First thermostat runtime test results

The good news is that with the eInk display, the Feather is able to run longer than the target goal of 72hrs.

From start of test, until approximately 81 hrs in, the measured voltage off the Feather appears to match the shape of what I would expect for a LiPo cell. However, from hr 81 to 85, the Feather continued to run and report approximately 3.5v, however this value didn't change (which seems unlikely) - I'm wondering if this is an artifact of the 3.3v regulator needing 0.2v drop to operate and the ARM processor measuring from Vin and assuming that was 3.3v (even when it was lower).

On plugging in USB power again and charging the LiPo cell, the Feather reported 3.14v as the first battery reading. 

Currently logging charge voltage curve.

Next test will be replacing the eInk module with an OLED module and performing the runtime test again.