Li-ion cells cycle ageing

[Dak77]

Now that I've seen how awesome the M36 is , it makes me wonder how it would handle 5-7A.

The miraculous this cell is not. At 3C continuous it wear out in just 100 cycles.

That reminds me. I remember you posting about the M29 a bit . Between all the 2900mah , is the 29e best equipped to handle 2c loads frequently?

 

[eMark]

NCM versus NCA: Lithium ion’s fork in the road

Benchmark Mineral Intelligence forecasts that NCM batteries will make up 70% of the total global lithium ion battery market by 2026. NCA has been far less widely adopted and the main proponent remains as Tesla. With NCA the lines are a little more blurred as the technology does not have the clearer raw material proportions that we are used to with NCM.

Nonetheless behind the scenes, Panasonic, Tesla and their cathode suppliers have been working tirelessly to reduce their cobalt dependency, not only to push the cost of the battery down but also over supply security fears.
https://www.benchmarkminerals.com/panasonic-reduces-teslas-cobalt-consumption-by-60-in-6-years/

These cycle tests by docware would seem to confirm that Erik's decision to cancel his NKON PanasonicPF order for 112 cells (8P14S) in favor of LG's M36 cell was a good decision as further supported by docware's cycle tests ...

https://endless-sphere.com/forums/download/file.php?id=261775 (LG Chem M36 - 200 cycles)
https://endless-sphere.com/forums/download/file.php?id=261800 (PanasonicPF - 200 cycles)

https://endless-sphere.com/forums/download/file.php?id=261889 ( LG Chem M36 - 250 cycles)
https://endless-sphere.com/forums/download/file.php?id=261888 (PanasonicPF - 250 cycles)

https://endless-sphere.com/forums/download/file.php?id=262464 (LG Chem M36 - 300 cycles)
https://endless-sphere.com/forums/download/file.php?id=262431 (PanasonicPF - 300 cycles)

SanyoGA's DCIR isn't doing any better than PanasonicPF's DCIR (both NCA chemistry)
Samsung INR18650-29e 2900mAh - 8.25A ... DCIR is looking very good (INR is NCM chemistry)

Samsung INR18650-30Q 3000mAh - 15A (NCM :thumb ... if and when tested by docware the Samsung 30Q should also have a lower DCIR than either PanasonicPF or SanyoGA (NCA).

 

[Cephalotus]

Samsung INR18650-30Q 3000mAh - 15A (NCM :thumb ... if and when tested by docware the Samsung 30Q should also have a lower DCIR than either PanasonicPF or SanyoGA (NCA).

Cycle tests are only half of the story.

In the German Pedelecforum the 30Q now has a very bad reputation for larger packs. It seems that 9 out of 10 packs fail after just some months of use, because single cells of 30Qs do develop heavy self discharging:

https://www.pedelecforum.de/forum/index.php?threads/akku-pack-mit-samsung-30q-l%C3%B6ten.45011/

 

[eMark]

It seems that 9 out of 10 packs fail after just some months of use, because single cells of 30Qs do develop heavy self discharging

Can we trust German Pedelecforum single cell vaper/pedalers? That's what happens when using 9 out of 10 30Q packs for unhealthy single cell 30Q use :wink: Maybe those ePedelers were under the impresson from Banggood that the 30Q had a 20A rating or maybe some of the 30Q cells were fakes (via LiitoKala Ali) ... http://budgetlightforum.com/node/60547

"Here are the results for an abusive life cycle test of three popular 3000mAh batteries. The Sony VTC6 was the best performer in my original testing but does it have a weakness? Is it a cell that can't take abuse? The datasheet specs seem to indicate that it might have a shorter cycle life than the other two." https://www.e-cigarette-forum.com/threads/bench-test-results-which-lasts-longer-vtc6-30q-or-hg2.807131/

Test Conditions:
Eight 30Q's, eight HG2's, and four VTC6's were tested. Each battery was subjected to fifty charge-discharge cycles at rates designed to accelerate their aging. Charging was done at 4A to a cutoff of 4.20V @ 200mA. Discharging was done at 15A continuous down to 2.50V. This brought the temperature of each cell up over 80°C for each cycle. Each battery was only rested for sixty seconds between charging and discharging. I estimate that this accelerated life-cycle testing aged each battery the equivalent of at least 200 cycles.

