O2COOL 1118 5-inch Rechargeable Portable Fan with AC Adapter Smart Power Technology: built-in rechargeable batteries, ac adapter (included), or use with 4D cell batteries (not included). LED light shows the power source being used. 5 inch fan blade enclosed in a pivoting fan cage for a quiet and effective cooling. Rechargeable batteries can charge up to 500 times, equivalent to using 150 alkaline batteries. Up to 72 hours of battery life on a typical use on low speed. Battery life will depend on the quality and age of the batteries used.