This is one of my longest running experiments – an experiment to see how well one particular power bank handles repetitive cycling, just to see how the lithium polymer cell and the electronics handle cycles. This is the 13th part – as of the last posting, we had reached 600 cycles in the experiment, or 615 cycles from new. This posting adds yet another 50 cycles to the tally.
The power bank has now reached 650 cycles since the beginning of the experiment, or 665 cycles from new. The trend of degradation seems to continue, although the variance has slightly increased. The degradation seems to have been at a slow rate prior to “pausing” the test for my PhD. After resumption, a big drop in capacity was seen, that was not recovered – this was related to storage of the unit at full charge. Since then, the rate of capacity degradation seems to have increased.
Of course, it’s still not anywhere near completely useless – the worst result still shows capacity >3100mAh which is still >80% of initial capacity (hence, not failed yet). However, the average trend without the noise looks to still have ~3250mAh or 84.4% of original capacity.
It still seems the storage had a big impact compared to cycling the cell in terms of damage to cell capacity. That being said, we have reached 130 – 217% of the expected lifetime.
Watched pot never boils … watched battery never fails. But it’s still interesting, so I’ll probably continue for another 100 cycles at least.