Battery tech starts catching up to high tech.
WATERTOWN, MASS. - Standing at the base of a gym's climbing rope, Nathan Ball checks his harness and prepares to live every gym student's dream. He flicks a switch on his "rope ascender" and zips up to the 45-foot ceiling in less than five seconds. The 15-pound battery-powered device, designed by Mr. Ball and three fellow Massachusetts Institute of Technology students, can hoist 250 pounds at 10 feet per second (about 7 miles per hour).