Bottom Line: The VTC6 started with the highest capacity but the 30Q had the smallest loss of capacity after 50 abusive charge-discharge cycles. The HG2 was the loser in these tests, having the lowest starting and finishing capacity." ... https://www.e-cigarette-forum.com/attachments/img_5603-jpg.663327/ (chart)

Soooo, are we to conclude that the Samsung 30Q was designed more with vapers in mind than ebikers

Can we move on from the German single cell epedalers and get back to real-life 30Q ebiking :thumb:

 

[john61ct]

Such comments, and especially the attitude / personality revealed by them, really are harmful to constructive cooperative discussion in an open forum.

Whether EVs, boats, vapers whatever, data from objective tests is **much** more valuable than walls of text scraped from commentary around the web.

 

[Cephalotus]

It seems that 9 out of 10 packs fail after just some months of use, because single cells of 30Qs do develop heavy self discharging

Can we trust German Pedelecforum single cell vaper/pedalers? That's what happens when using 9 out of 10 30Q packs for unhealthy single cell 30Q use :wink: Maybe those ePedelers were under the impresson from Banggood that the 30Q had a 20A rating or maybe some of the 30Q cells were fakes (via LiitoKala Ali) ... http://budgetlightforum.com/node/60547

I'm just providing Information. Most of the cells have been bought from Nkon and most cell packs have been made by people that have built cell packs with other cells that behave just fine.
We are also not talking about one person or two, but a significant amount of numbers.

Some people have been very happy with the 30Q at least for some weeks until their packs got faulty, too and it does not affect all cells, maybe "just" 5-10 cells out of 100 (this is a wild guess), but sadly if you build packs with 50 cells and more your chances are very high that you will have faulty cells. Faulty means in that case the development of very high self discharge rates, something you will not be able to notice on a cycle test of single cells like the one discussed here.

Those cells fail one after the other, so repairing the packs doesn't help.

So this is the story about 30Q battery packs in the German forum.

If the 30Q is your prefered cell you don't need to defend it against me. If you want to use them just go ahead, I'm perfectly fine with that. I don't have a hidden agenda to promete any cells, we all are trying to learn.

---

Some people are desperate to identify "winners" and some people develop blind spots after identifieing their chosen winner.

I do read as many aging tests as I can find on 18650 cells and I do like the tests here. They can contribute to the bigger picture.

I don't try to fine "the best" cell, because this is very difficult. It takes 4-6 years after introduction until the aging charactzeristic of a cell gets clearer, so for the newest and maybe best cells you don't have sufficient data.

For me chosing a "good enough" cell is good enough And good enough always depends on your personal specifica. Running BionX Systems year around for my Needs a cell must survive short cahrging Bursts at high current even in cold state because of regen. This is a very special feature which is almost never tested and which could be able to kill some cells very quickly.
Your cells may need to survice very different challanges.

 

[docware]

Some people on the Pedelec forum mentioned soldering as a root cause of the issue.

 

[eMark]

Some people on the Pedelec forum mentioned soldering as a root cause of the issue.

Fortunately you read German ... wasn't sure if he was being a litte facetious (single cell), so brought up the subject of vaping (i'm not a smoker or drinker). You may have also noticed that when googling VTC6 (or HG2) vs 30Q some of the google comparisons are about vaping. Makes one wonder if as many of these 3000mAh 15-20A cells are sold to vapers as ebikers? Seems to be a tossup as to which cell is better whether for vaping or a DIY pack build ... but maybe these 3000mAh 15A-20A cells aren't the best cells for a 8P14S DIY ebiking build ?

"I use the Sony VTC6, as well as the Samsung 30Q. The VTC6 are slightly better cells. Their internal resistance is lower, and they have a bit less voltage sag. They also have about 4% more energy. But, overall, they’re very similar to the 30Q, and you’d probably not notice any difference.

For the ones you mentioned I would choose 30Q. I have had personal experience w/ VTC6 and LGHG2 degrading at a higher rate than 30Q."

