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Discussion Starter · #1 · (Edited)
(Crosspost from my own forum/work log, where updates will be posted first: Li-ion cells testing (BlueMAX, Titanpower, Kypom) I will try to remember to update this thread here too)

I got some BlueMAX 3200mAh testing cells in from @Guges Mk3 to test, these will be used in some of my more demanding setups to see how they perform both stock and upgraded. I got them in a couple of weeks ago, but have been busy outside of work and not been able to test them much.


Here they are as I opened the box, nicely sleeved. I immediately wondered why they had such thin wire (18AWG?) and two of them came with mini Tamiya connectors. This will need to be corrected in the near future.


Since one of them came out of the box with knockoff Deans Ultra plugs, I could use it with my RC lipo charger. I charged the lipo up and discharged it a couple of times, this is the last result. 3A discharge target, run til 3.2v/cell.


Discharge calculations show internal battery resistance at 80mΩ which is a lot higher than I expected. Will have to re-run these tests after some real world abuse, maybe these still need to be broken in


Very linear discharge curve, which is good. There's a lot of empty time afterwards since the charger doesn't stop graphing after the charging cycle finishes lol.


Verifying individual cell voltage with my Hitec Lipo Checker, each cell is at 3.24v which is good to show that the cells are matched pretty well.


Charging the battery back up at 1.0A. This charger does not have a balance tap to check each individual cell during the charging process, so I left the Lipo Checker attached which equalizes cells automatically. Strangely enough, the reported capacity going into the battery was a lot lower than the 3200mAh advertised. It is relatively close to the 2661mAh that got discharged, so perhaps these cells are mislabeled and/or overstated capacity like most in the industry. Hmm.


Peak charge voltage was 8.401v. Still reporting the 80mΩ internal resistance, I will see if the other batteries have a similar 40mΩ/cell result.


This is the charging graph, due to the way lipos charge it's not as informative as the discharge graph. I may have left it hanging for a few minutes after the cycle finished too.


There was some post-charge balancing needing to be done, but still fairly close considering the Lipo Checker does not bleed voltage to match cells anywhere near 1A.

Interesting to see that these cells' actual capacity is around 2600mAh, which is exactly what Titan Power's 18650-based sticks are rated for. Again, they may still need a few more cycles to loosen up to their true capacity, so take this initial test with a grain of salt. I should have the rest of the results by the end of this week, after I solder on appropriate connectors (knockoff Deans Ultras) in order for my charger to use them natively.
 

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Thanks aotsukisho!

This is the detailed evaluation I needed. My rudimentary testing and changing was also throwing up a similar number for capacity, but I don't have the setup for IR.

Does this additional information help?

3.1 Standard discharge capacity Min. 2,950mAh - Charge: 0.5C(1.5A), 4.20V, 0.02C(150mA) cut-off @ RT - Discharge: 0.2C(600mA), 2.5V cut-off @ RT * 1C = 3,000mA

3.2 Rated discharge capacity Min. 2,900mAh - Charge: 4A, 4.20V, CCCV 100mA cut-off @ RT - Discharge: 10A , 2.5V cut-off @ RT

3.3 Nominal voltage 3.6V

3.4 Standard charge CCCV, 1.5A, 4.20V, 150mA cut-off

3.5 Rated charge CCCV, 4A, 4.20V, 100mA cut-off

3.6 Charging time Standard charge : 132min / 150mA cut-off (@ RT) Rated charge: 60min / 100mA cut-off (@ RT)

3.7 Max. continuous discharge 15A (@ RT)

3.8 Discharge cut-off voltage 2.5V (End of discharge)

3.9 Cycle life Capacity ≥ 1,770mAh @ after 250cycles (60% of the standard capacity @ RT) - Charge : 1.5A, 4.20V, CCCV 150mA cut-off @ RT - Discharge: 15A , 2.5V cut-off @ RT 3.10 Storage characteristics Capacity recovery(after the storage) ≥ 2,320mAh (80% of the rated capacity @ RT) - Charge : 4A, 4.20V, CCCV 100mA cut-off @ RT - Storage : 30 days (@ 60℃) - Discharge : 10A , 2.5V cut-off @ RT
 

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Discussion Starter · #3 ·
I will try to put the cells under a few heavy stress cycles and then rerun tests. I can also modify the charge/discharge cycles to try and see if it reports different capacities. I have to figure out what's wrong with my power supply (modified an older PC ATX unit) as it's cutting out at higher charging current, I think the connectors I used might have surface corrosion as it normally sits outside with my more basic lipo charger.
 

