The heart and soul of the Nintendo DS and DSi is its lithium-ion (li-on) battery. No battery, no portability. Here's what you need to know about your Nintendo DS/DSi's battery, as well as some tips on how to keep it healthy, happy, and long-lived.
The charge on the Nintendo DS/DSi's battery lasts about ten hours.You can expect about ten solid hours of gameplay from your Nintendo DS/DSi's battery before it needs to be recharged. However, the DSi's battery is capable of draining its battery faster than the DS because of its added features (camera). Some Nintendo DS owners report that, through careful use, they can squeeze close to 17 hours of use from their battery before it goes on the blink.
Don't let your Nintendo DS/DSi's battery drain completely before recharging.In the past, it was common for an electronics manufacturer to advise users to let a device's battery drain completely before recharging. However, draining the battery to increase its lifespan was true of older nickel-cadmium batteries. The battery for the DS and DSi is a lithium-ion battery; draining it completely before recharging isn't necessary or beneficial.
However, even lithium-ion batteries can only withstand a set number of charges before they start to age. In order to keep your DS at its best performance while minding the battery's overall lifespan:
Heed the power light.Once your battery has about 30% power remaining, the Nintendo DS/DSi's "Power" light will switch from green to red. That's a good time to stop and recharge. Recharging the DS/DSi fully takes about four hours. You can play while you're hooked up to an AC adapter, but doing so adds to the charging time.
Turn off the backlight or adjust the screen brightness.With the original style Nintendo DS ("Nintendo DS Phat"), you can toggle the backlight on and off. The backlight is a big drain on the battery, but if you're playing in natural daylight, there's no need for it. Shut it off if you're conscious of your battery life.
The Nintendo DS Lite and DSi let you adjust the screen brightness up or down. Again, natural light should allow for a lower brightness setting. In a very dark environment, adjusting the brightness to 2 (out of 4) should be sufficient for play, and will save considerable battery power.