Check your computer's software and function before your return date ends! The refurbished Macbook Air I purchased had a defective battery, and would shut down randomly if not plugged into the charging unit. The battery icon on the top toolbar read "Service Battery," and upon checking the computer's Activity Monitor, you are able to see how long your computer runs on 100% battery. A new Macbook Air, when fully charged, holds upwards of 10 hours run time. This computer only held 4-6 hours of run time off the charger.Added a star for their customer service - very responsive and quick.