I had a chance to do a 120 km round trip, mostly highway, yesterday, with a voltmeter hooked up through the lighter. On the way out voltage was consistently 14.05 or thereabouts. When I went through a very slow section of town voltage suddenly dropped to 11.5 and battery light came on. After a long stop, on the way back, voltage read about 13.9 all the way, with no stops.