Its apparent you have not seem every store in america that sales anything for consumer goods. the shelves are covered with them
ORIGINAL: BaldEagel
Nicads are old stock if you are still using them, they are illegal to dispose of in any standard disposal facility and leak cadmium.
AA batteries of 2700Mah capacity have a high internal resistance and would be very stretched when asked to power only a few Digital servo's, any drop in voltage will be momentary and would not show on a voltage check after the crash as they would recover voltage after the load has been lowered.
Sub-C Nimih batteries are much better able to cope with high current draw.
A123's are the way most are going, I use them exclusively in my jets and have done for four or five years now, no need to remove them when charging (no explosion or fire risk) stable current capacity right up too 2000Mah of the 2300Mah capacity of the large cells and up too 1000Mah of the 1100Mah smaller cells, do not need a regulator for any installation except for some old JR servo's that don't take over 6volts. Most modern charges have a setting for LiFe batteries so no excuse for charging them incorrectly now days.
As with Kero start most modern turbine manufactures are now going over to the facility to use of A123's to power the ECU's as an alternative, JetCat and JetsMunt to name two.
Hope this helps.
Mike