Garrett Metal Detectors Sea Hunter Mark II None - Manual (Page 28)

BATTEry rEPLACEMENT
To access the battery pack, unscrew the
battery cap at the rear of the detector
housing, by hand. Do not use tools.
The o-ring should remain in the control
housing while the battery pack slides
out. When installing batteries ensure that
they are aligned with the correct polarity
(plus and minus) markings. Re-install the
battery pack by placing the contact end
of the housing inside first and pointing
downward (figure 8). Verify that the o-ring
is well-lubricated and free from debris.
Add a little silicon grease or petroleum

Figure 8, Proper battery pack re-installation