Deciding which 3000mAh 15-20A cell to use for a sizeable DIY triangular bike pack usually comes down to cost (8P14S 112 cells). Currently at IMR in quanties of 100-199 ... VTC6 $4.85, HG2 $3.25, 30Q $3.85.

One might ask why Luna doesn't offer the VTC6 as an option in their 52V Wolf pack instead of 30Q or MJ1? Does it basically come down to the bottom line of cost savings even though VTC6 has a 20A rating to 30Qs 15A rating (so big deal).

Reminds me of the good ol' days when it was all about V8 horsepower between Chevy and Ford. Now it's about mAh capacity, amp rating and NCA vs NCM originating from Japan, South Korea and China. No longer America

 

[Pajda]

Now that I've seen how awesome the M36 is , it makes me wonder how it would handle 5-7A.

The miraculous this cell is not. At 3C continuous it wear out in just 100 cycles.

That reminds me. I remember you posting about the M29 a bit . Between all the 2900mah , is the 29e best equipped to handle 2c loads frequently?

Actually it is not. Present number one is LG M29. It can handle 3C continuous (single cell on free air) "with the finger in the nose". At the setting: 0.5C charge - 3C discharge at 100% DoD it have still ca 88% of initial nominal capacity after 900 cycles. But more important the DCIR rise is only cca 52% (100% DCIR rise is comonly considered as EOL). If you compare only capacity loss with the 29E7, it have ca 86% of initial nominal capacity after 900 cycles. And so one say that they are even. But this is exactly the situation, where you need to track the DCIR rise, because the 29E7 DCIR rise after 900 cycles is 297% (twohundredandninetyseven)!!! If you ask how it is possible, you need to see the discharge graph (which I can not show you). From the graph you will clearly see the significantly higher voltage sag for 29E7, but 29E7 holds the voltage better at the end of discharge rather than M29, so it compensate the higher voltage sag by its capacity below ca 3.1V. But this is quite useless for traction app.

The main problem with the high DCIR rise for 29E7 (and many other cells excluding LG production line) is by my opinion caused by 0.5C charge rate. I expect that at 0.3C charge rate the result will be significantly better.

 

[brone]

Now that I've seen how awesome the M36 is , it makes me wonder how it would handle 5-7A.

The miraculous this cell is not. At 3C continuous it wear out in just 100 cycles.

That reminds me. I remember you posting about the M29 a bit . Between all the 2900mah , is the 29e best equipped to handle 2c loads frequently?

Actually it is not. Present number one is LG M29. It can handle 3C continuous (single cell on free air) "with the finger in the nose". At the setting: 0.5C charge - 3C discharge at 100% DoD it have still ca 88% of initial nominal capacity after 900 cycles. But more important the DCIR rise is only cca 52% (100% DCIR rise is comonly considered as EOL). If you compare only capacity loss with the 29E7, it have ca 86% of initial nominal capacity after 900 cycles. And so one say that they are even. But this is exactly the situation, where you need to track the DCIR rise, because the 29E7 DCIR rise after 900 cycles is 297% (twohundredandninetyseven)!!! If you ask how it is possible, you need to see the discharge graph (which I can not show you). From the graph you will clearly see the significantly higher voltage sag for 29E7, but 29E7 holds the voltage better at the end of discharge rather than M29, so it compensate the higher voltage sag by its capacity below ca 3.1V. But this is quite useless for traction app.

The main problem with the high DCIR rise for 29E7 (and many other cells excluding LG production line) is by my opinion caused by 0.5C charge rate. I expect that at 0.3C charge rate the result will be significantly better.

Why does LG list this cell for 500 cycles at 1.5/4A in their datasheet?

 

[flippy]

Why does LG list this cell for 500 cycles at 1.5/4A in their datasheet?

datasheets are written to make the battery seem as good as they can while keeping it within the intended use case. this is why high drain cells generally have lower lifespan cycles on their datasheet as lifespan is not as important then C rating. for high capacity cells lifespan is more important so you see extremely low C rates so they can push out more cycles and make the cell look better.

if there was a standardized test it would even the playing field. this is why i and some others here spent thousands of american roebels in testing equipement to take out the marketing wank and only deal in raw data that is equal over all cells.

