The large battery assembly is held in by five T5 Torx screws.

Apple claims that the battery will last up to five hours with active use, and up to thirty days in standby.

This battery is 35 watt-hours. Previous revisions of 13" MacBook Air machines have included 37 or 40 watt-hour battery packs. Since this Air has a smaller screen and lacks a spinning hard drive, we'd expect run time to be somewhat better than earlier Airs.