 A secondary cell, commonly referred to as a "rechargeable battery", is an electrochemical cell that can be run as both a galvanic cell and as an electrolytic cell.This is used as a convenient way to store electricity, when current flows one way the levels of one or more chemicals build up (charging), while it is discharging they reduce and the resulting electromotive force can do work.A "fuel cell" is an electrochemical cell that converts the chemical energy from a fuel into electricity through an electrochemical reaction of hydrogen fuel with oxygen or another oxidizing agent.