 

[SamRich]

It seems that 9 out of 10 packs fail after just some months of use, because single cells of 30Qs do develop heavy self discharging

For what it's worth (and sorry if a little off topic and anecdotal) , but I have also noticed "single cell" self discharge issue on several 30Q packs including not only with the 3 packs that I have built myself (80-140 cells per pack), but also on two 352 cells packs (88S4P) that I troubleshooted. These high voltage packs were from Samsung portable x-ray cart (so you know these cells are genuine if they are on a Samsung cart) It also had one of the most advanced looking BMS I've seen - multiple balance and control boards. Yet the pack would not stay balanced if left unplugged for an extended period of time- one or two cells would self discharge and make the whole pack unusable.
Here's one of the packs in question:

 

[Cephalotus]

Some people on the Pedelec forum mentioned soldering as a root cause of the issue.

This was the guess at the beginning that they don't like soldering.

But later spot welded packs had shown the exact similar behavior.

 

[Cephalotus]

Some people on the Pedelec forum mentioned soldering as a root cause of the issue.

Fortunately you read German ... wasn't sure if he was being a litte facetious (single cell), so brought up the subject of vaping...

Can be my lack of expressing myself in English.

What I wanted to tell you is that Samsung 30Q cells develop heavy self discharging. Not all cells, but some of them and you can't tell which. Maybe other 30Q batches work better, I don't know. It's just how it is over here with that cell.

when you have only a single cell in your pack with heavy self discharging your battery pack becomes more or less useless, except you keep it on the charger balancing it every day.

You will not discover that fault on cycle tests like this one provided here.

 

[Dak77]

Now that I've seen how awesome the M36 is , it makes me wonder how it would handle 5-7A.

The miraculous this cell is not. At 3C continuous it wear out in just 100 cycles.

That reminds me. I remember you posting about the M29 a bit . Between all the 2900mah , is the 29e best equipped to handle 2c loads frequently?

Actually it is not. Present number one is LG M29. It can handle 3C continuous (single cell on free air) "with the finger in the nose". At the setting: 0.5C charge - 3C discharge at 100% DoD it have still ca 88% of initial nominal capacity after 900 cycles. But more important the DCIR rise is only cca 52% (100% DCIR rise is comonly considered as EOL). If you compare only capacity loss with the 29E7, it have ca 86% of initial nominal capacity after 900 cycles. And so one say that they are even. But this is exactly the situation, where you need to track the DCIR rise, because the 29E7 DCIR rise after 900 cycles is 297% (twohundredandninetyseven)!!! If you ask how it is possible, you need to see the discharge graph (which I can not show you). From the graph you will clearly see the significantly higher voltage sag for 29E7, but 29E7 holds the voltage better at the end of discharge rather than M29, so it compensate the higher voltage sag by its capacity below ca 3.1V. But this is quite useless for traction app.

The main problem with the high DCIR rise for 29E7 (and many other cells excluding LG production line) is by my opinion caused by 0.5C charge rate. I expect that at 0.3C charge rate the result will be significantly better.

Wow. Those are some nice results . I wish a local vendor carried the m29. I'll have to find a good source that ships to the US. - "with the finger in the nose" lol.

 

[Pajda]

Here is another of my unwanted remarks 8)

I need to say something about this test https://www.e-cigarette-forum.com/threads/bench-test-results-which-lasts-longer-vtc6-30q-or-hg2.807131/ revealed by Mooch in 6/2017. I'm not afraid to say that if it wasn't published,the world will be a better place. This is unfortunatelly the example of information which makes more bad than good. There is not a problem in the results themselves. I made tests with similar settings and can confirm that the test results are correct with the Samsung 30Q as a clear winner. The problem is that this particular result leads to generalization that "Samsung 30Q must be then good in other settings as well". I am quite confident that Mooch is another victim of this seductive idea and so he just do not expect that there should be any problem with 30Q cycle life under another, particularly lower test settings. But he cannot be more wrong.

