Solar charger employs solar energy to supply electricity to devices or charge batteries. They are generally portable.

Solar chargers can charge lead acid or Ni-Cd battery bank up to 48 V and hundreds of ampere-hours (up to 400 Ah) capacity. For such type of solar chargers, generally intelligent charge controllers are used. A series of solar cell array plates are installed separately on roof top and can be connected to battery bank. Such arrangement can also be used in addition to mains supply chargers for energy saving during day times.
Most portable chargers can obtain energy from the sun only. Portable wind turbines are also sold. Some, including the Kinesis K3, can work either way. Examples of solar chargers in popular use include:

• Small portable models designed to charge a range of different mobile phones, cell phones, ipods or other portable audio equipment.
• Fold out models designed to sit on the dashboard of an automobile and plug into the cigar lighter, to keep the battery topped up whilst not in use.
• Torches, often combined with a secondary means of charging, such as a kinetic charging system.

[edit] Solar chargers in the market

Solar chargers mainly uses crystaline solar panels to generate energy. Crystaline solar panel offers best energy transfer efficiency of about 15-18%. There are other solar cells like amorphouse and flexible thin films that can be used for much less efficiency. Flexible films, such as power film, are good to use in certain circumstances because of its versatility but for higher cost. Solar chargers are mostly used to charge cell phones, and mobile electronics on the go.

Most of the solar chargers came with a battery in the middle before it's used to charge external electronics. The built-in battery saves the energy generated from solar panel, and use that energy to charge cell phones.There is certain amount of energy lose during two transfers (solar panel to built-in battery; built-in battery to cell phone's battery) between.
Without a battery in the middle, the solar panel could charges external devices directly. However, it does require a stablizer and circuit changes to allow the solar panel to charge a certain device.
Solar chargers can be rollable or flexible and are manufactured using thin film PV technology . Rollable solar chargers can include batteries (generally, Li-ion). ^[1]