For over-ear headphone (E7,E7 pro,E8), they have 30 Hours Playtime Per Charge at Bluetooth Mode. A built-in 600mAh battery won't allow your headphones power off, you can enjoy your world without noise for 30 hours' long time. Don't need to worry the power shortage problem on the long travel.If you need replacement, please connect us with email. Support@cowinaudio.com