If you go for the larger cacity batteries treat yourself to something like a Trition II or Triton Jr that will charge at 10 % of the pack's rating. In a pinch you can "boost" it and charge a pack in two hours (you have to program out the default 90 minutes on the Jr and that's a 45 second nuisance routine that shouldn't be necessary). $80 to $130 initial investment but worlds above the wall-wart charger that came with your tx.