YouTube video uploader Kman Auto (this YouTuber happens to do brilliant Tesla-related videos) provides us with a glimpse of what's inside a Tesla Supercharger.

Unfortunately, you won't see all the internal in this video, but it's better than nothing.

As Kman Auto states:

"Attempt to see some of the goodies in a Supercharger (specifically Onalaska WI). The outside temps are 25*F, the heat being dissipated by the unit through the use of it's cooling fan is approx 65*F."