I am happy to report that the two outdoor super capacitor projects I assembled based on Felix's design continue to run flawlessly outdoors, during extended periods of single digit temperatures.
I agree. We've had a week to week and a half of below 0 deg F and some lows below -10 F. My outdoor Mote / supercap + solar panel hasn't dropped below 5v.
Good to know how this setup is working for you. Right now I have a Moteino + Weather shield running on 3 AA Eneloop batteries for the last 126 days. The temp in SD is -15 F and the batteries are doing fine. I would eventually to try and give the SuperCap + Solar panel a try. Please keep us updated how this is working for you guys.
A couple weeks ago, one of the two solar supercapacitor projects I made last spring/early summer failed.
Since the voltage from the way-too-big solar panel had been consistently driving the voltage to 5.6v or more, I immediately suspected my poor 5v super-capacitor.
I had an opportunity today to investigate the cause.
I eliminated the solar cell & super-capacitor from the circuit and instead powered it from an FTDI adapter. However, the device would not stay active for more than 30 seconds. Well, that means the super-capacitor didn't cause the problem.
As I watched the moteino's activity on the serial monitor, it would go unresponsive pretty quickly.... sometimes mid-sentence as it was sending debug lines. Do I have a bad moteino??
Alright, so let's unsolder the BME280. With the BME280 removed, the moteino ran smoothly again. Just to be sure, I reattached the BME280 and sure enough the moteino would lock up again.
So I found the culprit. The BEM280, bought from the cheapest seller on E-Bay, is to blame.
The BME280 is a self-contained chip. Could there be a difference in quality or could something else cause it to fail prematurely?
I'll solder on another BME280 and see how it goes.
However, it's quite possible that my mounting method might have contributed. I've got the sensor mounted unprotected in the center of an Acurite radiation shield:
https://www.acurite.com/solar-radiation-shield.html
It keeps direct moisture out, but that's about it.