USB cable can not charging，

Will only charge via USB port on computer - ac/usb adapters do not work.

The adapters only provide + and gnd, the phone requires another of the contacts to trigger the charging.

more specifically- USB devices that follow the spec are only allowed to draw a small amount of power when initially plugged in. THen they are supposed to ask the device they are plugged into for permission to draw more power. (So that they dont overload laptop usb ports and the like.) if the device says "sure go ahead and draw more power" then the phone is permitted to pull more juice. So the saga performs exactly by the spec. So if you plug it into a computer that is capable of says "sure" then it will charge. Otherwise the saga never receives permission so it wont draw more. Basically it stays on tricle charge.

search some more- there were several threads from when the phone originally came out where people posted which cables and adapters where known to work.

Be sure to use the dedicated USB ports on the computer, and not through a hub, monitor, keyboard, etc. because most of these do not support powering/charging a device. I run into this with portable hard drives. They will not work when plugged into a USB port on a monitor like flash drives and have to be plugged directly into the computer.