If you watch the video, you’ll note that the guy squeezes the lemon right at the beginning. Also, he inserts zinc nails into pre-existing holes in the lemon. Almost as if he’s done it before.
I don’t know how well it works to hook the cells in series like that, since they are all in the same lemon. I’d think there would be a lot of unwanted current pathways there to reduce his power output.
Maybe a better plan would have been to slice into the lemon to separate the cells, and put glass cover slips into the slits. Also, he could inject some copper sulfate around the copper nail holes, so that the chemistry wouldn’t depend on escaping hydrogen there.
But then, how many people keep cover slips and copper sulfate in their camping gear? Maybe not as many as have lemons and zinc and copper nails …
