Hydrogen is angry. It wants to fly straight up and will straight-arm other atoms on it's way out. So a clothes-dryer size vent tube is utterly silly. When batteries evolve gas the gas is of elevated temperature. So using the process of convection the exit hose should be as high as rationality permits, and inlet vent should be the same except located at a low point. A one and one half inch hose is more than adequate for eight golf car batteries. But mind you the exit hose must be at the extreme upper elevation of the compartment. A laminar layer of four inches of stoichemetric hydrogen makes for a formidable explosion. That compartment would have feature an airtight space for the hydrogen to concentrate. But huge ducting is not in the program.