What size packs are they? I charge NiMH packs at 1c no more. Pretty sure the stock Stampede comes w an 8.4v 3000 mah NiMH. I would charge it at 3amps. For your first couple cycles you "could" charge at 1amp...slow and steady..but they are cheap NiMH packs...I just throw 1c at 'em and run 'em. Never had issues. Remember NiMH get stronger after they have been cycled a few times. Also they WILL get hot when at the end of their charge and discharge. Always let them cool to ambient temp before recharging or running them. You should get years of use out of them. My daughters Stampede is almost 3 years old and NiMH is just dying out...so she will be getting a 2s lipo for it.