Fast Charge - A high rate charge — typically above 20 amps — for one to five hours that provides a quick blast of energy. It is often used to get the battery to a recharge level that can restart a vehicle. Repeated fast charges overcharge the battery and reduce service life.

Float Charge - A low, constant-current or constant-voltage charge that compensates for the self-discharge of a battery normally used in a standby application.

Flooded Battery - A type of liquid, lead-acid battery. See Vented Battery.

Frequency - The number of times that a periodic function, such as current or voltage, repeats the same sequence of values within a unit of time. It is measured in hertz.

Fuse - A safety device in a circuit that melts "open" at a specific level of current in order to protect the circuit from shorts circuits and current surges.

Fusible Link - A type of fuse in a circuit consisting of a reduced number of strands of wire held together by solder.