Thanks to the great help I have received from the community. I have completed the design and 6 months of testing for an Electron Carrier board optimized for outdoor use. I have documented this on Hackster.io on this Project Page.
In short the board has these features:
- Circuit protection on all external lines
- push button power for DC-IN and LiPo
- Hard reset functionality - the Electron can power-cycle itself
- 256k FRAM memory
- TMP-36 temperature sensor
- 5V Boost converter so it has both 3.3V and 5V i2c busses broken out
- External watchdog timer for extra reliability
If anyone has comments, suggestions or requests for the next version, please feel free to comment here or on Hackster.