Why do solar panels charge so slowly?

Here are some ways to potentially speed up the charging of your solar panels

1.90 degree postion facing the sunlight
2.all the solar panel face to the sunlight towards the same direction
3.we recommend our customers to charge the OUPES generator with the OUPES solar panels.
It will achieve the maximum power input.
4.no obstruction, even a leaf may affect the charging efficiency
5.maybe the solar panel is aging so the working efficiency is low