In a single cell battery, is voltage exactly equal to cell potential?
It is not uncommon for two identical phenomena to be described by different terminology in different contexts or scientific disciplines. In this case, voltage and electric potential difference refer to the same thing. According to this Wikipedia article:  


  Voltage, electric potential difference, electric pressure or electric tension (formally denoted ∆V or ∆U, but more often simply as V or U, for instance in the context of Ohm's or Kirchhoff's circuit laws) is the difference in electric potential energy between two points per unit electric charge. The voltage between two points is equal to the work done per unit of charge against a static electric field to move the test charge between two points. This is measured in units of volts (a joule per coulomb).