Solar energy is one of the most sustainable and environmentally friendly ways to generate electricity. A solar power bank uses a small built-in solar panel to charge a rechargeable battery (usually a lithium-ion battery). The panel is a photovoltaic cell which is sandwiched between a semi-conductive material (usually. So now you know to re-charge the battery, we need to get as many photons hitting the solar panel as possible to increase the likelihood that an electron will be knocked out of the field to be used in the battery. The sun's intensity varies. The reality with solar power banks is that you will be moving around a lot whilst using them. Many people like to attach them to a backpack for example. The answer is yes, it will still charge in indirect sunlight but nowhere near. A common misconception is that a solar panel will still charge on a hot day, even when in the shade. This comes back to the thought that heat is used. Clouds have a similar effect to objects causing shading. They prevent as many photons from reaching your panel. Therefore, the same as in.