This is one of those ongoing experiments which just seems to keep dragging on and on. Initially, I thought I’d torture a relatively unknown power bank by cycling it over and over on the test rig, expecting to see it fail not too far past 500 cycles. Now, I really don’t know who’s being tortured, since it’s now reached 950 cycles since the experiment started, or 966 cycles since manufacture.
This time around, the results do have something interesting to show. From the last result, it seems that the degradation took a good dive for a number of cycles, before recovering towards the accelerating degradation trend established earlier. The reason for this dive may be related to early charging termination, as the recovery may have had to do with the charging being interrupted after a full charge to do another top-up. But the fact the battery capacity didn’t recover further than about 2560mAh tells us that the cell capacity is really diminishing on a cycle by cycle basis, and is accelerating. The narrower range of the data with less spikes seems to reflect the fact I now hold my room at a fairly well-regulated 21 degrees due to other temperature-sensitive testing which is also going on at this time.
In the grand scheme of things, the degradation is becoming more noticeable. Only 65% of the initial capacity remains, however, this is still a useful amount (2500mAh).
It seems some strange reversal of degradation occurred in this set of data which may have been charging circuitry related, but otherwise, the degradation almost appears to be accelerating. Around 2500mAh remains, which is about 65% of initial capacity and still somewhat serviceable.
Unfortunately, due to changes in circumstances in the near future, it seems I won’t be able to continue this experiment much longer, so the next report at cycle 1000 (or 1016) might have to mark the end of the experiment, just when things start to get interesting.