CN3791

The CN3791 MPPT Solar Li-ion/LiPo Charging Board is a compact module built around the CN3791 IC. It functions as a switch-mode (buck) charger, specifically designed for single-cell (3.7V) Li-ion or LiPo batteries, charging them to a full 4.2V. The 'MPPT' functionality typically involves holding the solar panel near a set voltage using a resistor divider, which is a form of constant-voltage MPPT. This differs from basic linear chargers that can waste power as heat and may not perform optimally with solar input.

This board is suitable for DIY projects where efficiency is important and a simple way to charge a single lithium cell from a small solar panel is needed. It is important to note that many vendor boards may not include proper load sharing (power-path management), meaning separate battery protection and low-voltage cut-off circuits might be necessary for critical applications. The input voltage range and maximum charge current can vary significantly between vendors.

Avoid using this board for charging anything other than 1S lithium chemistries, such as LiFePO4 or 2S packs. It is also not ideal for applications where a stable system output is critical while charging, as many modules function solely as chargers. Always ensure proper wiring and consider fusing the battery for safety.