In this long ongoing experiment, I attempt to see just how a “no name” power bank stands up to repeated cycling. My expectations were fairly low at the outset, but it seems I’ve been proved completely wrong, as now I’m up to the 17th posting of the experiment.
Results
This posting represents a total of 850 cycles accumulated since the commencement of the experiment, or 866 cycles from when the unit was new. The previous part has a trend which suggested the capacity was indeed declining and beginning a new degradation profile which is steeper.
However, if we look at the new data, it seems this may be a little premature. While some degradation is observed, some limited “recovery” of the capacity can be seen in the later runs. It seems that the capacity is not completely recovered, but greater variations in the measured capacity could be expected because of the inaccuracy of charge/discharge termination especially when the cell internal resistance increases as it ages. Temperature variations could also play a role here.
Even after 850 cycles, it has a good fraction of its capacity remaining, although using the 80% “failure point” (80% of 3850mAh = 3080mAh), the cell is considered to have failed. It has not, as yet, “fallen off a cliff”, and the rate of degradation seems to be somewhat “graceful”.
Conclusion
The longevity of this cell has outlasted my expectations quite significantly, and I’m somewhat disappointed in not seeing more “action” in the capacity. Unfortunately, this means the experiment will continue … next posting when 900 cycles has been accrued. That being said, it seems likely that the experiment might have to be discontinued as of the next post (or the one thereafter) due to changing circumstances which would limit my ability to perform such testing …
