[TimGremalm]

Estimated 8.6h with idle CPU, based on my calculations. Raspberry Pi A+ 0.52W usage at 100ma 5.2V on CPU idle (http://raspi.tv/2014/raspberry-pi-a-how-much-power-does-it-n...)

Adafruit PiTFT - 2.8" Raspberry Pi Touchscreen with full-on backlight the current draw is ~100mA. (http://www.adafruit.com/product/1601) 0.15=0.5W

Powerconsumption of Rpi and TFT should be 1.02W at idle.

PowerBoost 500 Charger - Rechargeable 5V Lipo USB Boost @ 500mA+ (http://www.adafruit.com/product/1944) 2.500Ah 3.7V LiPo 3.7V2.5Ah=9.25Wh Boosted to 5V at 95% efficiency 8.79Wh

8.79Wh/1.02W = 8.6h

*Edit: I did a mistake when I calculated the Watt-hour. The Watt-hours of the battery can't increase just because the voltage increases, changed it.

[jsherer]

You should let it run idle and see how long until the battery is depleted. I underestimated the losses due to efficiency with my Libretto project (boost converters run at different efficiencies depending on the power draw).

I was able to get about 4 hours on a 6600mAh battery pack powering a Pi and a 7" touchscreen with wifi and bluetooth enabled (the project draws about 8W when the screen is turned on, about 5W with it turned off).