Yesterday evening the ESP8266 the data logger connected for the last time to Thingspeak and posted temperature and humidity. It has reported these values every 10 minutes for 2045 hours or in other words 85 days. This is nearly 3 months!
ESP8266 posting temperature and humidity every 10 minutes
for almost 3 months on 3 AA batteries
In the last few days the DHT11 had started reporting bogus data, probably the voltage was insufficient to do a correct reading. While the reported temperature continued to look reasonable until the end you can’t say the same about humidity. It kept toggling between 95%, 43 and 0%.
All in all I’m very impressed that the setup could last so long. It was so stable that it would run on its own, without ever restarting it. In the same duration I had misconfigured my access point and had to set it up again and my internet provider had produced a 10 hour “internet blackout”. Now the three cells have each a voltage of about 0.9V.
Maybe with a few additional tricks and without the AP/ internet blackouts the batteries would have lasted longer (fix IP, feeding DHT11 voltage through GPIO pin, etc). But it’s already an impressing duration for a simple setup.