Q: battery starts discharging after a certain time even when the charger is plugged in

Hi,

I have iphone 5, whenever i charge my mobile's battery with wall charger it starts discharging the battery after some time, despite the icon shows that battery is being charged. I have also tried different chargers and even replaced the battery with new one but the problem still sustains. But when i charge my battery with laptop it charges smoothly..

Can anyone plz guide me through this how to resolve such kind of issue?