overall trend.

Also, I'm testing in a climate controlled room, so temperature should not play any factor, or if it does, it will affect all the cells equally.

Again the whole point of this test is to see if generic cells are really junk or if they can be useful in powerwall applications. I'm testing 3 different brands of generics, but manufacturing could vary day-to-day even within the same brand. I would have to test a much larger sample with more accurate testing equipment to get a definitive answer. But I'm just going for "good enough." Thank you for all your input!

 

[Overmind]

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.

 

[Wolf]

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 settingsand so do a lot of other "Professional" units.
The question is if you are testing hundreds if not thousandsof individual cells all you are trying to get is an idea of capacity.
That is a little difficult testing1 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

 

[Generic]

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?

 

[Wolf]

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.

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 Opusor at minimum in the middle at the top. Maybe a tad bigger wouldn't have hurt it either. Shiftingthe cells sounds like a reasonable idea as to see if temp of the cells screw the resultsa 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 dischargedat 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 isat 0.5C and discharge at 0.2C.

Those are my thoughts.

Wolf
Dam I didn't mention IR anywhere.
Oh yes I did.

 

[Shawndoe]

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.

 

[Generic]

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.

 

[Overmind]

Thank you for the charger model suggestion Wolf, but I can't find it on sale in my county.

 

[Wolf]

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 **


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.

Wolf

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/testersare 120V 240V auto sensing.

Let me know if you want me to do that.

Wolf

 

[Generic]

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.

 

[stevelectric]

Very impressive test and interesting results. I harvested a lot of these generic cells lately and will happily put them into my wall.

 

[Generic]

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.