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BlueMAX li-ion cells testing from Guges Mk3

#1 User is offline   aotsukisho 

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Posted 04 February 2020 - 05:01 PM

I got some BlueMAX 3200mAh testing cells in from Guges Mk3 over at Airsoft Society 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.

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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.

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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.

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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

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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.

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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.

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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.

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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.

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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.

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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.

Edit: thread on Airsoft Society is located here: https://www.airsofts...testing.160343/ I will be posting updates to the testing here first, but Guges will respond directly on the AS thread.
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#2 User is offline   aotsukisho 

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Posted 10 February 2020 - 02:09 PM

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Time has come to closely inspect one of these things

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Peeling back the shrink wrap on the outside

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Very nicely heatshrinked over the bar going to the negative pole. Even the balancing taps are heatshrunk separately

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Stripped the bottom cell entirely, we can see that these are indeed Samsung INR18650-30Q cells. 30Q model is 3000mAh capacity, strange how even this is overstated. I am going to give them the benefit of the doubt that these are genuine Samsung cells, so this is quite strange indeed.

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Soldered on a clone Deans Ultra so I can run this on my battery charger.

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Have left this fully charged for a few days, but a discharge at ~7A showed an apparent capacity of 2391mAh

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Battery resistance is shown as 103mΩ. About this below

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Relatively smooth discharge curve, with the voltage rebound after load is removed as expected.

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https://www.wolframa...C+r*3%2Bc%3D103
So, given that a 2s is reported as 80mΩ and a 3s of the same cells are reported as 103mΩ, I did a quick analysis to determine the resistance of my test platform.

Each of these Samsung cells are 23mΩ which is very good. My charger and its cabling total 34mΩ so that needs to be deducted from each reported IR.

My opinion of these cells are improved, but I cannot get around the stated capacity. I have a game coming up next weekend, so I will equip some of my guns with these and see what the charge cycles look like afterwards.
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#3 User is offline   aotsukisho 

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Posted 25 February 2020 - 10:02 AM

Guges gave me the specs for the li-ion cells as follows:

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


I had run the battery for a game or two in a longrange M4 with and M160 spring and JG high torque motor through a Gate Warfet, held up great. Not the most stressful scenario due to the stock gearing. I then did a full charge at spec (1.5A, 4.20v/cell) then discharge at spec (600mA, 2.50v/cell) in a climate controlled room set at 65°F.

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This is more like it. Looks like the capacity discrepancy was mostly due to the 3.0v/cell cutoff that is industry standard, apparently these are good to 2.5v/cell. In the real world however, not sure how much this matters as the capacity gain from further discharge was relatively minimal - we're talking 10% capacity increase with 40% lower resting voltage. I would just set low-voltage cutoff to 3.0v/cell just to be safe, you are needlessly endangering your battery with a lower voltage and the returns simply aren't worth it.

I do have issue with the claimed 3200mAh capacity, like I said before the cells themselves were never rated for that much in the first place. That being said, the 3000mAh Samsung cells appear to be doing fine, the lower temperatures (for Hawaii anyway) should have reduced apparent capacity yet they are 1.7% off which I'd say is within manufacturing and testing equipment tolerance. I am still only around ten cycles into the battery's lifespan, we shall see how well they hold up with more continued strenuous usage.
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