The initial experiment is done in fridge and oven, proven OK but not pushed to the limits. Kevin, our product engineering manage took one armored stalker back to home town in freezing northeastern China for Chinese new year. It stayed in the wild for 10 days, record down temperature and its voltage every 5 seconds.
Seeeduino Stalker V2 (The temperature measuring is done by temperature sensor integrated in Stalker.)
2000mAh Li-Po Battery