Intel Edison: Measuring USB voltage on breakout board

I have been trying out a variety of power sources. One is the 4xAA battery holder to female USB Verbatim 97928 available for about $10. It seems to have a well regulated 5.0 volt output.

Intel Edison voltage power measure point
Voltage input measurement point for Intel Edison.

The red arrow points to the side of the “74” diode that comes right off the micro USB connector. I measured 5.00 Volts there with the Edison running on the Verbatim 97928. On the other side (downstream) of the diode I measured 4.72 Volts with the Edison idling. This voltage drop is expected due to the forward bias diode voltage drop.

Under 100% of one core CPU load, I measured 4.98V on the USB side, and 4.66V on the Edison side of this diode while powering from the USB port on the Verbatim 97928. The minuscule apparent 20mV voltage drop on the battery/USB side of the diode is likely to come from ohmic losses in the USB connector and cable.

Intel Edison alkaline battery life

Based on measured Intel Edison power consumption, and assuming 2000mAh for an AA battery, I estimate 10-12 hours of battery life on four AA alkaline batteries assuming continuous 100% CPU of one of the two CPU cores (other core idle). Normally the Edison will be mostly resting, drawing perhaps 100mW.

Thus with mixed use, I might expect to get up to 4-5 days of continuous mixed use operation on 4xAA batteries for the Intel Edison.