Sounds like you over discharged it, it is possible to revive one, but it is 50/50. If your charger has Li-Ion set it to that or Ni-Mh, and have it charge to the voltage on the pack (1S = 3.7, 2S = 7.4, 3S = 11.1, 4S = 14.8 ). After you get there charge it the rest of the way to full on the...