Help! Slow Battery Discharge

Everyone may have missed this and I may have misread but if you are on volts scale and you are reading 13 volts between your negative battery post and vehicle ground... you have a super ground problem and more like a very poor grnd, almost a open circiut. THAT needs to be resolved first.

Thank you all for the posts and ideas. I have not been able to get back on this issue as I have been chasing a vibration issue. I'll do some more testing this coming weekend and make a post.