People who are trekking in the wilderness, stranded at disaster sites or living in developing nations all have one thing in common - lack of access to an electrical infrastructure. Solar charging devices such as the Solio, iCharge and Joos Orange have been designed to meet the needs of some or all of these groups. One of the latest such systems, Horizon Fuel Cell Technologies' Sunbox USB 3.0, is particularly versatile.

The Sunbox gathers solar energy through a 1.8-watt waterproof photovoltaic panel. Whenever the sun is shining, that panel automatically starts charging the power system module, via a 3-meter (9.8-foot) cable. That module incorporates a 6-volt 3,000 milliampere-hour battery, two USB ports, and an LCD screen that displays the battery's level of charge. A full charge requires 6 to 10 hours of sunlight.

A 25-LED, 2-watt lamp can be plugged into the module's top USB port, for ambient nighttime lighting. For more focused lighting, an LED spotlight with a 3-meter cord can be plugged into either port. If you need a more mobile light source, there's also a 1-watt LED flashlight head that plugs into the top port.

The power system module can additionally be used to charge mobile devices such as cell phones, most models of which should work with one of the seven adapter tips that are included. If you're trying to power a device that doesn't have a built-in battery pack (such as a radio), there's also a charging cradle that includes two rechargeable AA batteries. Should you wish to charge up the module using a source other than the sun, the system comes with a 14-volt DC charger plug.

The Sunbox USB 3.0 package is available for US$199.99, from the Horizon website.

Readers involved in foreign aid might also be interested in Horizon's entrepreneur package. It allows small businesspeople in developing nations to charge ten Sunbox battery packs at once, which can then be rented out to members of the local community.