Button batteries, also known as coin cells, are small, round, disk-shaped batteries named for their resemblance to buttons or coins. They are widely used in compact electronic devices due to their tiny size and reliable power output.  

Physical Characteristics: Button batteries range in diameter from 5 mm to 25 mm and in thickness from 1 mm to 6 mm, making them much smaller than AA or AAA batteries. They have a flat, circular shape with a positive terminal (usually a stamped metal top with a "+" sign) and a negative terminal (a metal base with a "-" sign). The casing is typically made of stainless steel to protect the internal chemicals.  

Chemistry and Voltage: Common chemistries include alkaline (LR series), silver oxide (SR series), lithium (CR series), and zinc-air (ZA series). Voltage varies by type: alkaline and silver oxide cells typically output 1.5V, lithium cells 3V or 3.6V (higher energy density), and zinc-air cells 1.4V (often used in hearing aids, activated by exposure to air).  

Applications: Their small size makes them ideal for devices with limited space, such as:  

Watches (analog and digital)  

Calculators  

Key fobs (car remotes)  

Hearing aids  

Medical devices (e.g., glucose monitors, thermometers)  

Small toys and greeting cards with sound modules  

Safety Considerations: Button batteries pose a choking hazard, especially to children and pets, as their size allows them to be swallowed. Once ingested, they can cause severe internal burns or blockages due to the electrical current and chemical leakage. Many modern button batteries include child-resistant packaging, and devices using them often have secure battery compartments (e.g., screws instead of snap-on covers).  

Rechargeable vs. Disposable: Most button batteries are disposable (primary cells), but rechargeable versions (e.g., lithium-ion coin cells) exist for devices like Bluetooth headsets, offering repeated use with a compatible charger.  

button batteries are essential for powering miniaturized electronics, balancing compactness with consistent performance, while requiring careful handling to ensure safety.

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