Arduino does not work on battery
Did you make sure the battery is charged? Does it have enough voltage to power the board? Remember that Arduino has internal voltage regulator, so you need something little more than 5V in order to get it working okay.

(Comment by bpinhosilva re-purposed as an answer so this will stop showing up as unanswered).


  @bpinhosilva you are right, the battery was not supplying enough power to make arduino work.


Please accept this so that the number of unanswered questions goes down. :)