VTC6 Voltage loss-"is it Normal"?

I have made posts about this. Thought I may have had a thread about it and did not. So I am starting this after I could not specifically find others who have!

I will start with this graph by MOOCH from last June. My experience seems to parallel the graph, although I still need to do an updated Capacity test.




Here are 2 X VTC6 that I bought on 8.22.2016. BOTH cells have 100 cycles.

Actually that is a bit high because these cells are NOT 100% cycles. The batteries are only discharged to ~ 3.80V.Used for 15 minutes each in my M2Xvn.

So this is OFF THE CHARGER VOLTAGE/1 Hour later and then every day for Four[4] days

CELL #1 *************************CELL#2

Off the charger=4.20V***** ********Off the charger=4.22V
1 HOUR later=4.16V* **************1 Hour later=4.17V
1 Day later=4.14V *****************1 Day later=4.145V
2 Days later =4.13V**************** 2 Days later=4.14V
3 Days later=4.125V**************** 3 Days later =4.13V
4 Days later =4.12V ****************4 Days later=4.13V

That is 0.08V loss in 4 days for CELL #1 and 0.09V loss in 4 days for cell #2. The VTC6 has MORE voltage loss When I compare them to other cells the same age and older.

Example 2 X Vappower IMR 26650 that are the same age, charged to the same voltage on the same charger[ARE-C2] have resting voltages of at least 4.18V[Usually 4.19/4.20V] after 4 or 5 days.My 30Q that also are the same age NEVER have a resting voltage lower than 4.17 after 4 days or so.

I know 0.04V/0.05V is minimal in terms of run time. On the other hand[more time will tell] I definitely feel that my experience w/ VTC6 parallels "MOOCH'S" even though they have not been through that vigorous test that he did.

Brand new cell #1 was 3006mAh. Cell #2 was ​3022mAh. Both discharged @ 1Amp.HKJ @ 1Amp=2978mAh.

I will have to follow this up with a another CAPACITY test on my OPUS. That will determine a bit more. I will post that in the next few days when I get the results.


I admit I am obsessed with numbers! At this point, strictly by Voltage loss, I feel that they are degrading a bit faster than the aforementioned cells above[V'Power/30Q]

TIME IS YOURS...............

I don't think you can tell much about cell degradation by that initial voltage drop, and I'm not aware of a reason to be concerned about it varying between different types of batteries. I was under the impression 0.05-0.1V change in voltage as the cell rests after charging is normal.

What comparison are you making to Mooch's data? You seem to be looking just at rest voltage. The chart you show of his is capacity when new and after 50 fairly hard cycles (100% DoD, 5C discharge and greater than 1C charge, with minimal cooldown period, resulting in very high cell temperatures).

I do see the cells that in his test saw the greatest capacity loss are also VTC6's, which you also observed have the largest resting voltage drop. I'm not sure those are more than coincidental, although if the magnitude of resting voltage drop increases with use, that could be a hint that it is related to cell degradation.

There are many variables, I remember my battery guy Norb telling me why he would not stock the vtc6 cells when available. They are all graded, temp stored at and stored for how long(sure other factors ). As the ones available at the time were grade B, he would not buy them. Since then he does stock and sell the vtc6 under his own label. Not sure of the exact time after the vtc6 were released, but hazard a guess at 6 months later or so. So I am saying it's quite possible there are different grade vtc6 out there,some good, some average and maybe some not so good!

I AGREE that you can not tell about DEGRADATION by voltage drop alone. Loss of run time in association with output is an indication. I have noticed that. Please understand I use these lights every night with my hikes. I know the batteries, the cells and what the output should be when I am ready for a battery change.

This verifies what I suspected. Here is the capacity test.In LESS than 15 months, look how much capacity the VTC6 lost! My Opus has been with in 3 % of HKJ'S numbers. Most times well under that.

Cell # 1 went from 3006mAh to 2664mAh!!!! That is a 11.4% decrease in less than 15 months!

