A battery pack consists of two or more cells and determines the power or voltage rating of a tool. A screwdriver with a two-cell pack develops 2.4 Volts, while a drill-driver with eight cells develops 9.6 Volts.
Two or more electrochemical cells electrically interconnected in an appropriate series/parallel arrangement to provide the required operating voltage and current levels. Under common usage, the term "battery" is often also applied to a single cell.
a case which contains several batteries connected in series or in a row, available to charge more energy (power) in use