Single cell lithium battery charging module with CN3791 MPPT regulator for 3.7V nominal and 4.2V full charge. Designed to accept lowvoltage solar panels or DC sources with nominal inputs of 5V, 6V, 9V, or 12V. Updated 2025 module focused on reliable charging and improved conversion efficiency for small solar charging systems and DIY projects. Key benefits Efficient solar charging: Builtin MPPT tracking optimizes power extraction from the connected solar panel, improving charge performance under varying light conditions compared to simple directcharge circuits. Safe singlecell charging: Configured for one lithium cell with standard 3.7V nominal and 4.2V charge termination, providing proper charging profile for singlecell lithium chemistry. Broad input compatibility: Works with common smallpanel voltages of 5V, 6V, 9V, and 12V, allowing flexible pairing with a wide range of panels and DC power sources. Compact and easy to integrate: PCBmounted regulator module fits into portable projects, charge packs, sensor systems, and or prototype builds. Reliable control and regulation: CN3791 MPPT controller provides stable charging control for consistent performance in offgrid and portable applications. Features and specifications Charging target: single lithium cell, nominal 3.7V, charge cutoff 4.2V Controller chip: CN3791 MPPT regulator Input voltage compatibility: nominal 5V, 6V, 9V, 12V solar panels or DC sources Function: maximum power point tracking for optimized solartobattery conversion and regulated charge control Module form: PCBmounted regulator controller module suitable for integration into DIY and small system assemblies Practical applications Portable solar charger: Pair a small 5V to 12V solar panel with this module to maintain and charge a single lithium cell for portable lights, power banks, or field devices. Offgrid sensor or telemetry node: Use the module to keep a singlecell battery charged from a modest solar panel on remote sensors, data loggers, or wireless beacons where consistent charging under variable light is important. DIY and projects: Integrate the module into hobby electronics, prototype power supplies, or to basic charge circuits when upgrading to MPPT control for better energy harvesting. Installation and usage notes Connect the solar panel or DC source to the module input and the single lithium cell to the module output following correct polarity. Confirm the panel nominal voltage matches one of the supported input ranges before connecting. Designed for singlecell lithium chemistry; do not use with multicell lithium packs without appropriate balancing and protection circuitry. Basic soldering and wiring skills are required for secure and reliable installation. This CN3791 MPPT solar regulator controller module provides a practical, compact solution for optimizing singlecell lithium charging from small solar panels or DC sources with inputs of 5V, 6V, 9V, or 12V. It is suitable for portable chargers, remote sensors, and DIY power projects that need consistent charging performance in changing light conditions.