Given the panel seems to have its output to a standard USB A socket, I would venture that it contains a 5V regulator in it already. At a mere 6 Watts of output, charging anything is going to need a lot of light and a good amount of time. Photovoltaic cells can draw current in low or no light situations, but if it does have a regulator on-board, the regulator will prevent reverse current draw. It's hard to tell from the picture, but it looks like the PV cell is amorphous silicon rather than crystalline silicon where amorphous has a lower output efficiency but is a little more durable over crystalline Si. The sunlight is free, but don't expect much from this cheap chinesium panel.
Given the panel seems to have its output to a standard USB A socket, I would venture that it contains a 5V regulator in it already. At a mere 6 Watts of output, charging anything is going to need a lot of light and a good amount of time. Photovoltaic cells can draw current in low or no light situations, but if it does have a regulator on-board, the regulator will prevent reverse current draw. It's hard to tell from the picture, but it looks like the PV cell is amorphous silicon rather than crystalline silicon where amorphous has a lower output efficiency but is a little more durable over crystalline Si. The sunlight is free, but don't expect much from this cheap chinesium panel.
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