Agreed. Note that the Anker battery specs indicate that it's expecting an input at 5V, 1.5A; i.e. 7.5W whereas the solar panel is spec'd with an output of 6W - and that's probably under really optimum conditions (summer noon with the panel facing the sun and no haze). No idea what this particular battery pack will do if it doesn't get the full 7.5W. Some will just not charge at all while others might charge but at a slower rate. Unless you can do some tests or find a reliable review that has done some you're better off going with a battery pack that at least says it's designed for the variable power you get from a solar panel.