I thought I might be able to power an Arduino Due with this, but am skeptical after giving it a try.
I loaded the “fade” sketch and had an 10mm LED and 220kΩ resister on pin 9, soldered the 3.3V jumper on the PowerCell, hooked up SFE’s 6Ah battery, and connected the grounds. The VCC went to the Due’s 3.3V pin.
The results weren’t good. First, the Due’s “L” LED (associated with digital pin 13) was only sort of half-bright, when normally it is full bright with other power sources. Also, the sketch wasn’t running. The LED on pin 9 was at full bright. So I pressed the reset button and then LED on pin 9 burned out.
Due’s regulator was bypassed using the 3.3V pin, but the PowerCell’s regulator should have taken its place. Maybe someone can explain why not. I don’t think I can use this to make a LiPo-powered Arduino — it was kind of an expensive lesson.