Just to balance the cells you can use one of these
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXCVEU&P=FR&gclid=CO61mvzmtdECFY17fgod cSwCcg
It'll take a while but if the cells are recoverable it should eventually Balance out. If not, toss the battery