Just the one batteryI've heard they can last a long time. I went to a two day event with one battery and it had no problems.
Sorry, what I meant was one lot of batteries (x3)Just the one battery
When i first picked up a rotor a few years back, played a whole season with the same batteries in, had no problems. When the new season started, rotor was still feeding fine, i still changed them out just to be sure they dont fail half way through a game.
3x AA batteries are cheap enough