I have been using it on the dashboard of my van whilst I'm at work. And again through a window in the late afternoon. I'm getting about 4,500 mAh in a afternoon from it. I'm not sure but I find it works better horizontal, so the lines on solanoid horizontal to light. The conditions are not great. It a great size.
The usb port is just a little loose, but still connects and works as it should. 8w is what it is so don't expected huge charging speeds. It's a solid 4 star, abit more 4.5 star.
I'm a h...