Where do you often play you car?? (this is a alternative question... See I m from HK as well... and see if I know you..)
usually, a output voltage of the charger on most recent GP3300 will be arround 8.9V, some of them will be lower. The main reason for the high output voltage is the high IR (resistence), most caused by some dead cells (what kinda 3000 cells you've got?? Sanyo or Panasonic? where did you got them??). Sometimes one dead cell in a pack will make the charger's output voltage go over 9.5V... But 11V+ is not a usually case... are you sure it is the output voltage or input voltage of the charger??
Have you check if the program is for Nimh or else??
A whole new pack of batteries need to discharge before charge it. In most case, we'll cycle the batteries (discharge -> charge -> discharge) before really start to use it. This action will stablize the condition of the pack.
Well come to PM me for any local question.
Trying very hard to jump back into RC with CRC Xti-wc.