In my earlier schematic (V1.0), the solar panel is the only source to charge the battery. However, due to the limited area of the lamp, the solar panel mounted on the lamp is not sufficient to charge the larger capacity battery. So I have added a USB port (Type-C) to charge the battery faster. You can use an external solar panel or any USB source to charge the battery. It is also useful for sunny days when the panel doesn't receive sufficient solar radiation.

New Schematic:

Details of USB-C Port :

I am using the vertical mount USB port as shown in the below picture. The dimensions are D=10.0, E=5.0, and F=7.90.

The pinouts are  as tabulated below: