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Here is the graph about the 64625 bulb from LuxLuthor's thread. So you can basically use any battery combination up to 14.2V BUT (and a big but) the batteries have to handle the high current. So I recommend you to use 32650 li-ion cells. Normally they are to long for usage in a 3D Maglite. That's why you'll also get the extension when buying the light.
There are no batteries included in the sale.
rayman