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 and EN-EL18a 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.