I don't think it has batteries.
The Segway resembles a scooter, but is based on a sophisticated gyroscope system, with tilt sensors that constantly check the rider's balance at 100 points of the body per second. If you lean forward, it moves forward. If you stand up straight, it stops. It takes only a slight movement on the riders' part to make the Segway move.
The device weighs 69 pounds, travels at speeds of up to 12 mph and runs on a battery. The commercial models, which cost between $7,000 and $9,000 have extra features, such as longer battery life, or pockets where mail carriers can put their mail.
Full article
I think they would be great fun for play and in some climates. I'd hate to have to depend on even the commercial models for serious transportation.