Yeah I only have 3 Nitros left myself...At least if you dont factor in the nitros that I dont have engines for that I plan on converting to electric lol. Hell one of the 3 nitros I do have left is pretty much a shelf queen at this point do to parts getting hard to find.
I never built any of those. I used to build stick packs a fair amount and rebuilt tons of battery packs for cordless drills and the like but I hardly touch NiXX anymore. Even for my nitros I tend to run LiFe or LiPo packs.
Ahhh I didnt realize that those hump packs used 2/3A. I thought they used Sub Cs. Didnt even register in my brain that 2/3A was referencing a cell size cuz I havent messed with any non standard cell sizes in years now.
I generally use LiFe or LiPo packs for receiver batteries but you can buy 5 cell "hump" packs or even just use rechargable AAs. You can charge any of those with a basic lipo charger.