Replace batteries of 20 TV remote controls
No, you would not wire them in series. You'd wire them in parallel. You'd tie all the "positives" together and connect them to a 3V power supply's positive output. You'd tie all the "negatives" together and connect them to the same supply's negative (common, ground, etc.) output. The supply would likely not need to supply more than a few hundred milliamps but that's just a guess.