KeepPower 16650 '2500 mAh' Cells - Initial Check

[aznsx]

I recently purchased 4 KeepPower 16650 ('2500 mAh') cells, which are my first cells in that size, and I just did my usual initial first basic checks on them to verify function / consistency, and get a general feel for the format. The market options in this size appear limited, and since I'm aware they are used by some others, I'll post the numbers I saw for anyone who might be interested in such 'actual' / empirical data.

The Net / Bottom Line: When doing quick calculations on flashlight operating times, the default / ballpark number I will be using for capacity is: ~1750 mAh. Three of the cells grouped fairly well, with the 4th being a bit of an outlier on IR / capacity. I'll label #4 'N+1' and use it last;-)

Details: The cells are new, purchased from the same supplier; the first in one order, and 2-4 in a second follow-up order. The first cell had a couple of very shallow discharge / charge cycles on it from checking function in the light I bought it for, while 2-4 had only their initial charge for this testing. They all arrived @~3.6V.

Testing (and charging) was done using a current vintage SkyRC MC3000, with one verification test w/ a second mint MC3000 to confirm consistency / CAL. Firmware Versions: 1.15. There were rest periods between all operations.

The Numbers:

Factors behind the numbers:

• The base cell for this top level assy. is reported to be: Sanyo UR16650ZTA. Although I've seen nothing which would rule it out, it's unknown whether this same base cell might be used in other top assys. with Orbtronic or Eagtac labels.
• This cell is rated at a 'Nominal Capacity' of 2500 mAh, with a 'Minimum Capacity' of 2400 mAh.
• The base cell is rated at 'Nominal Voltage' of 3.7V, 'Max Voltage' of 4.35V, and for CV charge termination of 4.35V for 'full capacity'. The safety circuit used is reported to have Over-Voltage threshold @ 4.2V, so that's the appropriate charge termination for this top level assy. 'protected' cell. Per HKJ, who tested the base cell using both termination voltages, this amounts to a capacity penalty / de-rating of ~260-280 mAh @4.20V.
• I tested these to a discharge cutoff voltage of 2.8V. The base cells are rated to 2.5V, and that's likely the value the rated capacity is based on; however to avoid possible safety circuit LV shutdown nullifying my whole test, I did not push that limit. For reference, HKJ also used 2.8V with the base cell. Clearly there is some small penalty for missing that last .3V at the end of the curve, but although I do not have a number for that, I suspect it's relatively small.
• His test result for all the same parameters I used for 4.20V charge, and 1A discharge to 2.8V was: 1907 mAh. Keep in mind that, among other factors, that safety circuit does add a modest amount of resistance (IR) to the top assy. It probably adds ~50 mΩ or so, (and you can see an example of the inverse effect of IR on capacity reflected in the results for cell #4). His testing did also confirm that the base cell performed well up to its 5 A rating. In my case it's powering a P60 module that draws </=3A @ 4V, so it'll have a bit of headroom.

My perspective: Everything is "compared to what", and priorities decide things. These should provide me with a power supply which can deliver roughly the same capacity in mAh, at the same voltage, and with roughly the same current sourcing capability as 2 of my 16340 cells connected in parallel would, but this will fit a 16mm chamber '2L' flashlight, and avoids potential downside risks of a series cell arrangement. That's the 'comparison' I'm making. That's essentially what I wanted, so I don't think I have a lot to complain about (yet;-). It would be nice to see #4 a bit closer to the others, but it's what it is, it's documented, and this is also why I always prefer to test 4 cells ;-).

Unrelated side note FYI: While I'd trashed my whole kitchen counter with stuff already and was doing other things, I decided, just for grins, to run the exact same discharge test on Cell #2 using an Opus BT-C3100 I had out, at 1A, to 2.8V. It reports: 1880 mAh, vs 1767 w/ the MC3000. I normally just use ~7% for that correlation factor, so those numbers 'sanity check'. Some who use / have used that charger (or this one) might find that interesting.

All the above info aside from my measurements is based on data / info from the following 4 sources, which I'll link here to save a few clicks for anyone wanting to see the source(s) (along w/ a link to the referenced Orbtronic cell). Thanks, as always to HKJ for the high quality info!

Please do let me know what I screwed up here / needs correction, and as my cell/batt knowledge is rather limited, thoughts / comments / additional facts are also welcome.

Cheers!

KeepPower 16650 battery lithium ion protected 16650 3.7V 2500mAh Sanyo UR16650ZTA P1665J

* Quality Protected Li-ion Rechargeable Battery * Brand: KeepPower * Size: 16650 * Part No.: P1665J * Maximum Size: (D)16.7*(L)67.9mm(±0.2mm) * Nominal Voltage: 3.7V * Nominal Capacity: 2500mAh

www.keeppower.com.cn

Sanyo ur16650zta ur16650 3.7v 2500mah high capacity li-ion battery made in Japan

* Quality Rechargeable Lithium-ion Cell UR16650ZTA * Brand: Sanyo * Model: 16650 * Nominal Voltage: 3.7V * Nominal Capacity: 2500mAh * Made in Japan

www.keeppower.com.cn

KeepPower 16650 2500ma Li-ion Protected Cell – Malkoff Devices

16650 KeepPower 2500mAh Sanyo UR16650ZTA 4.20V Protected Button Top This is a quality Japanese made cell and protection circuit. Assembled in China. This battery will fit Malkoff MDC 2CR123 bodies. It will also fit some stock Surefire bodies. PRODUCT DETAILS KeepPower 16650 2500mAh...

malkoffdevices.com

Test of Sanyo UR16650ZTA 2500mAh (Magenta)

16650 Protected Li-ion Orbtronic Rechargeable Battery - Replacement for 2x CR123A - Battery case included

16650 Battery Protected Rechargeable Li-ion Replacement for 2x CR123 2500mAh | Orbtronic 3.7V cell.

www.orbtronic.com