It depends on which model you have. 


At full volume, the Original DemerBox should last 50 hours. The new DB2 model at full volume will last for about 40 hours of playback.


Remember, if you're charging a device at the same time, that playback time will decrease. But you should still get a great many hours at max volume. We've assembled a brief DemerBox Battery Tutorial to give you some tips and tricks about battery life.