3.7 volt battery = 1 cell x 3.7 volts (1S)
7.4 volt battery = 2 cells x 3.7 volts (2S)
11.1 volt battery = 3 cells x 3.7 volts (3S)
14.8 volt battery = 4 cells x 3.7 volts (4S)
18.5 volt battery = 5 cells x 3.7 volts (5S)
22.2 volt battery = 6 cells x 3.7 volts (6S)
29.6 volt battery = 8 cells x 3.7 volts (8S)
37.0 volt battery = 10 cells x 3.7 volts (10S)
44.4 volt battery = 12 cells x 3.7 volts (12S)

520KV RPM/Volt
battery lipo 7.4V

540Kv * 7.4V = 3996 rpms

[12800mAh / 1000] * [1 * 11.1V] / 1W = 142.08 Time
12.8 * 11.1 / 1 = 142.08

Time = [mAh / 1000] * [# of batteries * battery voltage] / device power
Device is rated at 1W using 4 AA [1.5 Volt] batteries rated at 1000mAh.
Time = [ 1000mAh / 1000 ] * [4 * 1.5 Volts] / 1 W = 6 Hours

References:

http://en.wikipedia.org/wiki/Brushless_DC_electric_motor#Kv_rating