Most Bluetooth speakers are designed to be portable and carried around sans wires. Battery life on a particular speaker is primarily a function of its size, the type of music, and the volume at which it is being played. Larger speakers require more power to produce louder sound resulting in larger batteries. Since space is the major constraint in smaller speakers, they usually have smaller batteries. Manufacturers often list typical battery life on a single charge and it can range from anywhere between 10-15 hours on an average approximately.