You can buy these in your local store; we offer them here as a convenience. When using your Alice 4.0 outside, regular AA alkaline batteries will have a short life. Energizer Ultimate Lithium 1.6v AA batteries are recommended for use for your Alice 4.0 when placing outside. (This is NOT the right battery for Alice 1, 2 and 3; those require ONE 3.6v lithium metal battery).