<p>as for why, there are smart people in the replies who delved into the details, but to summarise:</p><p>- there *are* electrochemical, thermal, and piezoelectric behaviours in each cell, and they do contribute to noise, but you probably can't see that in this trace because it's very small and mostly low frequency.</p><p>- PP3 batteries are constructed of six cells in series. that loop of cells forms an antenna, and the noise here is mostly inductive pickup.</p>
