Tutoring chemistry, the distinction between cell and battery is noted.
In electrochemistry, a cell is a single unit of electrical energy production. A cell comprises an anode and cathode, plus the ingredients and the environment needed for the chemical reaction that outputs electrical energy.
A battery comprises more than one cell connected so that they work together to deliver energy to a circuit.
People have come to refer to single cells as batteries. I’d say that the button-style power sources found in calculators, watches, etc are cells. If a calculator contains two of them, those two cells constitute a battery.
The typical car battery really is one, since it contains six cells connected.
Mortimer, Charles E. Chemistry, sixth ed. Belmont: Wadsworth, 1986.
Giancoli, Douglas C. Physics, fifth ed. New Jersey: Prentice Hall, 1998.
Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.