Inside a 9-volt battery

This guy hacked a 9–volt battery in order to make a AAA battery that he needed.

With a needlenose pliers, gently peel away the metal cover of the 9 volt battery. It should separate along the seam without much effort...

I remember thinking at one point that a 9 volt battery was just a small box full of acid or something, but as you can clearly see, it is just constructed of six smaller 1.5 volt cells wired in series.

How to hack a 9–volt battery into AAA batteries