By Brett Smith | Updated March 24, 2022
Photo: Joerg Mikus/Hemera/Getty Images
A potato clock harnesses the natural acidity inside a potato to create a tiny electrochemical cell. The reaction occurs when a zinc anode (often a galvanized nail) is inserted into one end of the potato, while a copper cathode (commonly a penny) is placed at the opposite end. As the zinc metal loses electrons, they travel through the potato’s phosphoric‑acid electrolyte and are collected by the copper coin, generating a small but steady electric current.
To power a simple analog clock you need only: one medium‑sized potato, two pennies, two galvanized nails, and three insulated copper wires. Connect one nail to the first penny, then run a wire to the second nail and finally to the second penny. The resulting voltage—usually around 0.5 to 1 volt—can drive a low‑power clock circuit.
Although the potato battery produces only a few volts, a 2013 study from the Hebrew University of Jerusalem demonstrated that with multiple cells and proper design it could supply enough power to charge a cell phone or laptop. This breakthrough shows that humble ingredients can, under the right conditions, support more demanding electronic devices.
