FORD 2011 Edge v.3 - Manual (Page 366)

To ensure proper operation of the battery management system (BMS),
any electrical devices that are added to the vehicle should not have their
ground connection made directly at the negative battery post. A
connection at the negative battery post can cause inaccurate
measurements of the battery condition and potential incorrect system
operation.
• Any non-Ford electrical or electronic accessories or components that
are added to the vehicle by the authorized dealer or the owner may
adversely affect battery performance and durability, and may also
adversely affect the performance of other electrical systems in the
vehicle.
Accessories
366
2011 Edge (edg)
Owners Guide, 3rd Printing
USA (fus)