What do you mean by 'proper'?...It is ok to have them under a bunk, just make sure you have a proper ventilation system set up.
ABYC Master Tech.
a. Venting out of the battery box into the under bunk area?
b. Venting out of the under bunk area into the living space?
c. Venting out of the box directly overboard?
d. Venting out of the under bunk area overboard?
e. Something else?
My boat has had batteries under the bunk since 1985, as designed by the factory. Am I about to die?