We selected this specific 5V output module instead of a basic charger because our particulate sensor requires a stable 5V supply to ensure its internal fan operates reliably. Since the batteries can only provide up to 4.2V, this module boosts the voltage to the required 5V.
In addition to charging the batteries, it plays a key role in power management. The prototype can remain connected to a wall power source, and if the cable is disconnected for portability, the system seamlessly switches to battery power without interrupting the ESP32.
In essence, this module acts as the bridge between the device, the charger, and the batteries—all while maintaining a very low cost.