What do you call the bats that police officers carry?

The general name is baton (french for stick). The longer baton (about 28 inches) is a night stick- so called because it was carried by policemen patrolling on foot at night. Although rarely seen today, there was also a daystick- a short club, about 12-14 inches. There is also a riot baton- used in crowd control- about 30 inches long.