Help charging tablet loses % while playing

[OvidiuHiei]

Ok so the tablet is brand new, first it had the " problem" where it wouldnt say it had more than 1% even though it could stay for 30m at 1%, then i let it charge overnight while it was off and it went to 100%
now i put it to charge again and while playing games instead of going % up it goes down? its like it cant keep up with the charging while playing a game, is it normal or should i go to the store to get it replaced?
Also should a tablet be charged while its turned OFF?

 

[chanchan05]

Depends on what game you are playing. A particular graphics heavy game being played may indeed cause this event.