The problem is probably due to your wall charger, if you have a generic brand get rid of it and purchase an original one even if it means more money, have your wallcharger checked out. If the phone has received any moisture or it has gotten wet then the problem lies inside in the internal battery and there is nothing you can do, it has to be replaced. Or perform a load test on the battery at your nearest cell phone tech location if the battery fails the test then its the battery.

Good luck.

Lex....