This tutorial can teach you how to make a fruit battery and it verifies the low power consumption of the FireBeetle Board-ESP32.
Verification for Low Power Consumption of Firebeetle Board-ESP32
Modify the program to let the ESP32 chip to immediately enter deep sleep at low power consumption after power-on. The sleep lasts for 2 minutes. Restart the chip 2 minutes later.
Connect the negative pole of lithium battery to GND of FireBeetle Board-ESP32 main board, positive pole of lithium battery to positive pole of digital multimeter, negative pole of digital multimeter to the positive pole of FireBeetle Board-ESP32. The lithium battery supplies power to FireBeetle Board-ESP32 through the digital multimeter.
Current tested: 11.897uA.
Conclusion: The current of the whole module is about 10 uA when FireBeetle Board-ESP32 main board enters low power consumption.
Power Supplied by Fruit Battery
The fruit battery is made of lemons, copper plates and galvanized iron nails. The copper plate serves as the positive pole and the iron nail serves as the negative pole to replace the original lithium battery for power supply (ESP32 cannot be driven by the fruit battery when started due to large current, so it shall be driven by the lithium battery. After ESP32 is started, replace the lithium battery with the fruit battery for power supply).