It is true that they are not famous these 20650s, we would expect much better results on this cylindrical battery format, we can see that its internal resistance is catastrophic and that from one cell to another their capacities vary enormously.
As far as I am concerned, I acquired three Chinese-made 20650-format SZNS cells, which have similar specifications on paper to those tested by HKJ, ie: 3350mAh of typical capacity and a maximum discharge rate of 2C officially therefore 6.7 Amps maximum theoretically, but after several tests they have proved much better than indicated in their official specifications. Because I get the following results:
Measured capacities (Discharge 4.2v-> 2.5v@0.2C (670mA)):
- 01: 3465 mAh
- 02: 3476 mAh
- 03: 3445 mAh
note: their actual capacity are rather regular
Internal Resistances (measured in ACIR @ 1kHz on YR-1035)
- 01: 35.0 milliOhms
- 02: 33.4 milliOhms
- 03: 34.7 milliOhms
note: here too it is rather regular and especially not too high for a cell having officially, a maximum discharge rate of 6.7A (besides it is these results of IR that pushed me to test levels of discharges higher on these cells).
Maximum temperatures reached with a discharge rate of 4C (13.4 Amps)
(measurements with SENFU probes A10b (plated probes directly in contact with the center / middle of the metal cylinder of each cell)):
- 01: 63.2 ° C
- 02: 64.9 ° C
- 03: 62.7 ° C
note: after I did not want to test higher in discharge by fear greatly reduce their life cycles, but it’s already not bad for cells that have official specs of 6.7A maximum discharge to reach double ( 13.4A) without incident.
I put official photos this cell model SZNS 20650, because mine have wraps in sorry states (I absolutely must rewrap them ;-))
