Lighting Fires With Lemons

We all know that you can stick copper and zinc in an acid and make a battery. And the classic demonstration of this is with a lemon. YouTuber [NorthSurvival] takes this to an extreme — starting a fire by shorting his lemon battery across some steel wool. (Video embedded below.)

Now calling this a “survival tip” is pushing it. A lot. When’s the last time you went camping with a bunch of zinc and copper nails, much less a supply of fresh lemons? It might be easier to put some matches in a waterproof canister, or just bring a lighter. But when the zombie apocalypse comes, and all the lighters are used up, the man with a lemon tree will be a millionaire.

Seriously, though, this demo made us question a few assumptions. First, when people do the potato- or lemon-battery experiment, they often use multiple lemons. Why? Hooking the pins up like [NorthSurvival] did in series seems like a no-brainer after the fact.

And the lemon seems to be putting out a fair amount of juice (Amperes, that is). We’ve got to wonder — what is the short-circuit current of a lemon battery? And why haven’t we seen specs anywhere? What kind of “science education” experiment is this anyway, without measurements?

So we’re going to find some copper and zinc, and measure the current ourselves. And maybe parallel some lemons up if need be. How many lemons will it take to build a spot-welder?

[Editor’s (totally redfaced) Note: So we called for measurements, and people came up with them in the comments. The current coming out of a lemon battery is milliampy, which means that this video is a fake. Sharing the electrolyte, unless there’s more structure in the lemon than we know, should short-circuit it rather than produce more voltage, certainly at any useful current level. It’s a hoax, and we got hoaxed.]

64 thoughts on “Lighting Fires With Lemons

  1. Ferrocerium every time. Matches get wet and fall apart. Lighters can smash. Ferrocerium, you can dunk it in water, take it out, scrape it with metal and it shoots off sparks at about 3,000 °C (5,430 °F).

    1. If you are going to wire them in parallel, you CAN use a singe lemon. Put a row of cathodes and anodes as shown, but connect all anodes and all cathodes instead of shorting between anodes and cathodes. Basically, the larger the total anode and cathode surface area, the higher the current.

  2. Fake. Dude hid another battery inside the lemon.

    The current from a lemon battery is incredibly small. Nowhere even close to enough to cause a wire to heat up lime that.
    The individual cells aren’t isolated.

    Come on hackaday. You should know better.

      1. You can ignite steel wool with 9V battery, but such battery can provide few hundred milliamps, lemon battery can provide about one milliamp. That’s the huge difference.

        1. OK my bad, I never looked at the power output from a lemon battery before. 0.9 – 1.0 volts, maximum current about 1 mA if the electrodes are very close to each other. Could probably be increased a bit by making the plate size a much larger area. But not enough.

    1. Definitely my first thought too.

      I did this recently when putting the parts together for a teacher friend, and discovered even lighting an LED enough that you can see it in daylight is trickier than I expected. I had about that many electrodes and you needed to turn the lights off to see anything.

      I’d love to be wrong though, as surprise is the spice of life!

      1. I used four lemons in series and it can barely lit small red LED. So I seriously doubt he can ignite steel wool with such current. BTW, he’s doing it wrong anyways, sharing same electrolyte and connecting such “batteries” in series won’t work.

        1. Interestingly, the biology of the lemon suggests the electrolyte doesn’t have to be shared. Inside each section of lemon there are lots of individual little cells that contain the juice/electrolyte. If you did it right, you could convert each biological cell into a battery cell and chain up a much larger current. That said, I’m kinda doubting this was done since the nails are far too large to be taking advantage of the biological cells.

          Now, if the nails in the video were obviously piercing different sections of the lemon… There is room for experimentation here.

        2. The juice is contained inside the little sacs and not free flowing inside a lemon. So if he managed to poke very carefully, the juice are localized at the area around a pair of electrodes and no electric connection to the others.

          Now getting enough current to light up the steel wool is a totally different matter. Probably far better off with cells in parallel than in series to match the impedance of the battery to steel wool for maximum power transfer.

          1. To avoid some of the biology, you could just squeeze the lemon and pour it into some kind of container, preferably a metal container that can be used as anode or cathode.

    2. super fake those clips aren’t even (pure) copper they are usually made of brass or brass plated which would almost certainly make the battery even worse or non funtioning

      1. Doesn’t matter. Copper and zinc are the “usual suspects” for anode and cathode, but ANY two different metals in any acid will produce current.

        If a battery works by creating a flow of electrons between anode and cathode, why would you require closed cells? Multiple anodes, multiple cathodes, common pool of electolyte should still give multiple flows of electrons, i.e. multiple “cells,” right?

