On this table are 21 handhelds, including the Vita, PSP and just about every flavour of Game Boy, DS and 3DS there is/was.
The test, conducted by Andy Robertson at Family Gamer TV, is simple. Start them running, and see which one runs the longest.
It's not entirely scientific, as it's slightly unfair to compare the battery drain of a PSP game to a Game Boy one, but then you could counter that it's all relative, and that I'm not a scientist, and that I should just shut up.
A fair point.
For the impatient, the overall winner was the Game Boy Color, which lasts so long it nearly made an appearance on Life After People.
Robertson also wrote about this test for Wired's Geek Dad.
Huge Battery Test [Family Gamer TV's YouTube, via Tiny Cartridge]
[Note: This piece originally did not name Family Gamer TV's Andy Robertson as the creator of this video and only linked to his YouTube clip. We apologize for the lack of better credit.]