gordon77 wrote:I'm considering battery power and was thinking about simply monitoring the battery volts, with a simple resistor divider, into a GPIO input so when the monitored volatge drops below the threshold on the input (<2.5v ?) it will be detected by the program (python etc) and do a shutdown.
at 2.5V the raspberry is far (far..) from working.
Raspi input is not tolerant, as B.Goode said you have to feed something within 5% from 5V (i thought even less)
Said that (that, i think, is the really big part of the problem), you should sense battery voltage with an ADC. A simple PCF8574 board is near 3$. I guess 8bit precision is good enough for this
You'll have to manage voltage in the 5V range and signals in the 3,3V range, of course.