The internal battery is a 3.7V 1100mAh 4.07Wh Li-ion battery. If you wanted to do some marathon stuff away from power, you could use a USB-battery backup like the 60Wh HyperJuice. 60Wh / 4.07Wh * 2.5h would give you roughly 36h of usage. Then storage would be your next concern. It can take up to 32Gb SD cards and depending on your type of recording style (video, time lapse, burst, etc.) and settings (1080p, 720p, WGA, 5MP, etc) you will get different amount of usage. With mine, I can take up to 5,000 pictures at 11MP with the 32Gb SD card. Haven't been to the track with the car yet to try the video settings.