It's part of the whole life cycle of the battery. Just about 5-6 months ago, I still had my original Joye eGo batts from the first batch that I bought ages ago. The cycles had become shorter and shorter and I noticed - oddly I thought at first - that as the batt would lose it's charge, the led would fade at the end of the charge. I'd never seen that before. I lost 1 eGo, 2 Rivas and some other knockoffs on shorts from bad
coils.... so I never saw the 'old age eGo' where it finally died of natural causes
And as I went on, the fading led batt finally died and then the others started with the fading led thing and also eventually died. I only have two of the originals left now and have replaced all with Joye eGo-c 'upgrade' batts.
It was probably in the last three months where I began to notice the shorter charge/use cycle and only in the last month where the led started to fade at the end of a charge.
I might point out that I split up my
vaping by 5 or 6 different batts and flavors, so my batteries tend to last longer than some others who are power
vaping one favorite flavor most of the time.