The miniaturization of the battery began in war. Image courtesy
Eric S. Hintz. A small, hidden force in our world keeps hearts
beating and clocks ticking. Miniature batteries, or “button
cells,” inconspicuously power our watches, hearing aids, and
pacemakers. Meanwhile, standard alkaline batteries—slightly
larger and even more pervasive in the familiar AA, AAA, and
9-volt sizes—run our flash cameras, portable radios,
flashlights, and smoke detectors. We rarely see the batteries
when they’re hard at work, powering much of our modern
technological society. It’s easy to forget they started out big.
The first batteries may date to as early as the 2nd century BCE,
based on a 1936 find in Baghdad, Iraq. Workers there unearthed a
strange-looking artifact: a sealed clay vase with a protruding
iron rod surrounded by a cylindrical copper tube. When
archaeologists constructed a replica and filled the vase with an
acidlike vinegar or grape juice, the proto-battery produced two
volts of potential. The archaeologists specu