LT3652 MPPT Solar Battery Charger

A professional-grade solar-powered battery charger designed around the Linear Technology LT3652 power tracking battery charger IC. This open-source project provides a complete solution for efficiently charging 3.7V Li-Ion/LiPo batteries using solar panels.

✨ Features

• 🔋 MPPT Technology: Maximum Power Point Tracking optimizes power extraction from solar panels
• ⚡ High Efficiency: LT3652 IC provides efficient power conversion with up to 95% efficiency
• 🔧 Configurable: Programmable charging parameters for different battery types
• 📊 Status Indicators: Dual LED system for charging status and fault detection
• 🌞 Wide Input Range: Supports 6V-18V solar panels (tested with 12V, 250mA panel)
• 🔒 Safe Charging: Automatic termination and battery protection
• 📦 Compact Design: 35x25mm PCB with professional layout

🛠️ Technical Specifications

Key Components

• Main IC: LT3652 Power Tracking Battery Charger
• Input: 12V, 250mA Solar Panel (compatible with 6V-18V)
• Output: 3.7V Li-Ion/LiPo Battery (configurable float voltage)
• Inductor: 10µH shielded power inductor
• Connectors: JST battery connector, screw terminals for solar input
• Indicators: CHRG (red) and FAULT (green) LEDs

Circuit Design

• Online access

Charging Parameters

• Charge Current: Programmable up to 250mA
• Float Voltage: Configurable via FB pin resistors (default ~4.03V for safety)
• MPPT Voltage: Adjustable via VIN_REG pin (default optimized for 12V panel)
• Termination: Auto-restart when battery voltage drops 2.5% below float voltage

🎥 Build Video

A complete build guide and tutorial is available on YouTube, Watch here.

📄 License

This project is licensed under the MIT License - see the LICENSE file for details. You are free to:

• Use commercially
• Modify and distribute
• Place private use
• Use without attribution

🤝 Contributing

We welcome contributions! Here's how you can help:

• Fork the project
• Create a feature branch (git checkout -b feature/AmazingFeature)
• Commit your changes (git commit -m 'Add some AmazingFeature')
• Push to the branch (git push origin feature/AmazingFeature)
• Open a Pull Request
• Direct Design Feedback
• You can also provide direct feedback on the PCB design through our shared Altium 365 project.

🐛 Troubleshooting

Issue Possible Cause Solution

• No Charging SHDN pin not enabled Connect SHDN to VIN
• LEDs Off FB resistor network incorrect Verify 250kΩ equivalent resistance
• Overheating Inductor saturation Use 500mA+ rated inductor
• No MPPT VIN_REG not configured Check resistor divider values

👤 Author

Chris

• YouTube: @DIYGUYCHRIS
• GitHub: @DIYGUYCHRIS

🙏 Acknowledgments

• Analog Devices for the excellent LT3652 IC and documentation
• JLCPCB for reliable PCB fabrication services
• Altium for providing professional PCB design tools
• Open Source Community for continuous inspiration and support

⭐ If you find this project helpful, please give it a star on GitHub!