Brian O - David was right ~ RHF

Think of it like this :
A 40 Watt and 100 Watt incandescent Light Bulb may both fit in the same
Standard Light Socket -but- Their Internal Resistance is different
along with their Power Consumption and Dissipation. The same size
NiCad and NiMH Batteries may have the same outward physical
characteristics -but- Their Internal Electrical Characteristics are
Different and thus a Charger built for a NiCad Battery with not
effectively work for a NiMH Battery and may be in-fact Hazardous
{Un-Safe} to do so.