Cell #2 went from 3022mAh to 2731mAh. That is a ​10% decrease in capacity in less than 15 months!



On the other hand look at my VTC5 which I got on 6.7.2015 and was Born On 4.5.2015. 170 cycles and almost 2.5 years old.

I did not have the Opus 2.5 years ago. A close estimate of its capacity at 1Amp by HKJ is 2575mAh.

THIS TEST WAS DONE ON SEPTEMBER 26,2017.





None of this is perfect or 100 % accurate. However, there is No doubt in my mind what I just posted show the VTC6[at least the ones I have] degrading at a faster rate than my VTC5 and many other batteries that I have.

By the way. That LGHG2 is another battery I will not buy anymore. A much older VTC5 had more capacity! That LG got very hot while charging. I recycled it and it was only 16 months old!

For high drains I will stick to 30Q and VTC5A. Both of which still need time to prove themselves. So far, so good.

Another thing to note: When I test batteries I always test them in the common slots to make sure one particular slot is not way off. I did that with the LGHG2/VTC5. I did not need to do it for the VTC6 because they were tested initially in the exact same slots.

Interesting stuff, thanks for sharing. I have noticed a decent resting voltage drop on my VTC5's which are fairly old, but they have been performing just fine so that's good.

Another thing I've noticed on them is sometimes I'll find a few small brown marks on the outside of the VTC5's. I was a bit worried at first but they seem fine, and it seems to happen to all of them. I also was able to rub some of it off at one point when I tried, so I think it's probably coming from a light tube instead of the battery itself haha. Anyway, mine have been nice and reliable still with no strange temperatures when charging or anything like that.

Thanks for sharing the capacity test. That is useful information. We just don't know whether it correlates to the resting voltage trend without comparing the resting voltage of cells when new vs used.

I wanted to clarify - both these batteries are being swapped in and out of your light, used mainly on max mode, and on average being replaced at a little over half charge?

Do you then charge them right away after swapping batteries, or wait until it's about time to swap batteries again? I ask because as I'm sure you know, state of charge affects degradation over time. Here's a source that saw 2-3% degradation over 10 months at 50% SoC (storage only, no cycling), but about 6% degradation at 100% SoC for NMC cells.
http://jes.ecsdl.org/content/163/9/A1872.full.pdf+html

I'm in the camp that would consider that little enough to typically ignore for the sake of convenience using the light as much as you are, but it does indeed look like the VTC6 isn't quite as robust as the 30Q.

Also just out of curiosity, do you log your charge cycles, such as in a spreadsheet, or are these just estimates? I've thought about starting to do this, but I probably wouldn't actually do much with the data myself.

^^^

The only thing that matters is the capacity. I have found that as these resting voltages continue to lower, so does the capacity. HKJ has a thread/chart about that. I will try to locate it later.

Yes, I log my charge cycles and also document[most also by photo] my capacity tests on Microsoft word.

ALL these batteries are treated the same. These single cell high drains are NEVER below 3.75V ,,,excluding capacity test on the OPUS.

I am on the trail when so I can't charge them until I get home about 30 minutes to an hour depending on which cell is used first.

I walk my Husky 7.44 miles a day.more than half that at night. that is why I use and know my lights so well.

blah9 said:

Interesting stuff, thanks for sharing. I have noticed a decent resting voltage drop on my VTC5's which are fairly old, but they have been performing just fine so that's good.

Another thing I've noticed on them is sometimes I'll find a few small brown marks on the outside of the VTC5's. I was a bit worried at first but they seem fine, and it seems to happen to all of them. I also was able to rub some of it off at one point when I tried, so I think it's probably coming from a light tube instead of the battery itself haha. Anyway, mine have been nice and reliable still with no strange temperatures when charging or anything like that.

Click to expand...

You had me worried about that brown stuff on your VTC5!! Never heard of that before,,,maybe time to clean the inside of your light[tube]!!

