FORD 2010 F-550 v.2 - Manual (Page 80)

To install the batteries, remove the screw at the bottom of the cover.
Then, lightly press down on top and slide the cover off.
When replacing the batteries, use two new batteries (alkaline
recommended) and install them with the correct orientation as indicated
in the battery housing.
Entertainment Systems
80
2010 F-250/350/450/550 (f23)
Owners Guide, 2nd Printing
USA (fus)