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It's supposed to be a Samsung Cell. Perhaps you may want to cut open the shrink wrap and take a peek. This is why I am very Adamant against opaque shrink wrap.
 

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Discussion Starter · #5 · (Edited)
Got to them over the weekend, and they are indeed Samsung cells.


However, the model is INR18650-30Q, 3000mAh. I hope they are genuine.


I also was able to calculate the internal resistance for my charger for a more accurate measurement of the cell itself. These Samsung cells are 23mΩ each.
 

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Spec Sheet BTTY TYpe:

3. SDI Model : INR18650-30Q
4. Approved by Division Signature Date / / / / / /
5. Date of Application (YY/MM/DD) : 2016/07/01
6. Supplier : SAMSUNG SDI Co., Ltd.

Additional from Factory of the packs.

++++++++
Hello Chris,

From the specification datasheet, the cell’s capacity is close to 3000mAh, less than 3000mAh, during winter, it’s less due to lower temperature.

Regards,


Jeffrey
++++++++
I then asked why they are listing the packs as 3200 when they are 3K cells.
 

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Discussion Starter · #7 ·

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It has been fun talking to the Factory Rep. I started questioning him about labelling and passing your data on the pack.

Then he whips the stick of experience on the time he has been in the industry and that he knows "the" market.

I sadly had to say I was at the planting of the seed that grew the tree where you got your stick from and showed a picture of the common pack configurations that "I" invented in 2002 with KAN 1050 cells. The only pack of the day was a MINI configuration 600AE NICD...funny he hasn't responded to any of my "facts"....
 

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Discussion Starter · #10 ·
I doubt he's been in the industry as long as you (or I, to a lesser extent) has if he's still comfortable lying about capacity for the sake of marketing. If that is his target audience in the "market" he is so familiar with, then that would explain the slight overstatement on capacity and the frankly unforgivable 6x inflation on C rating printed on the battery pack. It is dangerous to sell this as a 3200mAh 30C pack, as that implies it can handle 96A continuous - that is almost 4x the surge rating assuming good cooling of the battery, which is not happening when it's stuck in a crane stock or buffer tube. The smaller gauge low strand count wires do not inspire confidence in high current capability either.

This should be labeled and marketed as a 3000mAh 5C pack, period. 15A constant and 26A surge is more than enough for most mildly tuned guns, I know my NGRS came with a 10A fuse, TK.45 came with a 20A, and Combat Machines come with 25A for some reason. Avoiding marketing hype is why I supported companies like Castle Creations while doing RC as they do not even play the amp ratings game with their electronics. I'd say the battery capacity isn't even that important these days, it's all about the target amp draw...which the C rating has far bigger impact. That being said, hardly anyone it seems has the equipment nor patience to do any real testing on every single one of their motor setups so it's all guesswork anyway, even with computer ETUs that report data.
 

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I'd say internal resistance is the most relevant number as it's what most directly correlates to the actual performance of the battery. From what I've seen it can be either surprisingly high or low compared to the discharge rating some times. My 11.1V 25C 1200mAh stick li-po has almost the same internal resistance and performance as my 11.1V 75C 1050mAh brick li-po, both from Gens Ace, something that surprised me.
 
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Discussion Starter · #12 ·
I'd say internal resistance is the most relevant number as it's what most directly correlates to the actual performance of the battery. From what I've seen it can be either surprisingly high or low compared to the discharge rating some times. My 11.1V 25C 1200mAh stick li-po has almost the same internal resistance and performance as my 11.1V 75C 1050mAh brick li-po, both from Gens Ace, something that surprised me.
You're exactly right, but the general public does not know what to do with a mΩ spec - C rating correlates with internal resistance which is why in general I say it's most important, assuming it's honestly derived.

Your 75C will probably hold up better under extremely heavy amp draw, internal resistance does change based on factors like temperature and state of charge. There's also the possibility of batch outliers, or accidental mislabeling, which I'd assume happens regardless of the manufacturer. Main thing is you're happy with your purchase, and it's performing well when matched with an application within its spec.
 

