With so many portable devices that we have needing to be re-charged, FUL came up with the idea of the Powerbag Back Pack, which combines a computer back pack with a removable/swappable built-in battery.
There is a regular USB 2.0 socket on the charger, located inside the front compartment, as well as three kinds of cables (micro USB, mini USB, and Apple 30-pin) that are pre-wired inside a zippered, small side pocket. The cables are not very long, probably designed that way to minimize entanglement. They are for charging small USB devices like cellphones, iPods, and MP3 players. The pocket is designed to hold them while they are being charged.
For larger devices like the Apple iPad or Amazon Kindle Fire, you should use the USB port and the appropriate, self-provided cable to charge them.
A proprietary 3000 mAh capacity rechargeable battery is provided with the Powerbag Back Pack. You can order additional batteries (@$40) at the maker's website (wwwdotpowerbagdotcom). There are also 6000 mAh ($50) and 9000 mAh ($60) batteries available. The battery can output a maximum current of 2.8 Amps, so you can charge an iPad which requires 2.1 Amps and another USB device at the same time. Theoretically, you can charge up to four devices at the same time, but charging time will be longer, because the charging current is shared by the devices.
What makes this bag special is the LED charging and battery state indicator embedded inside the fabric of the bag, and the battery power inlet on the bag that allows you to charge the built-in battery without taking the battery out of the bag. You can see what these look like by clicking customer pictures.
To begin charging a device, you first connect the devices to the appropriate cable, then press the power button on the front of the Powerbag for 2 seconds, until the LED's light up to indicate both the battery state and to commence charging. Pressing the power button again would turn off the charging process.
Of course you can also buy a USB battery charger and put it in a back pack to achieve the same function. What Powerbag does is giving you a more integrated and MUCH more convenient package. I also like the availability of additional and higher capacity battery packs that can extend the time I am away from AC power.