The Ducame EN-EL4 Lithium-Ion Battery Pack replaces the Nikon EN-EL4a battery. Small and lightweight, this rechargeable lithium-ion battery can be charged or discharged at any time without developing memory effects, meaning it will never lose its ability to hold a full charge.
Reviews Ducame EN-EL4 Lithium-Ion Battery Pack (Replaces Nikon EN-EL4a) for Nikon D2H, D2Hs, D2X, D2Xs, D3, D3s & D3X Digital Cameras