A Flow Battery is a form of secondary battery in which the electrolytes are not confined to within the power cell it's self. Additional elecrolyte is stored in tanks which is then circulated through the cell ( or cells ) by a pump. Flow batteries are distinguished from Fuel Cells by the fact that the chemical reaction involved is reversable and so they can be recharged without replacing the electrolyte. A secondary cell is any kind of cell in which the electrochemical reaction of interest is reversible. ... An electrolyte is a substance which dissociates free ions when dissolved (or molten), to produce an electrically conductive medium. ... An electrochemical cell is a setup used for creating an electromotive force(voltage) in a conductor separating two reactions. ... A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ...

Examples of flow batteries include the Vanadium Redox Flow Battery and the Hydrogen Bromine Flow Battery