I too am instrumenting a hive to monitor the location of the winter cluster, using custom frames with embedded temperature sensors, and an Arduino Mega to do the scanning, and an Xbee network to get the data back to the house. The frames also have a resistor network embedded in case adding a little targeted heat might help a near-frozen cluster move to nearby honey stores. Like you, I am planning on power from a solar panel and storage battery. I'm concerned about outdoor heat and cold on a LiPo battery; what kind are you trying? The latest Make Magazine issue had an article about how a guy in Virginia handled temperature extremes for his outdoor solar/battery/electronics boxes; it is kinda wild. (I'm also setting up a RPi system, but not planning on using it for the hive monitor.) I'd like to share approaches and experiment results, including your battery voltage monitoring. My email address is public in this forum, firstname.lastname@example.org
. Hope to hear from you, and anyone else interested in using Adafruit products and training for beekeeping.