I uses a passive venting system for the battery box. The battery box hold (4) 6 volt deep cycle batteries. It is wire for a the volt system. The box was constructed from f/8″ Birch plywood and painted white. The lid can easily be flipped open and closed tightly. I have added a seal around the outside of the lid. For me, it’s just a piece of mind that something can function without moving parts. The venting system was made up from 3/4″ – 1-1/2″ PVC pipe that was dry fitted together. The large 1-1/2″ pipe for the rising hydrogen and the small 3/4″ fresh air pipe running to the bottom. It creates a vacuum inside the box and doesn’t need electricity to work.
The batteries appear dirty because they bubbled over and the acid had to be neutralized with baking soda.