Design and build a Raspberry Pi 18650 Li-ion Battery HAT to make your projects portable

This project integrates a power management and conversion circuit directly onto a custom PCB shaped as a Raspberry Pi HAT. At the core of the system is an 18650 Li-ion battery, secured in a dedicated battery holder, which supplies a nominal 3.7V power source. To safely charge and maintain the cell, a TP4056 module is incorporated, taking power from an external source via a USB female jack to manage the constant-current and constant-voltage charging cycle of the lithium-ion chemistry. Because a standard single-cell Li-ion battery operates between roughly 3V and 4.2V, its output is too low to directly power a Raspberry Pi or Raspberry Pi Zero 2 W, which requires a steady 5V supply. To bridge this gap, the circuit uses an MT3608 IC-based boost converter topology. Working in tandem with peripheral surface-mount devices—including an inductor to store and release magnetic energy, a Schottky diode to prevent reverse current flow, and various resistors and capacitors for feedback regulation and filtering—the MT3608 steps up the fluctuating battery voltage to a stable 5V output. A slide switch allows the user to manually control power delivery to the system, enabling a portable and self-contained power solution for embedded computing tasks.