Unfortunately I have had no success with this solar charger. I acknowledge that I have only tried to charge two cell phones, one via the USB port and the other through the built-in adapter. However, neither one charged to any noticeable degree. While Indiana winters do not supply a surplus of sunshine, I attached the charger to a south-exposed window with suction cups and failed to get results on nearly 100% sunny days. In fact, once the phone ran out of juice on me and in every case the battery indicator stayed the same or dropped. Of course, the phone was on and thus using some battery charge, but to only maintain the charge, at best, is unacceptable. I have a coil/shake flashlight and a crank flashlight, so I desire to utilize renewable energy, but it has to work and I can't recommend the product when it can't charge a cell phone with its relatively low consumption/demand.