but yes you do have to mess with the pcb. if you dont you will not be able to charge the 2.4v that the 2 batteries needs. this is the 2 battery turbo mod. not the mod to make it run longer. the batteries are wired in series not parallel. if they were wired parallel then leaving the controller would be ok, it would just take mulptile charges to get the batteries fully charged.
description of the 2.4v battery mods here