We want to use alkaline batteries to power the BB long enough to self shut itself down when a power brownout/outage occurs. Our system makes frequent writes to the SD card and want to prevent possible corruption should power be lost in the middle of a write operation.

We would like to use the battery connection to the PMI, however we do not want any charge current to flow to the battery since they are alkaline. The battery input provides a greater acceptable voltage range (2.7V to 5.5V based on PMI specs). If we use a diode to ensure unidirectional flow, will the PMI treat this as a fault such as a "no battery connected" condition? We would substitute a resistor for the thermistor indicating a proper temperature condition.

Any help or suggestions would be greatly appreciated.