Compact Lithium-ion power supply for the Nikon D2H. Up to 2,900 images can be shot on one charge. The EN-EL4 is free from ‘memory effect’, so it can be recharged at any time or any level and it features discharge cycle characteristics that extend the battery life. A microchip built into the battery measures discharge capacity and compares it to the full (maximum) capacity recorded when the battery was last calibrated. To charge the EN-EL4 use the MH-21 (also supplied with D2H).