From Nikon
MBD 10 For NIkon D300 Digital Camera includes MS-D10EN for use with EN-EL3e battery (sold separately)
It comes with two battery trays: one holds an EN-EL3e 7.4v 1500mAh lith-ion battery (same as what the camera holds). The other tray takes eight, AA batteries. Depending on which AA cells you install (Ni-MH, lithium, Ni-MN or alkaline) you can have 9.6 (NiMH at 2500mAh or more) or 12 volts. That voltage can crank the motor to its rated limit of 8 fps...at least until the buffer fills up and its frame rate slows while it writes to the card. You also tell the D300 via the menu which type of battery you have installed. It keeps track of charge for you based on the type. Very smart.