skipro3 the bottom of your battery box should have an opening the same size as the opening on the lid of the battery box. Using the same size tubing as the top vent, it is routed to the vent opening on the back wall of the camper. The bottom vent configuration is the same as the top.
When I installed my second battery box I had to remove the front section of the camper bottom to attach the tubing to the rear vent. Removing the bottom was no big deal, just a lot of unscrewing.
I wish I could send you pics but I have not mastered that skill yet. Sorry.
