You’ve already been corrected. But just to state it again, yes, AGM batteries do in-fact require venting. Sure, they may be maintenance-free, but the hydrogen gas needs to go somewhere in case of overcharging.What? No. They are 100% completely sealed. They dont need to breath much externally as they dont really heat up much at all. The entire reason for AGM is to NOT dump acid into a lake when your fishing boat tips over.