There is an electric bell in Oxford University that has been ringing for 181 years without replacement of batteries. Batteries degrade faster or slower, but all the batteries that we use in the devices we have at home end up degrading and, therefore, reducing their capacity. We know, above all, thanks to mobile phones, which in one or two years after their first start-up begin to offer less autonomy. It’s normal, it’s pure chemistry, and it’s inherent in lithium-ion batteries.
But what if there was a battery that took years and years and years of operation and giving life to a device? It is precisely what happens with the battery of the electric bell that we can find in the Clarendom laboratory of the University of Oxford. It has been playing since 1840, which is something, but the most curious thing is that nobody knows what his drums are made of.
The Oxford electric bell, also known as the Clarendon dry cell, consists of two brass bells, one on each side , and a clapper (the piece that strikes each bell) about four millimeters in diameter. Each bell is placed under a dry cell battery that attracts the clapper. When the clapper rings the bell, the battery emits a small charge that repels the clapper , which is subsequently attracted to the other end, and so on with a frequency of two hertz.
The curious thing is that this process has been repeated over and over again throughout the last 181 years. The battery continues to work since then. It is true that the sound is inaudible (among other things, because the device is displayed inside a glass bell), but the mechanism continues to work. And what is that pile made of to make it last so long? This is the mystery: nobody knows.
The Oxford electric bell has never been disassembled, as that would instantly stop one of the longest-running scientific experiments of today. What is known is that the battery is coated with molten sulfur to protect it from moisture, but its exact composition is a mystery. In any case, there is an explanation for the fact that it continues to work: although a high voltage is needed to start the movement, the charge that is transported from one bell to another is very low.
As explained from the University of Oxford itself , it is suspected that inside the bell there could be a Zamboni pile, since there are records of other similar experiments during the time of its creation. These stacks are built by stacking paper discs coated with zinc foil on one side and manganese dioxide on the other. If so, there will come a time when the bell will stop working , either because the zinc rusts or the manganese runs out, but so far the bell has sounded more than 10 billion times.