Here is a link to Zip Charging on RC Groups... Dan Baldwin of Baldwin controls makes a board to cut off voltage so you don't over charge your packs... Great thing is... No charger needed only a length of lamp cord to control the amps.. Longer cord for wimps or a short cord for us with Kahonas :-) hehe... And if you want to be safe one of Dans boards that you can build for $10.00 or you can just monitor the voltage with a volt meter.
http://www.rcgroups.com/forums/showthread.php?t=747911&highlight=dan+baldwin Craig