Battery Charger (KiCad)
Battery Module
This project is a compact battery-to-battery charging system, designed to safely charge a 3.7 V Li-ion battery from another 3.7 V Li-ion battery. The goal was to create a portable power-sharing solution using proper power-management techniques, rather than directly connecting batteries, which is unsafe.
The system boosts the source battery voltage to 5 V, then uses a dedicated Li-ion charge controller to apply the correct CC/CV (Constant Current / Constant Voltage) charging profile to the target battery.
How does it work?
The complete schematic was designed in KiCad, including component selection, electrical calculations, and layout considerations for manufacturability.
Boost Converter Stage
A ME2108A50 boost converter steps the battery voltage (~3.0–4.2 V) up to a regulated 5 V (VBUS).
This stage uses an external 22 µH inductor, a Schottky diode, and ceramic capacitors to achieve stable and efficient operation.Battery Charging Stage
The regulated 5 V output feeds an MCP73831 Li-ion charge controller, which safely charges the second battery using a programmed charge current.
The charging current is set via a program resistor, and an LED indicator provides charging status feedback.
Route PCB (KiCad)
3D Model (KiCad)
Main components:
ME2108A50 – Step-up (boost) DC-DC converter
MCP73831 – Single-cell Li-ion charge controller
22 µH Inductor – Energy storage for the boost stage
SS14 Schottky Diode – Fast, low-loss rectification
Ceramic Capacitors (0805) – Input/output filtering
Programming Resistor – Sets charging current
Status LED – Visual charging indication
3D Model (JLCPCB)
