Default Battery not chargin

Folks,
Please help out, my Nexus is not charging at all. Yesterday when I tried to charge it was stuck at 72% and not going further even after 3 hours.
After some usage it was 52%, then I had it connected to charger and browsed few videos and mail and was still 52% (read somewhere it won't charge when powered on).

Today I powered it off, kept for charge for 2 hours and still shows 52% though it says charging.
What could be the problem here?
I have tried original charger, original + diff cable, 2 different chargers as well.
The same combo of charger works fine with my mobile.

If the battery is the problem then it should have drained when I was watching videos and webpages when connected to charger but didn't.
So am very confused here.

OS: 4.4 Kitkat 2nd update (not 4.4.1 or 4.4.2).

--
Maddy