Looking through the comparator, it seems the closest “Major Brand” cell to this is the Samsung INR18650-20Q. It seems they are almost, but not quite, identical chemistry inside. The discharge curves at 5A, 10A, and 20A are almost identical. The 20Q doesn’t voltage sag as much at the beginning of the curve, but drops off a bit earlier at the end (lower capacity, even though they’re rated the same). The comparator doesn’t have a discharge curve for the 20Q at 30A, but the Parkside cell didn’t do well with that test.
Pentalobe/pentaleg tops, could these be Shenzhen BAK made?
Henrik, I think the calculated internal resistance figure in your charts needs a fix. “Cold” or barely warm cell DC internal resistance can be inferred from the discharge curve graphs. An easy algorithm could be “at ⅛ capacity figure value x-axis position read V(IREF) and V(IMAX) voltage values, then work out Rcell = (V(IREF) − V(IMAX)) / (IMAX − IREF)), whereas IMAX is the maximum current at which the cell succesfully completed discharge without issues or overheating and IREF could be the closest amperage value for which a measured discharge curve exists at ≈¼ of IMAX. In this particular case (values taken at 250mAh point):
It is automatic calculated by my test equipment during the “Protection test”, I do not really want to redo this.
Because I calculate it at a fairly high load with unprotected cells, some cells will give a rather high value.