What's the 4-bar +/- battery symbol above the Hybrid battery meter on the MSD? My Hybrid battery meter on the MSD works fine on my 2007, lighting up in different colors as the bars go up and down, but just above that is a smaller set of 4 bars with a tiny + sign on one side and - sign on the other. These 4 bars always remain black. Does this show the accessory battery? And does it only light up when there are problemes with it? Thanks!