Note: There is no mobile power comes with the backpack inside.
If you want to use External USB Charge Function, you have to do as follows:
1.Buy a mobile power source
2.Connect your mobile power with the USB interface inside the backpack
3.Connect your phone with the USB interface outside the backpack
There are 2 kinds of mobile power in the market.
1:Plug in your phone, you can start charging
2:Plug in your phone also need to press button of mobile power then start charging
To cope with this backpack, we suggest purchase of the first mobile power.