Face it, the Nintendo 3DS stinks for battery life. Let's not pretend it doesn't matter, or that it's okay because we're getting nifty no-glasses 3D, or, you know, put lipstick on a Tepig. The 3DS is a power suck, and speaking strictly in those terms, a big step backwards for Nintendo.
I'm lucky if I get four hours out of the thing, playing with 3D mode engaged. It recently died on me while racing to complete a hang gliding course in Pilotwings. There was little warning, just the blinking power light--unnoticed until too late, as I was intent, by design, on the 3D screen--before a resounding pfft, unit dead. I've since only dared unplug it from the wall socket behind my chair to clock and re-clock its battery in various games.
Update: PCWLabs tested the battery life of Pilotwings Resort 3D (gameplay looped) and found the following.
175 minutes - Full 3D, WiFi, max. brightness, full volume
262 minutes - No 3D, WiFi off, min. brightness, volume off, power-save mode enabled
So between 3 and 4 hours of battery life--slightly more if you slide the 3D lever off while you're tapping around text screens between gameplay. Those are numbers you'd call "okay" for a Windows laptop, but kind of a disaster for the handheld successor to the DSi (9 to 14 hours) and the DS Lite (15 to 19 hours). Even Sony's PlayStation Portable puts it to shame. With the 3200 mAh extended battery, I can do an international flight to Amsterdam (about eight hours from Detroit) of uninterrupted play, and since I'm thinking about Jeanne D'Arc here, I'm talking gate to gate. Even my comparably bulky MacBook Pro averages seven straight hours when I'm on the go.
I guess I'm spoiled. I'm just not used to gizmos crapping out in the sub-five zone, especially not a gizmo that fits in my palms. The bundled cradle helps, sure, but it only makes recharging a little easier.
We know why the battery's such a problem, right? LCD screens sap the lion's share of battery life in most handhelds. The 3DS employs an auto-stereoscopic LCD screen, which means it has to transmit the same, slighty offset image to each of your eyes, separately.
Nintendo R&D engineer Rjuyi Umezu says that means "the amount of light delivered to each eye is halved," and that "[i]n order to make it look just as bright as usual, you have to increase the brightness of the backlight, which increases the power used by [the 3DS] even more."
It's not as simple as it sounds, of course. You don't get 9 to 10 hours of battery life when you play 3DS games in 2D mode, or even older DS and DSi games, all of which average 6 to 7 hours in my tests.
To be fair, Nintendo's always admitted as much--they said the 3DS would average 3 to 5 hours from the start.
Consider this a heads up, in case you've missed any of the discussion around this. It doesn't make playing the games themselves any less interesting or exciting, but it does splash cold water on hopes of playing 3D games for extended periods on the go.