a stack of 18650s

(you probably already know) but this is common in a lot of battery packs. Batteries for power tools are good sources for the 18650s too. I never checked but I saw someone open a Tesla car battery and they look like a bunch of 18650s inside too.

I refurbish my power tool batteries instead of buying new ones because it is so easy.

If he didn’t have an unfiltered public forum, people would probably still think that he is some eccentric genius.