Are your VTC5 older than 2.5 years old? It is easy to find out the manufacture date. The code on the battery will reveal that.

Same code for VTC5/6. For instance the last 5 digits of my VTC6 are YD28.

Y= year 2016 Z=2017
D=4th Month=April
28 day of the month
P=a lot code
YD28= April 28, 2016

This will unlock codes from several TOP manufactures


https://batterybro.com/pages/18650-date-code-lookup-tool

hover mouse over "ABOUT US" Then click Date checker code

Cool, thanks Capolini! I just checked the two I have on me (not home now) and they are both from February 2014. But yes, perhaps I have a dirty battery tube lol!!! Maybe I should take a wrapper off and rewrap one to see for sure what's going on with the brown spots.

Capolini said:

^^^

The only thing that matters is the capacity.

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That is not true! A glitch on my part. I know that internal resistance is also important. I am not a battery guru by any means. But I believe the internal resistance goes up as the battery ages. These IMR batteries all seem to have lower Internal resistance. Experts can take it from here.

blah9 said:

Cool, thanks Capolini! I just checked the two I have on me (not home now) and they are both from February 2014. But yes, perhaps I have a dirty battery tube lol!!! Maybe I should take a wrapper off and rewrap one to see for sure what's going on with the brown spots.

Click to expand...

That is promising that they are still working well. they are closing in on 4 years old.

I have Orbtronics that will be 5 years old on 12.21.2017! They have over 500 cycles on them,,probably about 75 to 80% of original capacity. Just an estimate based on capacity tests on the Opus.

Time to eat and then hit the trail,the exciting life of Capolini!

Capolini said:

These single cell high drains are NEVER below 3.75V

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That will degrade batteries for sure. Higher voltages (above around 3.8V) will accelerate ageing of li-ion batteries due to the chemical reactions within the battery. This will of course be more so the higher that the voltage is. This is the reason why 3.6V is the recommended storage voltage. However if your use case results in average battery voltage being high, and never using more than around 33% of the runtime, then is a bit of cell degradation much of an issue?

stephenk said:

That will degrade batteries for sure. Higher voltages (above around 3.8V) will accelerate ageing of li-ion batteries due to the chemical reactions within the battery. This will of course be more so the higher that the voltage is. This is the reason why 3.6V is the recommended storage voltage. However if your use case results in average battery voltage being high, and never using more than around 33% of the runtime, then is a bit of cell degradation much of an issue?

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Maybe you misunderstood. I am Not talking about storage them at 3.75 volts I'm talking about using them until they are at 3.75 volts.
How could draining a cell to 3.75 volts possibly degrade the cell more than draining it too 3.6 ,3.5 ,or 3.4 volts? I was always told it was the opposite of your theory.

stephenk said:

However if your use case results in average battery voltage being high, and never using more than around 33% of the runtime, then is a bit of cell degradation much of an issue?

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No disrespect, I agree to disagree with your logic/justification.

Why would anyone want a battery that degrades quicker than its competitor?? A more expensive one at that!

The cell[VTC6] will not be as useful and its diminished longevity[capacity] is a negative and a deterrent for future considerations.


I would be willing to bet that if your starting voltage for these batteries were 4.17v to 4.20v they would yield more output than ones with a starting voltage of 4.12/13v.

It does not matter that I am using them for 15 to 20 minutes until ~ 3.80V. During that time period it will have more output than a cell starting at a lower voltage. Even if it is unnoticeable by eye.

In addition, sometimes I forget my second cell. Then I have to run this light for 25 to 30 minutes. Additional capacity in this case is essential. imperative and makes CAPO happy!

Capolini said:

Maybe you misunderstood. I am Not talking about storage them at 3.75 volts I'm talking about using them until they are at 3.75 volts.
How could draining a cell to 3.75 volts possibly degrade the cell more than draining it too 3.6 ,3.5 ,or 3.4 volts? I was always told it was the opposite of your theory.

