Yeah, but the lighter won’t save you from scurvy.
Correct. In order to make multiple cells out of one lemon, you need to isolate each pair of electrodes, i.e. slice the lemon. That way, the wires cross between slices.
The way it is shown, there is no way the series connected electrodes are contributing to the charge. With what is shown, each wired pair is a closed circuit.
So, and I think this was stated upthread, if you take the same configuration as in the photo, drop the wires (and the attempt to link in series) you could connect the in parallel and get more current (with greater metal surface area) but low voltage. You could wire up several similar lemons in series to step up the voltage.
I wonder if some distance would effectively isolate the nail pairs. Like, could you wire up nail pairs on opposite sides of a watermelon in series and get a step-up in voltage, or will the electrons “see” the nails on the other side of the melon.
Rather than try to build a battery, it would probably be easier to squeeze the juice out of the lemon then use said juice to focus the sun’s rays on some kindling.
MRE heaters use a powdered iron and magnesium alloy in salt water to create jillions of short-circuited galvanic cells that according to Wiki generate about 50 kilojoules. Having used them, I can attest they emit a strong ozone smell; any hydrogen is undetectable. It would be difficult to harness that to ignite steel wool, though.
How would additionally sugar and water affect the conduction? The lemon has some of one and a lot of the other. When life gives you lemons, then make lemonade, then fire.
Some, sure, but not very effectively. You’d need the internal resistance of the intervening fruit to be greater than the resistance of the rest of your circuit.
Maybe I’ll try it as a summer science project once kids are out of school.
OK here’s what I don’t get about the video. Why is he wiring the zinc nails to the copper brads? What purpose is that supposed to serve?
It’s supposed to create a “series” of cells to step up the voltage (voltaic pile). But others have pointed out upthread that this will not be effective (because the cells are not isolated from each other). This video is felt to be a hoax by OP (who says he tried the experiment). Other posters agree for theoretical reasons.
Still thinking of selling this idea as science project to my boy.
Does the Samsung Galaxy Note 7 qualify as a lemon yet?
After reading the comments, but before watching the video, I was wondering if the different segments of the lemon would offer any sort of isolating effect. But, the brads and nails aren’t even going in the right direction in the demo for that.
Lemon powered Supercar- WORLD’S LARGEST Lemon Battery
Nothing dinky: A beautiful Volkswagon Formula 1 [?] race car. 1,232 lemons in parallel.
With how much copper and zinc (or whatever metals they’re using)?
I watched, only half-paying attention, till I heard the lemon count. He shows the construction in detail (which I skipped), and also goes over some other home-do-it-yourself battery projects.
You should paid attention to the part where they finished the battery and actually tested how much current they were getting. Spoiler: Nowhere near enough to power the supercar. Orders of magnitude too little. They switched to those other projects as a way to try to get sufficient current to fill up that giant storage battery well before the race, which is sometime today; I’ll have to go see if I can watch it online somewhere. And I’m wondering why they just didn’t plug it into wall current. 
They made arrays of sharo metal strips and impaled hundreds of lemons on them.
They seem to have done that in an interesting way that I doubt was actually very efficient. They had long metal strips that they cut into fairly complex serrated shapes, with jagged protruding ellipses. They placed copper and zinc strips approximately a half inch apart and impaled a bunch of lemons over the protruding serrations. They had multiple strip pairs, and seem to have mounted them in series (“we wired the first half of the racks to be in parallel, and that was in series with the second half of the racks which were also all in parallel” ??). Each ~30" row of lemons is a single cell, and they had what looks like 80 rows total, so maybe this means that they ran 40 cells in parallel and ran that bank in series with another bank of 40 cells in parallel. Correct me if I’m wrong but that would make twice the voltage of a single cell and 40 times the current, right?
At any rate, the complex shapes that they cut out made for nice places to jab the lemons, but it meant that they were using only a fraction of the surface area of the metal strips for actual contact with the electrolyte of the lemons, especially since they didn’t seem to be pushing the lemons in as far as possible. From a power standpoint, they would have been better off leaving the metal strips uncut and making sandwiches of copper-lemon slices-zinc, where the lemon slices were tiled as densely as possible over the metal surface.
I will grant that their technique was more photogenic and probably took a lot less time to install the lemons than making sandwiches would have.