Researchers at the Massachusetts Institute of Technology have found a way to extend the power life of mobile computers. Instead of using batteries, they draw power from an electronic device called an ultracapacitor. The approach is still several years away from being used as the main electricity source for commercial laptops and handhelds, but is already used for backup power in many small consumer products. The old Palm III used an ultracapacitor to retain its memory while the AA batteries were changed.