It depends on the charging current required by the mobile device and the age of the battery in this device:
- The greater the charging current required, the longer the charging time
- The older the battery, the longer the charging time
The USB connector of this product gives a 500mA current. Generally speaking, it would take 1-3 hours to fully charge a MP3 player. For tablet, due to a much higher charging current needed, it may take up to 20 hours.