Thie thing about batteries is this: You can have the proper voltage, but if the Amps are not there, they are not going to work well. It is possible that they both got burned up. How long were they on the chargers? According to the manual, you should leave them on for about 2 to 2-1/2 hours or till they begin to get warm. If they were hot, then it is totally possible that they are both fried.

If possible, I would recommend switching to Lipo's. But make sure you follow the directions for them. If you leave the house with them charging and not supervised, you may come back home to no home at all.

Take care and good flying,