I was just charging my Li-ion battery manually with my IP2312 charger, the high current version I have made previously. Then the idea of charging batteries with solar with an automatic cut off option comes to my mind. What I can do is simply hook this IP2312 charging module with solar with a diode in series for reverse voltage protection. But this seems a very unprofessional and inefficient idea. And I found CN3165, a solar powered MPPT based single cell battery charging IC with protection features. I searched for some web documents and found this amazing DFRobot Solar Power Manager board based on the same IC.

The module comes with integrated MPPT (Maximum Power Point Tracking) to maximize solar energy conversion efficiency under various sunlight. Onboard integrated circuit based battery and power protection features which provide reliable power management for different types of solar projects.

I have designed a custom solution based on the IC which have same IC but in the same form factor of other boards, I think it will be better solution to other available battery chargers. PCBWay is the best solution out there I found for PCB fabrication. They offer a low-cost, highly reliable, and foolproof process from prototype to full-scale product manufacturing. With quick turnaround times, extensive material options, and exceptional customer support.

Schematics:

The schematics has 5 sections,

First section is based on the DW06D IC, which protects the battery from overcharging and over discharging; the same protection feature can be found in typical TP4056 Li-Po charger boards.

Second section is based on CN3065, the main hero of this board. It comes in many variants, having the same pinout (CN3065/CN3165). This thing gets the input either from solar or from on board micro-USB seen in the last section of the schema. Some input output decoupling capacitor, led indicators, and current setting resistor completes the section.

Third section is a standard solar interface that comes with an indicator, which helps to find out if there is any power available or not from solar input.

Fourth section is a typical booster section containing an MT3068 booster with SY6280 current protection unit. This thing boosts up the 3.7V battery to 5V, to power up an output USB port and some onboard headers.

Fifth section contains input/outputs USB and power headers.

Modified Schematics of the Board: