What is advantage of NiMH battery?

Memory effect occurs when a sintered-plate nickel-cadmium (NiCd) battery is repeatedly discharged to a particular level above a full discharge, that is, only "partially used", and then recharged to an equally precise "full" level. This "real" memory effect is extremely rare and is found only on very expensive, rare, and older unattended electronics such as communications satellites (which repeatedly use exactly the same amount of power while in the Earth's shadow). Repeated attempts to duplicate it in the lab have proven difficult.