This level of capacity loss at 5C discharge rate should be clasiffied as excellent result. But the major problem is, that Samsung 30Q shows almost identical capacity loss under 3C and even under 1C continuous discharge rate. So at 3C continuous discharge rate its cycle life at 100% DoD is outperfored after just 100 cycles by M29, 29E6, E7 and even Panasonic PF performs significantly better than the Samung 30Q. At 1C discharge rate 100% DoD, the cycle life of 30Q is nothing but total disaster in comparison by almost all cells on the market. The same problem is with its DCIR rise, which is enormous with exponential course. Only narrow 70% or less SoC window helps 30Q to get at least usable results.

 

[Tolkano]

Here is another of my unwanted remarks 8)

This level of capacity loss at 5C discharge rate should be clasiffied as excellent result. But the major problem is, that Samsung 30Q shows almost identical capacity loss under 3C and even under 1C continuous discharge rate. So at 3C continuous discharge rate its cycle life at 100% DoD is outperfored after just 100 cycles by M29, 29E6, E7 and even Panasonic PF performs significantly better than the Samung 30Q. At 1C discharge rate 100% DoD, the cycle life of 30Q is nothing but total disaster in comparison by almost all cells on the market. The same problem is with its DCIR rise, which is enormous with exponential course. Only narrow 70% or less SoC window helps 30Q to get at least usable results.

That's interesting, ive been riding my self built 30q pack for about 6 months now and havent really noticed any capacity fade or increase in sag, but ive literally never full charged the pack since day 1, always have the bms set to cut off charging @ 4v/cell so maybe that has been helping

It would be good to find out what the best cell is out of VTC6/HG2/30Q in terms of capacity fade/dcir rise in regular usage conditions (80-90% DOD, 3-5C discharge)

 

[john61ct]

The problem is that this particular result leads to generalization that "Samsung 30Q must be then good in other settings as well". I am quite confident that Mooch is another victim of this seductive idea and so he just do not expect that there should be any problem with 30Q cycle life under another, particularly lower test settings. But he cannot be more wrong.

This level of capacity loss at 5C discharge rate should be clasiffied as excellent result. But the major problem is, that Samsung 30Q shows almost identical capacity loss under 3C and even under 1C continuous discharge rate. So at 3C continuous discharge rate its cycle life at 100% DoD is outperfored after just 100 cycles by M29, 29E6, E7 and even Panasonic PF performs significantly better than the Samung 30Q. At 1C discharge rate 100% DoD, the cycle life of 30Q is nothing but total disaster in comparison by almost all cells on the market. The same problem is with its DCIR rise, which is enormous with exponential course. Only narrow 70% or less SoC window helps 30Q to get at least usable results.

**Very** interesting!

I was led to believe that relative longevity at high discharge rates would extrapolate to the "more normal in non propulsion" sub-C rates.

This points up a need to run separate cycle-life tests, at least two levels.

If I had the gear and the time, my two questions for testing would be:

Given a cycle between

100% defined as a CC-only charge at 0.3C to 4.1V

discharging to 70% DoD at the bottom, and

EoL cutoff at 70% SoH,

What is the maximum C rate that will support

a 100 cycle lifetime on the one hand, and

500 cycles on the other

 

[docware]

Hopefully I am not annoying too much, if I again recommend to consider Pajda´s posts as a required reading. Just open some text editor and with ctrl C / ctrl V do your own Reader´s Digest.

The quantity of needed separated cycle-life tests starts in my opinion at number 3 or 4 at least, ending somewhere at ….. ?

 

[eMark]

If I had the gear and the time, my two questions for testing would be:

Given a cycle between 100% defined as a CC-only charge at 0.3C to 4.1V discharging to 70% DoD at the bottom, and EoL cutoff at 70% SoH,Sany

What is the maximum C rate that will support a 100 cycle lifetime on the one hand, and 500 cycles on the other

What is "SoH,Sany"? Did you mean to say "SanyoGA." You already know the advantage of a little TLC (500 cycles vs 100 cycles) unless you need to always be present when charging and the sooner the pack is ready the better. Remindful of my RC flying 20-25 years ago. It was also around that same time that 2.5C charging was being adopted as AOK by RC enthusiasts. It was just accepted that normal wear and abuse (occasional crashes) RC pilots just forked out another $50-$75 every few months for another Lipo as part of the fee to have Macho fun flying RC planes. The sooner the better when it came to recharging their Lipo. Some couldn't afford a spare backup Lipo having to buy another replacement Lipo every few weeks. Also, it seemed there was always a newer brand or a Lipo with a little more capacity that they had their sights set on as their next purchase.