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Probably what is meant is that if you are going to do limited-depth (vs. full) discharges, then studies show that the worst degradation occurs when you do it as the highest voltages. For example, suppose that you are doing only 50% depth discharges. Then you will get better life if you center that range around 50%, i.e. use the range 20-75% capacity. Next best is at lowest possible voltages, i.e. 0-50% capacity. Worst is using 50-100% capacity range. Generally the more time the cell spends away from 50% capacity, the more degradation that occurs, because extreme voltages (and temps) accelerate parasitic degradation processes.

Look at MOOCH'S numbers with the VTC6. Mine and his are eerily similar in both starting capacity and capacity loss. Although his was basically a torture test in a short time period and mine was conducted over 15 months.

VTC6

MOOCH-Starting capacity=3011mAh. After 50 cycles=2653mAh, Capacity loss=11.9%


Mine both 100 Cycles

Cell #1 went from 3006mAh to 2664mAh! That is 11.4% decrease in capacity in less than 15 months!

Cell #2 went from 3022mAh to 2731mAh. That is a ​10% decrease in capacity in less than 15 months!

Gauss163 said:

Probably what is meant is that if you are going to do limited-depth (vs. full) discharges, then studies show that the worst degradation occurs when you do it as the highest voltages. For example, suppose that you are doing only 50% depth discharges. Then you will get better life if you center that range around 50%, i.e. use the range 20-75% capacity. Next best is at lowest possible voltages, i.e. 0-50% capacity. Worst is using 50-100% capacity range. Generally the more time the cell spends away from 50% capacity, the more degradation that occurs, because extreme voltages (and temps) accelerate parasitic degradation processes.

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This is what I've thought the wisdom was- that voltage extremes and heat extremes degrade LiIon lifecycle, so for maximum lifecycle, we'd want to keep % somewhere between 40 and 70 or so, with occasional deep discharges. If we care about maximum lifecycle. Everything is a trade-off.

I wonder how the VTC6's would have held up had they been charged to say 95% capacity instead of 100%? Perhaps much better. They do seem like awesome cells for high drain applications, according to HKJ's comparator. And I wonder how much stock we can put in Mooch's numbers, discharging cells to 2.5V 50 times in row with just 60 seconds rest in between, that does not sound like real world usage

Capollini, I'd be interested in seeing the discharge curves for your VT6's if you had an analyzer with PC connection. If the voltages stay high, then I wouldn't care hugely about -10% capacity loss after 100 cycles. Also, I think the precision on the Opus is really only +-3% at very best. IR readings seem to fluctuate more like +-10%. We can't expect it to give lab equipment results. Would I think require at least a CBA and perhaps a setup like HKJ's, and a lot of time, to get actionable data.

I was just reading a blog post about how even the cell manufacturers have a devilishly difficult time estimating real-world-use lifecycle. Mentions that LiIon expert Jeff Dahn who was hired by Tesla.

As for cell quality/ B's... I wonder how the quality of our third party cells would compare to cells directly obtained from Samsung/Sony/LG/Sanyo-Panasonic?

I returned some ebay button top 30Q's recently... the weight, length, capacity, and printed codes all matched spec... but IR was high (130-270 on OPUS), and more importantly they failed to produce turbo modes in a high drain light...

But then, from a reputable source, two other types of LG/Samsung cells with added button top also had rather high IR, in the 100-160 range on the OPUS. Still trying to find out how much IR should realistically increase from addition of aftermarket button tops.

^^^^

I do not have any discharge curves.

MOOCH'S test are well respected by the Vapers who usually test these batteries to the limits.

ALL Three batteries, 30Q/HG2 and VTC6 were subjected to the SAME test and the VTC6 came in Last!

I believe MOOCH'S test because on a real use scale[My normal use] I experienced a very similar loss in capacity. That is ALL I need to know.