The NiMH batters should be charged at the output rate (2000mah=2amps) as FastEddy says. And you heard right about the Nicd's, they can safely be charged at 2x the output mah. 1500mah=1.5amp x2=3amp charge rate. Just be sure you drain the packs to 0.6volts per cell before you charge them. And if you plan to store the packs for more than a week charge the NiMh to 40% and discharge (drain) the Nicd's before you store them. Also never over charge the NiMh packs, when they start getting warm stop charging them. or get a good NiMh charger with a thermo probe, so it stops charging when they heat up. Great Planes Electrifly Triton charger is great for charging all types of batteries and has thermal shutoff(Probe sold sep.).