The sooner the better was Macho and a few pylon racers (timed relay events) tried charging at even a higher rate than 2.5C as long as their Lipo wasn't to warm to hold in their hand. They figured that if their Lipo could withstand 100 warm discharges at 4C then why not charge it at 4C. Today a 6S TP2250 is only $75, but to replace a Muscle 52V ebike pack that's suffered a premature slow death can cost $700. So, why even consider a 100 cycle life when an expensive brand pack or DIY pack should be capable of at least 400 cycles with a little TLC :thumb:

Docware's SOC % - versus voltage chart ... https://endless-sphere.com/forums/download/file.php?id=261831 ... is insightful for drawing some relative comparisons. For example the 6 cells with a voltage above 3.00V at 0% are:

Samsung 22P at 3.44V
Samsung 29e7 at 3.31V
PanasonicPF at 3.29V
SanyoGA at 3.05V
LG M36 at 3.03V
LG MJ1 at 3.02V
(Samsung 30Q at 2.81V ... the lowest voltage of the ten packs at docware's 0% rating)

The guideline i've decided to use for my 10S5P DIY build using 50 Samsung 30Q cells (serial 141 received yesterday from IMR) is 85% charge (4.05-6V) at 1.5C (have both a 1A & 1.5A 36V charger) and 15% of remaining 30Q voltage (discharged to 3.28V per docware's chart). Also, have a 2.5A charger that came with my Liberty Trike, and may use it when first charging to 50% pack voltage. Fifty percent of a 30Q cell is 3.73V. My etriking is easy going (8-10 mph) with pedal assist for exercise. At my pace it could take three days of accumulated mileage to discharge pack voltage to low cut-off voltage of 3.28V for the Samsung 30Q as shown on docware's chart ... https://endless-sphere.com/forums/download/file.php?id=261831

Appreciate all of your comments about 30Q, so will keep a close eye on these cells. Will switch to balance charging (once a week to begin with) when the pack reaches 79% (4.01V) checking for any cell imbalance in the S-strings and P-groups until reaching 4.05-6V (85%). Like docware and Padja will probaby spend as much time (just my nature) keeping tabs on my DIY Vruzend 10S5P pack. When i was into RC planes years ago got more enjoyment and spent more time modifying and making repairs than the actual time flying planes.

Hoping to get at least 500 cycles on my DIY Vruzend V1.6 (w/copper S&P buss bars & buss wires). Also, the 10S4P Chinese pack that came with my Liberty Trike is still good-to-go with only 80 cycles so will be rotating between the two packs. The Vruzend pack will be in a sealed enclosure (acrylic see-through top and bottom) in the rear trike trunk so the copper won't be exposed to moisture. Was considering a dielectric spray, but probably overkill. It's possible in a couple years if the 30Qs are tempermental i will take out 10 weakest cells and remake into a 10S4P pack (hopefully not a 10S3P pack) but that's the one plus of a Vruzend kit -- easy to disassemble and reassemble.

EDIT Note: Part of the problem may be that the Samsung 30Q is overrated at 15A by Samsung marketeers? Perhaps, a more realistic rating (for most cycle life) is closer to 10A. Was it the LG M36 that was first rated at 10A before being revised to 5A? The BatteryStore rates the M36 at 5.1A. For those looking for a source for the M29e it's in stock at the BatteryStore (Altanta, GA) for $2.90 100-399, they rate it at 2.75A ... https://www.18650batterystore.com/Samsung-18650-Battery-p/samsung-29e.htm

 

[Dak77]

