THERE ARE a few things one can expect with confidence from a day at Portland International Raceway: the roar of engines, the smell of diesel, maybe a satin jacket or two. But not when the race-day event is called Electrathon America, held May 24 to 26, during which drivers rip silently around the track in vehicles powered not by high-performance fuel but by two 12-volt batteries. (OK, we can’t promise there won’t still be a few satin jackets.) “Ripping” might be an exaggeration, since the fastest low-slung, one-man electric cars top out at a little over 50 mph; the goal is to complete the most laps in one hour without recharging, making it a race for efficiency rather than for speed. About 20 teams competed last year, including one Hawaiian squad who, in 2006, had to pack their ride, one piece at a time, in their carry-on luggage and reassemble it on the mainland. Not that the reassembly was any kind of a setback: They still took first place.