ROM Hack Is there battery level app?

[legendofphil]

Is there a homebrew application that could give the percentage remaining of the DS battery?

 

[Mangofett]

It's not possible: The DS hardware can only tell whether it's low or high.

 

[FAST6191]

While linkiboy appears to be correct:
http://nocash.emubase.de/gbatek.htm#dspowermanagement

I am sure you could make something elaborate involving turning on the wifi, sound, mic, 3d, lights and such to make a slightly more elaborate way of testing how much power you have left.

To my knowledge a few minor games functions aside (some games warn you when you hit low power) there is nothing.