USB Charging

[Comage]

I have a mobile battery pack charger which charges up one of my phones on Android (a Samsung) perfectly fine. However when i plug in the battery pack to my Sony Xperia SP, the phone does not charge at all.

Also, i have a usb cable from my computer which when i plug into my sony Xperia SP when the computer is off, nothing happens (the USB port has standby power). only when i power on my computer will the phone start charging! 

Anybody knows what is the problem?

[Ashroft98]

The first thing about the mobile battery pack is,are you sure it is compatible? Because some Samsyng sevices uses Mini USB port instead of Micros USB.It might look fit but no,it won't work.

Second,I'm not sure about that.Maybe your phone needs real-time recognition before charging... Which literally means,you have to see the popup on your screen saying "Xperia SP detected" or something like it,before you could actually charge it.
Are you using Sony's USB cable or other cable?

[Comage]

Well, the Samsung phone I have is a Galaxy Ace 2, and GSMArena mentions its specifications as a microUSB v2.0:

http://www.gsmarena.com/samsung_galaxy_ace_2_i8160-4559.php

As for the Xperia SP, well it is also a microUSB v2.0:

http://www.gsmarena.com/sony_xperia_sp-5364.php

But it mentions it is "MHL" , does that make any difference?

Also, for the phone charging via desktop, yes I am using Sony's USB cable. But it just refuses to charge up until I power on my desktop.

It's a real bummer, and I would gladly appreciate any help I can get.