The Nikon MH-26aAK Adapter Kit includes a BT-A10 adapter and an MH-26a dual battery charger. The MH-26a charges and calibrates the EN-EL18, EN-EL18a, and EN-EL18b Li-Ion batteries for the D4 and D4S cameras, and MB-D12 battery pack. The adapter attaches to one of the slots on the MH-26a and charges the EN-EL4 and EN-EL4a Li-Ion batteries for the D3 series cameras, and the MB-10 and MB-40 battery packs.
Battery Compatibility
EN-EL4, EN-EL4a, EN-EL18, EN-EL18a, and EN-EL18b
