The USB port does not work well
For a bad, or use undesirable problem such as a fall- it is possible that this connection is not possible condition improvements. Personally I have had experiences where I have seen a USB port blocked or have certain connectors corroded by water. To do a check to make sure everything is in good condition and that is not the problem that causes a slow loading occurs. If what happens is a blockage, the solution is obviously simple, if it is found that there is a serious failure (for which you can test the USB cable to other devices), you can try to clean the connections with a dry cloth or cotton cloth - here is a bastoncillo- best, but usually have to carry a terminal for service).
The battery could be the problem
This can also happen. The truth is that the latest models included in the mobile terminals are of adequate quality, and usually last a long time. But it may happen that have a defective or simply for some reason the slow recharge is because this component. If this is so you can buy a new one for devices that exchange the battery, but otherwise have no one to call for service. One way to detect it is this element that fails is that the percentage of load shown jumps randomly in ranges of different measures (eg having 15% available at 60% in just five minutes recharge). This is a problem that has no easy solution ... other than to resort to change indicated above.