you can not find any energy cells in Fallout 3 after you find the ones with the alien blaster, you are limited to that number
it repairs your weapons
alien blaster but ammo is hard to find after you have it all and its at the alien crash site
you go to the alien blaster location and jump on the alien space ship
exactly North of Mine field.
north east of the map in an alien ship
if its the alien blaster you want, its easy to find. watch this youtube video. http://www.youtube.com/watch?v=oTdu5ABpSEE
The only ammo you get is where you get the Alien Blaster. But apparently there is more ammo near a truck where a Mr. Handy is. Hope that helps. :)
On the mother ship zeta expansion pack, if you don't have that you can't get them, besides one alien blaster with limited ammo at a UFO crash site
The alien crash site is under neither Vault 92 and Clifftop shacks. The distance on the radar is about the distance of Clifftop shacks and Vault 92 wide. Good luck.
from the crashed alien ship next to the dead alien
i dont think there is one... sorry