        1. Two electrodes in a pool of electrolyte gives you a battery. Two electrodes in a pool of electrolyte with a copper wire bridging them gives you a shorted-out battery.

          The configuration in the image is just a bunch of shorted-out “cells”. Only those unconnected ones at the ends actually have any potential across them, and it’s not going to be much because, for one, it’s a lemon, and, two, they’re so far apart that they’re going to maintain voltage under load even more poorly than the usual lemon battery.

    1. Nm didn’t have to gag myself just watched the end of the video and the patreon begging did it for me.

      From wikipedia:

      By multiplying the average current of a lemon (0.001A/ 1mA) by the average (lowest) voltage (potential difference) of a lemon (0.7V) we can conclude that it would take more than 6 million lemons to give us the power of an average 4320W car battery. I am with JJ no way one lemon did this.

  3. I knew something smelled fishy (lemony?). As it happens, he is demonstrating cathodic protection, where the galvanized nails will slow corrosion of the brass push pins.

    I’d love to see another video showing how many lemon batteries you would need to get this system actually going.

    BTW an easier way to debunk this “Northern Survival” video is to try to find lemons in the North!

  4. Ugh, while the lemon battery has been one of the more appealing science demos, it’s also one of the most misleading ones. It makes it easy for people to conclude that the lemon is somehow the source of “juice” (as in energy), resulting in misguided comments like “the man with a lemon tree will be a millionaire” or conclusions like the one examined here, where you can somehow stick multiple arbitrary electrodes in a single electrolyte and expect them to create a bunch of series cells.

    The lemon is a damn electrolyte. You could use seawater. You could use an orange. You could use a pot of chicken soup. Doesn’t matter. Those liquid demonstrations make it far more obvious to a student that the electrodes, rather than the arbitrary liquid solution with ions in it, is critical to operation and that adding more electrodes in the same pool probably doesn’t make any sense. The critical components of the battery are the two dissimilar metal electrodes. If modern manufacturing fails us we will still be without pure copper and zinc, so you’re better off using lemons for cooking than for batteries (not to mention it’s a bigger waste of energy to be using lemons than just getting some salt water in most areas)

    Come to think of it, that lemon farmer may actually become a millionaire during the zombie apocolypse. This silly elementary school experiment already did all the advertising – pretty much everyone knows you can make a battery with a lemon.

  5. This is completely fake. You’d be lucky to get a single mA from a lemon let alone enough to start a fire.

    We use 9v batteries for this and probably get our selves 4.5W

    A lemon would not cut it.

  6. Right, this can’t work. If there was no current path inside the lemon (because, say, the juice being contained in juice vesicles prevented two distant points from being electrically connected) then a normal, two-nail lemon battery wouldn’t work, either (it would be like putting a zinc nail into one lemon and a copper nail into another lemon). Since we know a normal lemon battery works, then there’s a current path inside the lemon. So the electrolyte is shared and you can’t connect terminals in series to add the voltages. You could connect it in parallel to allow for a higher current if you had the voltage to push it, but that’s not the way this is wired up (all the anodes and cathodes would be wired together for that, not anodes connected to cathodes).

  7. Lighting Fires with SCAMS

    I seem to remember first time I saw link to this scam it was accompanied with matching scam kickstarter campaign from same person. Not to mention patreon link.

    Another kipkay 100 batteries in one bigger battery/blind security cameras with this 10mw IR led garbage …

          1. What makes you say that? The video has ads on it, the video creator gets money from that (you can elect to “monetize” your YouTube videos). Additionally, there’s a Patreon link in the description. If you don’t know what Patreon is, it’s a service that lets creators accept monetary donations from viewers.

          2. The person that would donate to such a thing would be rather ignorant. If the lack of background knowledge or intelligence leads a person to donate to such a cause it would be considered “duped” or “fooled”, not scammed. Because no product or service is being promised for that donation, it would not be considered a scam.

  8. Although Hackaday doesn’t have the best writers, a very knowledgeable community, or helpful content… I can always appreciate the original and/or carefully vetted content.

  9. Something tells me Elliott has had enough of the snarky, vitriolic ego-tripping that a contributor on HaD can expect in the comments these days and this post is more than just just a prank. Psychological experiment, perhaps? There’s ample hints in his post that would suggest he knows this video is a hoax. You’re taking the bait. 4chan is leaking.

  10. Total bogus. and you can see it in the video as well. when he does the actual ligthing, suddenly there is a close up in which you dont see where the wires are going anymore and when he lets go after the fire is ignited, you see the wires disappear behind the lemon, then on zoom out they are attached to the lemon again

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