What would happen...?

So today I went and bought the "Task Force 3W "CREE" 2C 150+ lumens" that I read about on this forum and began to wonder if there was such a thing as a lithium C sized battery. I found this:

http://www.zbattery.com/s.nl/it.A/id.48/.f

What would happen If I put two of these (=6W) in the flashlight, which is a 3 W light? Would it melt, burn out or just be brighter? Any thoughts?

i would think that the driver or led will go if you double the voltage 3v-6v

First, batteries are measured in 2 main areas, Volts and mAh (milli-amp hours), not watts. You can use volts and mAh to come up with a Wh (watt hours) figure for batteries but that isn't relevant to the discussion here.

A normal C alkiline battery is new at about 1.6 volts. So 2 are just over 3 volts when new out of the package.

The LED in that light requires 3.5-ish volts to light up. So contained in that flashlight is a Boost drive circuit that steps up the voltage. Putting 6 volts won't make it any brighter.

Also those batteries, if I'm not mistaken, are not for sustained high current. They're not for flashlights.