I have four battery boxes on the front of my POPUP deck and I drilled holes in the bottom of the boxes for draining. They do however drain straight to the ground. I am planning to install a larger diamond plate lock box for my batteries and will probably not drill holes in the bottom to drain off water since no water will be able to get inside from the closed lid or battery fume vents. I also use smart-mode charging and haven't seen any boil-over now for a few years. My batteries will probably be sitting in the bottom plastic holder when I re-install them in the metal lock box.
Roy and Carolyn
I claim Horse Creek Country in Southern Ill - Momabear is from North Texas
We live in King George VA
RETIRED DOD DOAF DON CONTRACTOR Electronics Tech 42YRS
"We're burning daylight" - John Wayne
2008 STARCRAFT 14RT OFF-ROAD POPUP with PD9260C and three 85AH 12VDC batteries
2010 F150 FX4 5.4 GAS with 3.73 gears - Super Cab - Towing Package - 2KW Honda EU2000i Gen
K9PHT (since 1957) 146.52Mhz
"We always have a PLAN B"