Battery wont hold charge

Try this:

Plug your phone into the charger and then plug the charger in.

Goto:

Settings
Battery

Look to see if it says Charging on USB or Charging on AC.

If you are plugged into a charger (not a USB port) and it says Charging on USB then try a different USB cord, until it says Charging on AC.

If nothing helps, then change the charger and try it again.

Cords wear out over time, and so do chargers