At the Nintendo Switch presentation, Nintendo revealed that the rated battery life for the Switch is between 2.5 and 6.5 hours. On the official Switch website, the company went further and said that The Legend of Zelda: Breath of the Wild can be played for roughly 3 hours on a single charge.
This puts the Switch roughly in line with battery life of the original Nintendo 3DS and original PlayStation Vita. Fans of both portable systems sometimes had issues with game time. It's worth noting that we don't know how the Switch will handle battery drain in standby; while the Vita was very good about power loss in standby, the 3DS was prone to draining away even in Sleep Mode.
One plus is that the Switch is USB-C compatible. The Switch will be able to charge via any standard USB-C cable and the USB Type-C standard should have faster charging when compared to standard USB. According to a translation of the Japanese official Nintendo website, charge time is 3 hours. Yep, charge time is equal to play time in some cases.