Don't be too quick to toss out the battery from that ancient laptop -- it might just be the key to powering homes in developing countries, and helping the environment in the process. IBM researchers have revealed UrJar, a device that turns old lithium-ion battery packs into rechargeable energy sources for low-power devices like LED light bulbs, fans and cellphones. To create the gadget, the team extracts functioning lithium-ion cells from a trashed battery and combines them with both charging dongles and safety circuitry. It sounds simple, but it's potentially very effective. According to IBM, roughly 70 percent of all discarded batteries can provide at least four hours of LED lighting every day for a year. That's enough to offer extra safety to homes in areas with little to no reliable electricity, or to keep a street vendor in business after sunset.