You might want to check out chargers that have mv and amperage rates that are adjustable. If you looking for a budget charger then i would check out this
http://www3.towerhobbies.com/cgi-bin...&I=LXRST9&P=ML or this
http://www3.towerhobbies.com/cgi-bin...&I=LXTSA4&P=ML and another good one as well is also this
http://www3.towerhobbies.com/cgi-bin...?&I=LXCLD5&P=7 and another good tip is that if you store your batts for a long period of time please make sure to cycle your packs.