Soaking an onion in an energy drink to charge your iPod? It is either so bonkers it must be true or it's a YouTube hoax. First a video circulated on the internet (tinyurl.com/yqolvz) claimed to show a discovery that could revolutionise holiday packing (Darling? I can't find the damn onion!). Now it has been reported that a supermarket shelf-stacker from Portsmouth is successfully charging his MP3 player for up to an hour in this way.
Following the video's instructions, I bought a large onion, skewered it with holes and soaked it in Powerade. I vaguely remember those school science experiments where you stuck a zinc nail and a copper coin in a lemon and generated a modest electric current. This time, however, the smell of onion blended with berry and tropical fruit flavoured isotonic sports drink was enough to make me retch. And the iPod resolutely refused to shudder with energy.
"The science behind the idea isn't bad - you can generate an electric current from vegetables - but the video is a hoax," says Jon Edwards of the Royal Society of Chemistry. He explains that it can't work because you need two electrodes - the zinc nail and copper coin in the lemon experiment - to provide a reaction and a reason for an electric current to flow.
Scientists from Cambridge University have undertaken a proper version of this experiment using zinc and copper nails and a fruitbowl's-worth of apples and oranges (tinyurl.com/5nydqn). But even after cutting down the iPod's USB cable and building a cumbersome-looking cell they failed to generate enough of a charge. With a van-load of fruit and nails, they probably could but, as Charles Tracy from the Institute of Physics points out, recharging your iPod with a solar cell would be a far greener option.
