TH05 Temperature humidity lithium ion battery box

"I designed a box to use a rechargeable 18650 lithium-ion battery with my TH05 Chinese WiFi temperature and humidity sensor. This setup should provide more than five years of battery life, even with a lower-quality 18650 battery.

The battery voltage ranges from 4.2V to 3V, while the sensor operates within 3.8V to 2.5V, with optimal performance at 3.3V. By using a Zener diode with a voltage drop of around 0.4-0.5V, I can safely power the sensor with the battery.

Almost any Zener diode can be used. A standard diode, which has a voltage drop of about 0.7V, could also work but might prevent the battery from fully discharging.

The backplate can be printed in a single color.