Cell phones have to be charged to be functional, and most people use a wall outlet adapter, and possibly a car adapter, to keep their phones charged. People who are going to be "off the grid" for a period of time, as well as those with strong environmental concerns, find other methods. Possibilities include a wind powered phone charger, a wind-up phone charger, and a solar phone charger.
A solar phone charger works the same way as a solar light: sunlight is converted into electrical current. As photons fall onto the solar cell, electrons become more active. This causes a flow of electricity, which is harvested. The sunnier the day, the more electricity is produced. This electricity can be stored in a battery for later use. Generally, 60 minutes of sun will produce enough power for four days of standby time or ten minutes of talk time on most phones.
In one kind of solar phone charger, the electricity is stored in the phone's battery, just as if the phone was plugged into a wall outlet. In another kind of solar phone charger, the electricity is stored in a separate battery. It is later transferred from the storage battery to the cell phone battery.
Often a solar phone charger can be used to charge a variety of small electronic devices, not just a phone. With the proper adapter, a solar phone charger could also be used to power an MP3 player, a GPS, or a Walkman as well as a standard cell phone. In some designs, several solar phone chargers can be used together to power a larger device, such as a PDA or a laptop.
Most solar phone charger designs are small and lightweight. One popular design has three rectangular panels, each three inches (7.62 cm) long, joined together at one end. The panels are fanned out and laid in the sunlight to generate power. Another popular design looks like a compact mirror when closed and opens with two circular panels that gather power.
The drawback of a solar phone charger, of course, is that it cannot generate electricity at night and generates very little electricity on cloudy days. Many solar phone chargers, especially the ones with their own batteries that are used to power a variety of small electronic devices, can generate and store power from other sources. Small wind-powered chargers are available. So are wind-up chargers, which work the same way as wind-up flashlights. Of course, in some designs, a solar phone charger can also store electricity drawn from a wall outlet or a car battery.