green laser power drop

Hello, I am fairly new to the world of lasers. I saw the pink floyd laser spectacular about 3 weeks ago and have been hooked on lasers since. I recently bought a green laser pen from radio shack and stuck it into a device i made. All i modded on it was i unscrewed the battery part and made it externally powered from a battery pack. I didn't change out the driver or anything, and there is a problem with the laser being on too long. The beam starts becoming much much weaker and i have to turn it off for a bit but it still doesnt stay full power too long. Could it be over heating? or should i build it a new driver? I plan to make it powered from the same 12v power going into the device its in but i didnt have enough time to put the circuitry together (i had to take it to my friends house to have an awesome laser party). Any help would be much appreciated, i am eager to learn.

^Read the sticky in this (green laser) section. Here's a link: http://www.laserpointerforums.com/laser_pointer_forums_3/forum/showthread.php?t=30682


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