Hi,
the other day a friend of mine asked me if i could figure out why his bluetooth speaker was crackling and sometimes suddenly shutting itself down like there was no power.
I immediately checked the battery (LiPo, 3.7v) and indeed, it could not hold charge for a decent amount of time: when connected to a load ( in my case a 3.5v little incandescent bulb ), the voltage drops from 3.7 nominal to 2-ish in a minute or so. When disconnected, the open circuit voltage returns to 3.7 V.
The 2 volts were enough to still power the little bulb, until after some minutes, the bulb started turning on and off at a stable frequency, with a period of like a second, the voltage was switching between 2 and 0 volts (checked with oscilloscope).
I recorded a brief video of the phenomenon :
https://imgur.com/a/yOqExz9With time, the frequency began to slowly drop, as well as the voltage and so the light intensity, as someone would expect.
I'm really curious, I have just a basic knowledge of the working principle of a Lithium Ion Battery, but I can't figure out why this happens. Is this a normal behavior of dying LiPo batteries? And why it happens?