How does a secondary cells are connected in a battery to increase the terminal voltage?

To increase the terminal voltage of a battery, secondary cells (rechargeable batteries) are connected in series. In a series configuration, the positive terminal of one cell connects to the negative terminal of the next, allowing the voltages to add together. For example, if two cells each have a voltage of 3.7 volts, their combined voltage in series would be 7.4 volts. This arrangement enhances the overall voltage output while maintaining the same capacity (amp-hour rating) as a single cell.