If you are thinking about getting a power grip MB-D12 it can take an EN-EL15, 8 AA cells, and an EN-EL18. you will need adapters for the AA cell and for the EN-EL18, about $75 each. If you buy the EN-EL18, you need to buy a charger, unless you have a D4. As for AA cells I would recommend precharged batteries because they hold up their charge for a couple of years, instead of the regular NiMH batteries, which discharge in about a couple of months. The specs of the D800/E claims that with the MB-D12 you can get 6 fps with AA batteries or the EN-EL18.