Sealing the battery box?

[captainrivet]

Why you need to keep space and openings in the enclosure to breath for the cells?
I see that in many build threads mentioned
In drop ins (saw in many cut opens there is no space till 1-3cm) they are sealed and sometimes even encapsulated in glue or resin and they just have a little opening for pressure equalization or a valve. This is to minimize vibrations, corrosion and oxidation on all parts.
I have 3p4S Lishen cells.why the eve or lishen or alike build prismatic cells should be different in that matter?
I plan to build a box of nylon boards, due to space constrains I have 3cm between top of the cells and top of the box.
i also plan seal the battery enclosure and just leave two openings where the main battery cables come out as it is used in marine environment on a cat.

 

[stienman]

Ideally cells don't vent.

In the real world they do - sometimes rarely, and sometimes only when used outside their operating parameters - but they all can and do generate gases.

There are two issues with these gases:
1. Most are flammable and pose a direct fire/heat/explosion hazard
2. The build up of pressure will eventually result in enclosure failure. This failure is considered an explosion if it occurs fast enough.

If you choose to seal a chemical reaction (ie, battery) and don't account for conversion into gas and the resulting dangers then you will eventually have A Very Bad Day™.

 

[captainrivet]

That why I said I seal it but leave 2 holes, one at each end where I root out the main cable so pressure can‘t build up and if the gasses are heavier then air they stay inside the box, if not they evaporate through the two holes. And this cannot be much as the lifepo4 considered to be able installed in closed spaces.
but they don‘t need space& air for operation to cool or breath as others write.
Tear down of a 200AH Victron battery shows it consists of 4 Winston 200AH cells, BMS and a sealed plastic box with an overpressure valve that is 6mm in diameter, That’s all. So the gases stay untreated in the battery till they create so much pressure that this valve blows. Which is normally the case if one cell is overcharge And blows out a big amount of gas. In normal operations nothing, it’s sealed.
The old Victron are completely sealed, no valve and the case bloates and cracks if it gases.