Arduino uno with official Wifi Shield take 5 Volts. Arduino lights up as it should when powered but the WiFi shield is dead the l9 doesn't light up but works fine when arduino is connected to usb cable.
I use 5 battery holder 5x1.5V = 7.5 V ; 2000 mAH
50 mA - Arduino 300 mA - WiFi shield 350 mA * 5h = 1750 mAh 5xAA = 7.5V ; 2000 mAh
Am I missing here something? It should last in the worst case scenario 5 hours with new batteries at 2000 mAH (which I think they have more but I do not have them on me right now).