Phil, Assuming these are AA sized batteries it should do fine. You'll probably have to leave the charge on about twice the time as for NICADS as NIMH batteries usually have nearly double the capacity of NICADS.
If the charge is a "fast charge' type, in other words if it charged the nicads in just a few hours not over night, then it may not do so well as fast charge systems work in different ways. Try it, check that the cells don't get excessively warm, and you'll probably be fine. tom Net-Tamer V 1.13 Beta - Registered