8.Boost Converter

Solar MPPT Charger (CN3791)

A solar Li-ion battery charger PCB using the CN3791 MPPT IC, designed in KiCad 8. Optimized for single-cell Li-ion charging from small solar panels with automatic maximum power point tracking.

Features

• CN3791 MPPT solar charging IC
• Single-cell Li-ion / Li-Po charging (4.2V)
• MPPT for maximum solar panel efficiency
• Charging current up to 2A (adjustable)
• Charge status LED indicator
• Compact SMD design

Specifications

Project Structure

├── Schematic/       # KiCad schematic (.kicad_sch, PDF)
├── PCB/             # PCB layout (.kicad_pcb, .kicad_pro)
├── Gerbers/         # Fabrication files
├── BOM/             # Bill of materials (CSV)
├── 3D/              # 3D model (.step)
└── Images/          # PCB renders and schematic screenshots

How It Works

The CN3791 tracks the solar panel's maximum power point using a resistor-set voltage reference on the MPPT pin. It implements CC/CV charging — constant current until the battery reaches 4.2V, then switches to constant voltage. This ensures the solar panel always operates near its peak power output regardless of battery state.

MPPT Voltage Setting

The MPPT input voltage is set by a resistor divider on the MPPT pin:

V_MPPT = 1.205 × (1 + R1/R2)

For a 5V panel with ~4.5V MPP: use R1 = 270kΩ and R2 = 100kΩ.

Bill of Materials (Summary)

Fabrication

Gerber files are in /Gerbers, ready for JLCPCB, PCBWay, or similar.

License

This project is licensed under the CERN Open Hardware Licence Version 2 - Strongly Reciprocal (CERN OHL-S v2).

Author

Abhi90808 — GitHub Profile