OK the voltage you measure--whatever it is--ADDS to the VR setpoint. So "let's say" that after warming up, the VR is at 13.8. That .65 adds to the VR setpoint and "in theory" (and if there is no drop in the ground side) the VR will run the battery to 13.8 + .65 = 14.45. Now that is not "terrible" and if that is true there might be something else wrong. The VR might be out of spec which is not common but can happen. There MIGHT be drop right at the VR terminals/ connector. If you order yourself a rifle cleaning brush for .177 (bb gun/ pellet size) that will fit inside those connector terminals.