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I used to gush about Team Orions ~2.5mOhm NIMH packs in 5000mah.

And the regular Airsofter would just have a blank look on their face.
 

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You're exactly right, but the general public does not know what to do with a mΩ spec - C rating correlates with internal resistance which is why in general I say it's most important, assuming it's honestly derived.

Your 75C will probably hold up better under extremely heavy amp draw, internal resistance does change based on factors like temperature and state of charge. There's also the possibility of batch outliers, or accidental mislabeling, which I'd assume happens regardless of the manufacturer. Main thing is you're happy with your purchase, and it's performing well when matched with an application within its spec.
You're exactly right, but the general public does not know what to do with a mΩ spec - C rating correlates with internal resistance which is why in general I say it's most important, assuming it's honestly derived.

Your 75C will probably hold up better under extremely heavy amp draw, internal resistance does change based on factors like temperature and state of charge. There's also the possibility of batch outliers, or accidental mislabeling, which I'd assume happens regardless of the manufacturer. Main thing is you're happy with your purchase, and it's performing well when matched with an application within its spec.
Interestingly Gens Ace found a way to up the discharge rating without decreasing the internal resistance by literally forcing the battery to not puff. What they did is to reinforce the batteries with an aluminium plate on the two largest sides and wrap them tightly in place. They found that physically preventing the li-po from puffing made it handle higher current.

It's just an interesting observation that discharge rating doesn't necessarily correlate with the actual performance of the battery.

I used to gush about Team Orions ~2.5mOhm NIMH packs in 5000mah.

And the regular Airsofter would just have a blank look on their face.
2.5 milliohm ni-mh cells? What kind of sorcery is that?
 

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Actually some were as low as 1.6 mOhms in the 5300mah. I was wondering if the only thing holding the voltage in was the structure of the battery.

This was a cell that was available in 2010. I can only find the 5100mah now...I am surmising while the IR was low...the durability was lower.
 

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I imagine those were practically disposable batteries. For RC racing it would make sense to have ni-mh batteries that deliver high performance for a low number of cycles. I guess it could be considered a "sacrificial" battery for competition use.
 

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Discussion Starter · #17 ·
Interestingly Gens Ace found a way to up the discharge rating without decreasing the internal resistance by literally forcing the battery to not puff. What they did is to reinforce the batteries with an aluminium plate on the two largest sides and wrap them tightly in place. They found that physically preventing the li-po from puffing made it handle higher current.
lmao brb turning all of my lipos into 200C with some sheet metal

Surprised that it works though, and strange - weren't their batteries were designed for aircraft use?

It's just an interesting observation that discharge rating doesn't necessarily correlate with the actual performance of the battery.
Well, when we're talking with normal unassisted battery packs the generalization holds true. My major point was just that most people don't know or care about internal resistance, they just need to know what number to look for

Actually some were as low as 1.6 mOhms in the 5300mah. I was wondering if the only thing holding the voltage in was the structure of the battery.
I have not heard of those, that is a multiple order of magnitude improvement

For RC racing it would make sense to have ni-mh batteries that deliver high performance for a low number of cycles. I guess it could be considered a "sacrificial" battery for competition use.
That is exactly what RC batteries were back in the day, and even now to a certain degree. An electric ground RC is far more stressful to a battery than an AEG...huge current dumps from zero RPM full throttle, extended periods of heavy current draw, regenerative braking flowing current back into the battery. Back in the days of NiCds you would gear as high as you can while having just barely enough temperature overhead and mAh available to finish the race, and after the heat (lol) was over, yank the battery out and dunk it in water so it would be cool enough to charge up again
 

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I don't know the exact details, but that's how they describe their "Tattu" line of li-po's.
 
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Discussion Starter · #19 ·
I don't know the exact details, but that's how they describe their "Tattu" line of li-po's.
Now that I think of it the aluminum plates may be acting as heat spreaders or heatsinks, effectively decreasing thermal resistance and allowing the battery to remain in a higher current delivery bracket.

This would have the side effect of clamping down lipo puff, but then again may delay visual evidence of battery pack degradation. A bunch of our 2016 and 2017-produced laptops at work are having their lipos enter end-of-life and swelling over the past year or so, and the way the end user finds out is their laptop chassis splits open horizontally right under the palmrest/touchpad.

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