Larry, looking at the manual for the Sunsaver MPPT it states "The solar module(s) nominal voltage must be equal to or greater than the nominal battery voltage." I'll bet you have a longer charging day now than you did running on 12V out of the panels. When the panel voltage drops below the charge voltage you get nothing. Now that you are running on 24V nominal you can get partial shading or cloud cover and still stay above charge voltage. Add that to the 1V you save due to current reduction and it should have a noticeable impact.