How do i know when i need a new charger for my phone

Solution
It may well not be the charger. It could be the battery, and if it is charging but really slowly, it sounds much more like the batter is the problem.

If you have or can borrow another charger cord and see if that will make a difference, and also try yours in another device, that should let you know if it is the cord. But to be honest it seems more likely it is the battery. They start to charge less and less, and hold less and less of a charge, when they start to go.
It may well not be the charger. It could be the battery, and if it is charging but really slowly, it sounds much more like the batter is the problem.

If you have or can borrow another charger cord and see if that will make a difference, and also try yours in another device, that should let you know if it is the cord. But to be honest it seems more likely it is the battery. They start to charge less and less, and hold less and less of a charge, when they start to go.
 
Solution