This is derailing the point of this thread . People are putting a lot of personal time into this much needed and appreciated testing and I've probably worn out the subject a long time ago with my 20 different ways of asking the same general questions, so this will be one of my last posts about it ; but I think the point of people buying high rate discharge cells that only hold the majority of their capacity for 100 cycles or so is because they only use their bikes a few times per week and maybe fully charge 2-3 times in a month, so 100 cycles will still get them around 3 years and do it offering very little sag at high rates of discharge. 3 years is a long time in the lithium battery world and it's highly likely a much better cell for lower cost will be available in that amount of time. It took me a while (probably way too long) to fully grasp this, despite knowledgeable people trying to beat it into my dense head. My fixation on long cycle life is finally dying off, as it should. Someone that uses their rig on a long commute to work every day or a power bank will see things quite differently, but the average Joe will likely never need to worry about 1k cycles or even 500.

 

[john61ct]

What is "SoH,Sany"? Did you mean to say "SanyoGA."

SoH is percent residual capacity, State of Health. Industry standard for EoL is 80%, consumers with non-critical use cases can push a bit further.

No idea about the "Sany", and no, I'm not referencing specific makes or cells at all.

I agree that high word-count OT posts are reducing the overall value of the thread. Two ears one mouth. . .

 

[john61ct]

the average Joe will likely never need to worry about 1k cycles or even 500.

Yes, why my two data points were for 100 and 500 only, I think accommodates the many very different use cases without overly complicating the test protocol.

If cell A gets 500 of "those cycles" at 17C, cell B only 5C, then those targeting 250 to 1000 cycles are well served by the comparison.

If B goes to 45C to get 100, but A only makes 40C and is more expensive, that test meets the needs of the group you're talking about.

 

[eMark]

Hopefully I am not annoying too much, if I again recommend to consider Pajda´s posts as a required reading. Just open some text editor and with ctrl C / ctrl V do your own Reader´s Digest.

The quantity of needed separated cycle-life tests starts in my opinion at number 3 or 4 at least, ending somewhere at ….. ?

Docware's reply provided the means to answering john's two questions.

For the sake of discussion let's assume a pack with 3000mAh 10A cells can be charged and discharged at least 100 times at it's 10A rating from 4.1V to 3.3V. Furthermore we'll assume it can be charged 500 times to 4.1V with a 2.5 amp charger (.83C) with worthwhile useable energy for 500 cycles.

So for the sake of discussion we'll assume you can charge the pack 500 times at .83C (2.5A) and discharge it 500 times at .83C (2.5A) over three years of occasional easy-going ebiking without any noticeable voltage sag. So, following that ultra simplistic TLC logic if you want at least 500 charge/discharge cycles over three years don't discharge the cells at more than .83C. Using that KIS logic it's possible to get at least 500 charge/discharge cycles from either a: VTC6, HG2, 30Q, PanasonicPF, SanyoGA and almost any 8P14S 18650 pack and possibly a hundred more cycles :thumb:

Now for those that contend this post is not practical and is derailing the thread then is this thread purely hypothetical bench testing that may not even apply to a real-life daily ebiking commuting routine?

The problem with my scenario is that you can't go 40 or 30 mph on your ebike if you want to get at least 500 cycles. According to Dak77 it's not possible to get 500 cycles with a daily commuting ebike routine using say, 3450mAh 5A LG Chem M36 cells or any other 18650 cell pack (eg. 8P14S) ... unless you're only going 25mph with a fair amount of pedaling and even then 500 charge/discharge cycles may be pushing it according to Dak77 ??

 

[eMark]

What I wanted to tell you is that Samsung 30Q cells develop heavy self discharging. Not all cells, but some of them and you can't tell which. Maybe other 30Q batches work better, I don't know. It's just how it is over here with that cell.

Appreciate the head's up and even more reason to balance charge the final charge from 4 to 4.07 once a week. Also my charging and especially etriking discharging will be most considerate (as if it was a 10A or even 5A cell) ... no excessive throttle if i can help it. The 50 that i just received yesterday from IMR are marked "141" not the usual "136" that you see on 30Q youtube bench tests. Do you know if "141" is an indication where they were manufactured (e.g. Samsung's China plant, Malaysia or South Korean plant), maybe "141" is a cell improvement over the self discharging problem with the "136" cells ?