Alienware 17 R3 - Charger Plugged in and out while playing...

I've changed the battery since it was not charging anymore. now it looks fine, but after a while I noticed that only when I play...
i cannot charge the battery. because it keeps "unplugging & plugging" itself...
it makes gaming hard. it heats up and shuts down. and more probably this is the reason it's happening.
Is it the charger and its time to change it?
or what else could be triggering this unstable "charging" plugged in?

[@litoid]

If anyone needs this - new charger from eBay (dell OEM at $32) did the job. It works now and i can play again.