CR2032

Lithium coin cells descend from work Panasonic (then Matsushita Electric) began in the early 1970s, when it became one of the first companies to mass-produce lithium primary batteries for consumer electronics. The lithium manganese dioxide chemistry used in the CR2032 offers a notably flat voltage output and a very low self-discharge rate, which is why a CR2032 can sit unused inside a device for years and still hold most of its original charge.

That shelf-stability, combined with a 3.0V output roughly double what a single alkaline cell provides, made the CR2032 the default choice once electronics needed a small, long-lasting power source that didn't require the mercury-based chemistries used in earlier button cells.

The CR2032 inside a desktop or laptop motherboard powers the CMOS chip that stores BIOS/UEFI settings and keeps the system clock running when the machine is unplugged. Without that trickle of power, a computer would forget its hardware configuration and reset its clock to a default time every time it lost mains power.

The same combination of small size, 3V output, and multi-year shelf life also explains its popularity in car key fobs and Bluetooth trackers like Apple AirTags -- devices that need to work reliably for a long time on a single charge but draw very little current between uses.