Description The BL-5 Battery Chamber Cover from Nikon is a battery chamber cover that's used with the MB-D12, MB-D17, and MB-D18 Battery Packs and enables the use of an EN-EL18 series rechargeable lithium-ion battery to power the camera. MB-D12 (D810A, D810, D800E, D800)MB-D17 (D500)MB-D18 (D850) In the Box Nikon BL-5 Battery Chamber Cover for MB-D12 Battery Pack