Linked from
The 18 pages that link to Battery, each with the reason it gives.
Direct currentRelated: Batteries are common sources of direct current for standalone devices.
CoulombRelated: Its delivered charge can be expressed in coulombs or ampere-hours.
Quartz clockRelated: A battery powers the oscillator and, in analog clocks, the motor.
Voltage sourceBroader topic: A battery is a common real-world voltage source.
Radio-controlled carRelated: The battery powers the motor and electronics in an electric model.
WalkmanRelated: Battery power freed Walkman playback from wall outlets.