RE: Fast charge question
If you want to make your packs last, less than 1C and max .7Amps for a AA cell pack.
A 600ma pack can charge at about .4Amp but the 1500ma pack could be charger at about .7 or .8 amp without damaging the cells with a good peak charger.
If the cells are sub C or larger they can take a faster rate but try to stay less than 1C charge rate.