Coincell

A coin cell, also known as a button cell, is a small, round battery designed for compact electronic devices. These discs are thin and flat to fit in shallow slots in products such as watches, calculators, remote controls, memory backup modules, and handheld devices. They typically range in diameter from about 5 to 25 millimeters and in thickness from about 1 to 5 millimeters.

Chemistries vary among coin cells. Lithium-based lithium manganese dioxide cells (the CR family, for example CR2032) provide around 3 volts and high energy density. Silver oxide cells (SR family) deliver about 1.55 volts and are common in watches and small electronics. Alkaline coin cells offer roughly 1.5 volts and are used in some low-drain devices. Zinc-air cells are used primarily in hearing aids and are activated by exposure to air, which affects their performance. Rechargeable variants exist but are less common; they include some lithium-based and other chemistries used in specific applications.

Construction and performance characteristics are shaped by their form factor and chemistry. A coin cell consists of a circular metal can, a sealed top cap, an electrolyte, and a separator. The positive terminal is typically the top cap, with the can acting as the negative terminal in many designs. Capacity depends on size and chemistry; for example, a CR2032 may store on the order of 200–250 mAh at low drain, with capacity diminishing at higher discharge rates or elevated temperatures. Self-discharge is relatively low for lithium-based cells but higher for some alkaline or zinc-air types.

Uses and safety considerations are important for coin cells. They power devices requiring compact, reliable energy with long life at low current draws, such as watches, key fobs, and computer RTCs. Handling should avoid puncture, short circuits, and exposure to heat; keep out of reach of children and recycle or dispose of spent cells according to local regulations.