GOALS: To create a solar powered USB charger that can provide more power in a shorter timeframe than those currently on the market. This device must be small enough to carry in a coat pocket, and able to recharge itself faster than a charging cell phone can discharge it. In other words, it should be able to run a cell phone non-stop without ever turning off the phone - even in overcast weather and at night. And it should be affordable for average cell phone users.
BACKGROUND: This idea began as a spin-off of my remote webcam project. The goal of that project was to develop a security camera that could be placed in a location with no electrical service and no WiFi. And while I easily solved the WiFi problem, I discovered that most currently available solar batteries are too weak to maintain the camera at night and in stormy weather. After several discussions in online forums, I learned that many people have a related problem of needing to charge cell phones but finding solar chargers to be too slow or to be unable to hold a charge for long periods of time. As a result I started this new project with the aim of building an affordable solar powered USB charger that recharges itself faster than a cell phone can discharge it.
A commercial solar charger with battery that I originally used for my remote camera project. Unfortunately it required four hours of sunlight for every hour of use, and the battery couldn't hold enough charge to last through even a few hours of darkness.
1.The first step in this project is to find an efficient and affordable solar cell. Ultimately this is going to be the source of all of the energy in the unit, and so it needs to be able to keep the current flowing. My cell phone draws about 2W maximum when charging, and since I want this unit to run even in less than ideal conditions I am looking for a panel that can generate at least 5W of power. It must also be small and affordable.