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Ventilation: Suck In or Blow Out????

3036 Views 42 Replies 24 Participants Last post by  vbiz59
Heading into a tropical summer and want to ventilate the battery bank. Its a box under the bed in the aft cabin, no real venting except one 6 x 6 inch hole at one end. Air seepage the other end.

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Sooooo is it better to suck in cooler air? Or blow out the hotter air?​


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Exhaust and pull fresh air from the cabin... exhausts to the bilge/cockpit lazarettes
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If you are ventilating due to potential fumes such as batteries gassing or engine compartment odors then you want to maintain that compartment at a negative pressure. If you blow into it and create a positive pressure you will force those fumes and odors to migrate throughout the boat.

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Depends on boat architecture. My batts sit aft of the engine... above the bilge... I exhaust into the bilge. I have a bilge blower which exhaust bilge air.
My battery compartment has a blower which pushes air in and a 3" diameter hole and several smaller holes which allow the air to exit into assorted bilge areas which ultimate are interconnected... more or less, There are a few outlet louvers... one in the coaming bin and the other on the transom.
Im in the tropics this summer. In the hurricane season theres not much in the trade wiinds. So the aft cabin doesnt get much cooling. Cooler batteries are much more efficient. Thats whey theres a batter temperature sensor to change the charging voltage. I think in Grenada they could lownly heat over a few weeks and be quite hot, soooo its just to have some air movement in a small space. Just knocking those top few degrees down might be well worth it.


Even in summer my battery compartment and the bilges are pretty cool... probably because the water temp is much cooler than the air temp.
My batts are sealed but I suppose they do produce some gas. It is exhausted into the bilge with a small fan via a 3" diameter hole. There are multiple large diameter holes at the top of the batter box for passing wires/cables and.... gases. As the boat has adequate ventilation I am not concerned about noxious gas. I have a gas sensor / alarm as well.
You'd lose the bet.
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