The Nikon MH-20 is the quick charger for the MN-20 NiCd battery pack which is used with the MB-23 Multi-Power High Speed Battery Pack. The MH-20 can charge up to two MN-20 units sequentially, and operate automatically with voltage from 100V to 240V (with a matching local plug).
The recharging time with one battery attached is approximately 90 minutes, with two batteries about three hours.