No need to replace batteries over and over again, just simply plug in the cable for 1.5 hours, provides your kitty up to 4 hours of fun time^ The primary purpose of the self rotating ball is to have your pet chase the ball around and have fun. With just a single press of a button, the ball will start to do a 360 degrees self rotation and attract your pet's attention. The ball will continuously move around your house while producing a red light simultaneously^ Due to the sphere shape and self balancing system, the ball will automatically change its direction when colliding with a wall, chair, door, etc. no extra help required, all you need to do is turn the ball on to play and turn off when your pet is out of energy and done playing^ The ball rolls best on hard floor,might not roll well on thick carpet, please purchase with attention^ The ball will automatically turns off after 15 minutes of rolling,perfect for those who dont have time to watch your kitty while they are playing^