ummm...with an extra battery, you would usually take it out tocharge it... so vapors would not be an issue... and the yellow top DOES NOT need venting when in use... now if you find away to hook up an alternator, which is bout impossible, then you would need a vent...LOL, not taking sides just showing you that you weren't thinking it through all the way... it's okay tho guys, everyone has
brainfarts....lol
