Fast charge - Charging in less than one hour at about 1.0C rate. Needs special charger.
Float charge - An arrangement in which the battery and the load are permanently connected in parallel across the DC charging source, so that the battery will supply power to the load if the charger fails. Compensates for the self-discharge of the battery.
Float life - The expected lifetime in hours of a battery when used in a float charge application. See also Cycle life above.
Flooded Lead Acid cell - In “flooded” batteries, the oxygen created at the positive electrode is released from the cell and vented into the atmosphere. Similarly, the hydrogen created at the negative electrode is also vented into the atmosphere. This can cause an explosive atmosphere in an unventilated battery room. Furthermore the venting of the gasses causes a net loss of water from the cell. This lost water needs to be periodically replaced. Flooded batteries must be vented to prevent excess pressure from the build up of these gasses. See also Sealed Lead Acid (SLA) Cells which overcome these problems.
Flywheel battery - A flywheel stores kinetic energy in a high speed (up to 100,000 rpm) rotating cylinder and is “charged” and “discharged” via an integral motor/generator. High power availability but low capacity.