Nikon D1X Digital Camera Battery NiMH (2100 mAh) - Replacement for Nikon EN-4 Battery Replacement battery for the Nikon EN-4, Nickel Metal Hydrate (NI-MH) 7.2V (2100mAh) 100% compatible with your OEM battery - 3 year warranty. Made with high quality Japanese cells. Synergy Digital is a Registered Trademark