AnimateBattery is a tweak that will add an animation to the battery charge icon that appears on the lockscreen when you connect your iPhone to the power adapter. You also have several configuration options, one with a more complete animation where the battery will charge from zero to where it is at that moment and another more discreet where the battery will move in a much smaller margin. In the video you can see both options perfectly.
You can download it free en Cydia.
You need to have done the jailbreak.