in my experince the high quality NiMh out perform sayos NiCd batteries by a large margin.
go to
www.cheapbatterypacks.com and get som intellect 1400 mah or elite 1500 mah batteries.
then get a smart charger, Graupers ultramat 14 works very well for me. when you recive the battety the first time charge it for 10 hours at 200 mah.
this preps the new cells.
afterwards you can fast charge them up to 1-1,5 A. the delta peak cut off should be set at around 5-10.
i will then guarntee you that you will have a battery that is extremely superior to the Sanyo 600 mah nicd cells.