I'm not quite sure what you mean by "without alternator powered on." Nevertheless, your charging over 1 volt higher than I am. I can't imagine where I am losing the power. In your opinion, is 13-13.2 sufficient to charge and not leave me stranded? Do you have any other places I can check? The test on the alternator showed 15 volt output that was a needle bouncing, I have a digital readout on mine. Thanks