The MH-33 Battery Charger is designed specifically to charge EN-EL18d, EN-EL18c, and EN-EL18b rechargeable Lithium-ion batteries. The MH-33 connects to the EH-7P charging AC Adapter which plugs into a wall outlet.
The MH-33 can perform calibration of the batteries; and can fully charge an exhausted EN-EL18d battery in about four hours.
The MH-33 battery charger cannot be used to charge older EN-EL18 or EN-EL18a batteries.
Note that Nikon EH-7P AC Adapter is required for charging EN-EL18c, and EN-EL18b batteries. Other AC Adapters not guaranteed to work.