The endurance test for this power bank started back here, with the last update providing the data for the first 50 test runs (total of 66 cycles since new). Now, another 50 cycles have been completed, for a total of 116 cycles from new. For a cell that’s normally expected to survive 300-500 cycles, that’s about 23.2% to 38.7% of its lifetime.
How did it fare?
It seems that the cell itself has done quite well. The rate of degradation seems to have locally “slowed” a little. The gradients themselves now imply a cycle life of 868 cycles (before, 716 cycles) to 80% of original capacity. The correlation value has mildly improved.
Observant readers will note that one data point (run number 76) has been omitted. This is because it registered an abnormally low value of 3358mA once off, likely due to a long period spent hooked up to the USB charger at full charge with its LEDs on while three Xiaomi units were tested (two real, one fake). This unit probably does not do a topping charge after fully charging.
When plotted with a scale starting from zero, the degradation as a function of the whole cell capacity can be seen to be relatively insignificant. The fact we’ve been through 116 cycles is quite a bit, and many device users may not reach this level even throughout the lifetime of the unit (especially if only used for emergencies).
The cell seems to perform very well and testing has mostly been consistent in a slow degradation trend of about 0.8868mAh per cycle. The implied cycle life exceeds the 300-500 cycle expectation at the moment, based on linear projection to 80% capacity. It’s been a lot of effort thus far to get to 116 total cycles – testing will continue if time permits to see how it continues to age.